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Open Access

Peer-reviewed

Research Article

Hamstring strength assessment methods in sport: A systematic review and meta-analysis of post-activity strength decrements, asymmetry benchmarks, and measurement reliability

  • Adam E. Sundh ,

    Roles Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Visualization, Writing – original draft, Writing – review & editing

    A.Sundh@edu.salford.ac.uk

    Affiliations School of Health and Society, University of Salford, Salford, United Kingdom, Chicago Bears Football Club, Lake Forest, Illinois, United States of America

    ⨯
  • Nicholas J. Ripley,

    Roles Conceptualization, Data curation, Investigation, Methodology, Project administration, Supervision, Writing – review & editing

    Affiliation School of Health and Society, University of Salford, Salford, United Kingdom

    ⨯
  • A. J. Lamb,

    Roles Investigation, Methodology, Project administration, Supervision, Writing – review & editing

    Affiliation Chicago Bears Football Club, Lake Forest, Illinois, United States of America

    ⨯
  • Paul Comfort

    Roles Conceptualization, Data curation, Investigation, Methodology, Project administration, Supervision, Writing – review & editing

    Affiliations School of Health and Society, University of Salford, Salford, United Kingdom, School of Medical and Health Sciences, Edith Cowan University, Joondalup, Australia

    ⨯

Abstract

Hamstring strain injuries (HSI) represent one of the most prevalent and recurrent injuries in sport, making reliable strength assessment essential for neuromuscular monitoring in athletic populations. Despite the breadth of available testing modalities, no comprehensive synthesis of assessment methods, their reliability, post-activity strength responses, or normative asymmetry values has been undertaken. This systematic review and meta-analysis aims to evaluate the reliability of hamstring strength assessment methods, quantify the time-course of strength decrements following competition, establish normative inter-limb asymmetry benchmarks, and identify gaps to guide future assessment practices. PubMed, Scopus, SPORTDiscus, and Web of Science were searched from inception to November 1, 2025 following PRISMA guidelines. Methodological quality was assessed using a modified version of the Downs and Black checklist. A total of 161 studies were included in qualitative synthesis and 106 in quantitative analysis. Isokinetic dynamometry was the most frequently used modality, followed by force platform assessments and Nordic hamstring-based devices, with a clear upward trend in field-based testing observed after 2010. Multiple modalities demonstrate good reliability, sensitivity to post-activity fatigue, and comparable patterns to detect inter-limb asymmetries, supporting their use across varied applied settings. Hamstring strength deficits persisted for 24–72 hours following on-field activity, identifying a critical vulnerability window during congested schedules. Minor inter-limb asymmetries of approximately 3–4% appear normative and should not be considered clinically meaningful in isolation. Practitioners should establish individualized baselines and integrate routine monitoring with evidence-based recovery strategies to mitigate HSI risk throughout competitive seasons.

Citation: Sundh AE, Ripley NJ, Lamb AJ, Comfort P (2026) Hamstring strength assessment methods in sport: A systematic review and meta-analysis of post-activity strength decrements, asymmetry benchmarks, and measurement reliability. PLoS One 21(7): e0352509. https://doi.org/10.1371/journal.pone.0352509

Editor: Esedullah Akaras, Erzurum Technical University: Erzurum Teknik Universitesi, TÜRKIYE

Received: April 21, 2026; Accepted: June 11, 2026; Published: July 21, 2026

Copyright: © 2026 Sundh et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All data are fully available without restriction; All relevant data are within the paper.

Funding: The author(s) received no specific funding for this work.

Competing interests: The authors have declared that no competing interests exist.

1. Introduction

Hamstring strain injuries (HSI) are among the most common non-contact injuries in team and field-based sports, including American football [1], Australian rules football [2–4], soccer [5], rugby union [6], and track and field [7]. Despite growing evidence that targeted interventions may reduce HSI incidence [8,9], injury rates remain high. Key risk factors include hamstring strength [10], particularly eccentric, and biceps femoris long head (BFLH) fascicle length [11], both modifiable through training to potentially reduce injury risk [12] and enhance sprinting and jumping performance [13–15]. Additional risk factors, including previous HSI [16], age [16], high-speed running exposure [17,18], and high-intensity accelerations [19,20], are largely unmodifiable under competitive demands, highlighting the need for continuous monitoring of modifiable risk factors.

Given its influence on muscular function and subsequent role in HSI [21–23], BFLH fascicle length has been a major research focus [11,15,24,25]; however, ultrasound-based monitoring is technically demanding, time-consuming, and difficult to implement at scale, often requiring estimation methods that can overestimate fascicle length [26–28]. Despite generally acceptable reliability [29], these limitations highlight the need for simpler, efficient, and field friendly alternatives for monitoring fascicle length in applied sporting environments. Hamstring strength assessments thereforeoffer a practical alternative for evaluating modifiable HSI risk factors across diverse settings. While not a direct proxy for morphological measures such as FL, strength assessments capture distinct functional capacities that may independently contribute to HSI risk. Various hamstring strength assessment modalities may provide unique insights into strength characteristics [30–32], although heterogeneity in joint angles, positions, devices, and targeted muscle activation, alongside evidence that some assessments are not interchangeable even within the same contraction mode, may complicate interpretation [30,33,34]. Despite the breadth of research in this area, no comprehensive review has compared these methods for reliability, feasibility, and practical implementation in high-performance sport.

As such, the purpose of this systematic review is to provide a comprehensive overview of the current methodologies, identify research gaps, and offer recommendations to improve assessment practices. By synthesizing information on commonly used hamstring strength assessments, including alternatives to laboratory-based methods, this review aims to inform practitioners about the time-course of hamstring strength loss following exercise or competition, and the reliability and sensitivity of various assessment methods, thereby supporting evidence-based decision-making in applied, high-performance sport. Additionally, where available, inter-limb asymmetry data will be examined across commonly used hamstring strength assessments to provide pooled estimates, offering practitioners a reference for benchmarking and facilitating the interpretation of results in both research and applied sporting environments.

2. Methods

2.1 Study design

This systematic review was conducted while adhering to the 2020 Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. The PRISMA guideline statement features a 27-item checklist intended to serve as a foundation for reporting systematic reviews and meta-analyses [35]. The review protocol was pre-registered through the International Prospective Register of Systematic Reviews (PROSPERO; CRD42025571001).

2.2 Literature search

A comprehensive literature search was performed using Boolean search terms related to hamstring strength or force-production characteristics across the PubMed, Scopus, SPORTDiscus, and Web of Science databases. The search was conducted from inception to November 1, 2025. The search strategy was developed to target studies assessing hamstring strength, force, and related performance outcomes using isolated or global posterior chain assessments. Summarized keywords were grouped into three domains (Table 1) and were selected to reflect the research objectives. Boolean logic was applied to combine the search terms, using AND, OR, and NOT categories. Additionally, reference lists of included studies were manually screened to identify any potentially relevant articles not captured by the database search.

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Table 1. Overview of keyword groupings utilized in database searches.

https://doi.org/10.1371/journal.pone.0352509.t001

These combinations were used to ensure relevant variations in terminology and testing modalities were captured across databases. The following Boolean search string was applied, with minor adjustments depending on database-specific syntax:

(“Hamstring” OR “posterior-thigh” OR “posterior-chain” OR “knee flex*” OR “hip exten*”) AND (“eccentric” OR “concentric” OR “isometric” OR “dynamometry”) AND (“force” OR “torque” OR “acute” OR “fatigue” OR “changes” OR “monitoring”) NOT (“injury” OR “weeks” OR “seasonal” OR “longitudinal” OR “electromyo*” OR “imposed” OR “twitch”). Field-based and device-specific studies were captured through both generic search terms and citation tracking of included records. Detailed search criteria for each database are provided in the supplementary materials.

2.3 Inclusion and exclusion criteria

Studies were eligible for inclusion if they met all of the following criteria: (1) randomized controlled trial, cross-sectional, observation, methodological, or acute experimental design; (2) participants were team, field, or individual sports athletes at any competitive level; (3) participants were adults ages 18 years or older [36]; (4) participants were healthy individuals of any gender, with no lower extremity injury in the past 6 months or major injury (e.g., ACL tear) in the past 12 months; and (5) the study focused on acute force production characteristics, such as pre-season screening, pre/post fatigue assessments, or reliability testing.

Studies were excluded if: (1) the study was a long-term intervention examining training adaptations; (2) participants were not involved in any structured or competitive sporting activity; (3) participants were under 18 years of age; (4) participants were injured or undergoing rehabilitation; or (5) the study was longitudinal in nature, defined as lasting longer than one week.

2.4 Assessment of methodological quality

Methodological quality was assessed using a modified version of the Downs and Black checklist [37], which evaluated reporting quality, internal validity, statistical power, and external validity across randomized and non-randomized studies. Twelve items from the original checklist (items 1–4, 6, 7, 10, 11, 16, 18, 20, and 27) were selected as most relevant to this review’s aims, following the approach of previous systematic reviews [38–40]. The remaining items were excluded as they were deemed irrelevant to the observational and reliability study designs mainly included in this review. Item 4 was interpreted as whether the study procedures were clearly described, item 10 as whether p-values or effect sizes were appropriately reported, and item 27 as whether sample size or statistical power was evaluated. Each item was scored as 1 (criteria met) or 0 (criteria not met or unclear), resulting in a maximal score of 12. Studies were categorized as excellent (11–12), good (9–10), fair (6–8), or poor (0–5), adapted proportionally from established classification bands [41,42].

2.5 Study selection and data extraction

Titles and abstracts were independently screened by two reviewers (AES and NJR), with conflicts resolved by a third reviewer (PC). The same procedures were followed for full-text screening, while data extraction was conducted by one reviewer (AES). Extracted data included study design, bibliographic details, participant characteristics (sample size, age, competitive level, sport), assessment protocol details (device, contraction type), outcome variables with reported values (means, standard deviations, ranges), and reliability metrics including intraclass correlation coefficients (ICC), coefficient of variation (CV%), standard error of measurement (SEM) and minimal detectable difference (MDD). Competitive level was extracted as reported by the original study authors; where not explicitly stated, supplementary sources such as publicly available information pertaining to the relevant league or governing body were consulted to inform classification.

Data were synthesized with subgroup analyses pooled across relevant study and participant characteristics, except where subgroups represented distinct, non-comparable populations (e.g., differing by sex or sport), in which case they were analyzed separately. Subgroups reflecting within-population characteristics (e.g., playing position) were considered comparable and pooled. Where effect sizes were not reported, they were calculated from available summary statistics, when outcomes were reported relative to body mass, absolute values were estimated by multiplying the ratio-scaled mean by mean body mass, with standard deviations estimated via error propagation. Where post-publication corrections were identified, corrected values were used in place of originally reported data.

2.6 Meta-analysis

Meta-analyses were applied to examine changes in hamstring strength following on-field activity across different muscle actions (e.g., concentric, isometric, eccentric) and recovery time points, with the aim of quantifying the fatigability of the hamstring musculature. Where intervention studies were included, only pre-intervention or control condition data were extracted to reflect the natural time-course of strength decrements. In addition, normalized left-right inter-limb strength differences were assessed separately to evaluate expected baseline inter-limb asymmetries, which are frequently evaluated as potential injury risk factors [43], offering insight into the range of differences commonly observed and to help contextualize asymmetries. All data were extracted and pre-processed in Python (Python Software Foundation, DE, USA) before being imported into the R statistical programming language (4.2.2, R Foundation, Vienna, Austria) for statistical analysis. Specifically, Python scripting was employed to facilitate all pre-meta-analytic procedures, including data cleaning, organization, and categorization of extracted variables, calculation of effect sizes, confidence intervals, and standard errors, where not reported in the original manuscripts (derived from available statistics), as well as preparation of all summary tables, whilst R was used for all formal meta-analytic statistical procedures. Hedges’ g was calculated from pre- to post-intervention values to provide a standardized measure of effect size, accounting for differences in sample size between studies and enabling a consistent assessment of hamstring strength decrements across studies with differing assessment methodologies. Effect sizes were interpreted according to the thresholds established by Hopkins: <0.20 (trivial), 0.21–0.59 (small), 0.60–1.19 (moderate), 1.20–1.99 (large), >2.00 (very large) [44]. Meta-analyses were conducted separately for different time-course groupings (immediately post-intervention, 24h, 48h, and 72h), with mode of contraction included as a subgroup when feasible. Pooled effect sizes were estimated within each subgroup and across the total sample using a random-effects model via Restricted Maximum Likelihood (REML). Studies could contribute to more than one meta-analysis if multiple contraction modes were reported at the same time-course, but only once within each subgroup to avoid inflating heterogeneity estimates (I2). Heterogeneity was quantified using absolute (τ²) and relative (I2) measures, interpreted as low (<25%), moderate (25−75%), or high (>75%) [45]. Uncertainty in pooled estimates were expressed using 95% confidence intervals (CIs) and 95% prediction intervals (PIs) to indicate the expected range of true effects in future studies. Reliability measurements extracted from the included studies were interpreted using the following criteria: absolute reliability was assessed via CV%, interpreted as <5.00% (excellent), 5.00–9.99% (good), 10.00–14.99% (moderate), and ≥15.00% (poor); relative reliability was assessed via ICC (3,1) [], interpreted from the lower bound CI as >0.90 (excellent), 0.75–0.89 (good), 0.50–0.74 (moderate), and <0.49 (poor) [46]. Where reported, SEM and MDD were also extracted as additional measures of absolute reliability; as these metrics are scale-and device-dependent, no universal interpretation thresholds were applied. To compare how standardized effect sizes in inter-limb strength differences relate to commonly used asymmetry threshold cut-offs, individual study percentage differences were calculated as:

Individual study differences are expressed as a percentage, providing a standardized measure of inter-limb asymmetry. To account for differences in sample size across studies, the weighted percentage difference was calculated as:

Where represents the percentage difference for the individual study and is the corresponding sample size, allowing for appropriate influence of larger studies and providing an overall summary measure of asymmetry. Finally. To assess the expected range and variability of inter-limb asymmetries, the weighted standard deviation of percentage differences was calculated as:

Where represents the weighted percentage difference and the weighted SD quantifies the spread of inter-limb asymmetries across the studies.

3. Results

3.1 Identification and selection of articles

The selection process is illustrated in the flowchart shown in Fig 1. An initial database search identified 5,393 articles. After the removal of duplicates, 3,467 articles were screened based on titles and abstracts, leading to a full-text review of 438 articles. An additional 6 articles were identified through reference lists for full-text eligibility assessment. Following full-text screening, 161 articles were included in the study.

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Fig 1. Flowchart of the selection process of eligible studies.

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3.2 Evaluation of methodological quality

The methodological quality of the studies included was generally good (Table 2). No study achieved a perfect score, although 30 (19%) were classified as excellent. The majority, 109 (68%), were rated as good, while 22 (14%) were classified as fair. No studies received a poor rating, and therefore, all studies were deemed methodologically eligible for both qualitative and quantitative synthesis.

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Table 2. Methodological quality (Downs & Black assessment).

https://doi.org/10.1371/journal.pone.0352509.t002

3.3 Characteristics of included studies

A total of 6803 participants were included across all studies, 5321 (78%) male, 1141 (17%) female, and the remainder unspecified (5%). Mean age, body mass, and height were 22.8 ± 2.9 years (range:18.0–33.3), 74.2 ± 10.0 kg (range: 46.0–109.6), and 173.9 ± 18.5 cm (range: 168.2–195.7) for the total sample, male: 23.5 ± 3.1 years, 77.4 ± 10.8 kg, and 178.6 ± 14.9 cm, and female: 21.7 ± 2.4 years, 63.2 ± 6.5 kg, and 166.8 ± 4.7 cm.

Competitive level varied across studies. Most participants were professional (68 studies, 42%), followed by collegiate (28, 17%), semi-professional (18, 11%), amateur (8, 5%), and recreational (2, 1%). With 37 (23%) studies unable to be classified. Using the McKay classification tier [47] the majority were highly trained/national level (Tier 3: 78 studies, 48%), followed by elite/international (Tier 4: 49 studies, 30%), trained/developmental (Tier 2: 19, 12%), world class/Olympic (Tier 5: 3, 2%), and recreational (Tier 1: 2, 1%), with 10 studies unclassifiable (6%).

Participants were drawn from approximately 32 sports, most commonly soccer (81 studies, 50%), rugby (14, 9%), track and field (14, 9%), combat sports (13, 8%), and basketball (11, 7%), with the remaining 17% of studies spanning 27 other sports. Studies were conducted across 43 countries, with the largest contribution from the UK (25, 16%), Brazil (17, 11%), Spain (15, 9%), the United States (15, 9%), and Turkey (10, 6%), with the remaining 49% of studies originating from 38 other countries. Most studies used a cross-sectional design (132, 82%), followed by non-randomized experimental (22, 14%) and randomized control trials (7, 4%).

3.4 Aims and focus areas of hamstring strength research

Among the 161 included studies, research aims were diverse and frequently encompassed multiple areas of investigation. The most common focus was H:Q ratio (63 studies, 39%), spanning various isokinetic speeds, traditional and functional ratio types, and the relative influence of hamstring and quadriceps strength on the ratio. This was followed by studies examining relationships between hamstring strength and performance outcomes such as speed, change of direction, and jumping (48 studies, 30%), and descriptive or normative values comparing position groups, sexes, competitive level, or sport (46 studies, 29%). Additional aims included reliability of hamstring strength assessments (28 studies, 17%), the impact of fatigue on force production (22 studies, 14%), and the influence of anthropometric factors such as limb length and muscle mass (10 studies, 6%). This distribution of research aims underscores the breadth of interest regarding hamstring strength assessments, providing a comprehensive overview of context examined within sporting populations.

3.5 Assessment methods

Across the included studies, a wide range of devices and manufacturer-specific systems were employed to assess hamstring strength and performance-related outcomes. Based on methodological similarities in the assessments, these methods were grouped into three main categories: Isokinetic dynamometry (IKD), force platforms (FP), and Nordic hamstring exercise devices (NHE). Load-cell-based systems that operated in compression or pressure-based configurations, when not otherwise specified, due to their functional similarity and operating principles, were combined with force platforms. Conversely, tension-based load-cell applications were not combined with force platforms. A fourth, smaller subgroup, alternative methods, included handheld/portable fixed dynamometry and anchoring systems. While these approaches are less commonly reported and will not be discussed in detail, they are summarized in Table 6 for reference.

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Table 6. Remaining assessment devices.

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Overall, there is a clear upward trend in researchers examining hamstring strength assessments within sporting environments; this increase is particularly evident after 2010 (Fig 2). Notably, all studies utilizing field-based assessment methods were conducted post-2010, with a substantial surge after 2020. This trend highlights the growing emphasis among practitioners and researchers on identifying ecologically valid, reliable, and accessible methods that extend beyond traditional laboratory-based equipment [48,49], perhaps driven by the notable prevalence of HSIs in team sport [5] and the consequent need for practical, field-based monitoring strategies. Nonetheless, laboratory-based assessments remain more prevalent overall, covering the majority of hamstring strength assessment publications in the 21st century, although the proportion of field-based studies has risen markedly from 7 out of 50 studies conducted between 2010–2019 to 35 out of 77 studies from 2020 onward.

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Fig 2. Publication trends in lab vs. field-based assessment methods.

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3.5.1 Isokinetic Dynamometry (IKD).

A summary of studies utilizing IKD is provided in Table 3. Across the 122 studies, IKD protocols varied in terms of mode of contraction, angular velocities, and testing parameters, including joint angles, range of motion, and body positioning. The majority of studies reported concentric force production outcomes (97/122), followed by eccentric (53/122), and isometric (15/122). Angular velocities varied widely between studies. The most commonly assessed velocity was 60°/s (100 studies), followed by 180°/s (46 studies), 240°/s (28 studies), and 300°/s (20 studies). Other velocities utilized included 120°/s (14 studies), 30°/s (11 studies), 90°/s (6 studies), 150°/s (2 studies), and 450°/s (1 study). Intriguingly, 63 out of the 122 included studies reported evaluating hamstring-to-quadriceps (H:Q) strength ratios, highlighting a potential advantage of IKD over field-based assessment methods (e.g., force platforms or other field-based methods) which may not allow for similarly standardized protocols to examine these ratios.

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Table 3. Summary of isokinetic dynamometry (IKD) study characteristics.

https://doi.org/10.1371/journal.pone.0352509.t003

3.5.2 Force Platforms (FP).

A summary of FP studies is provided in Table 4. Across the 16 included studies, all assessments were conducted isometrically, though protocols varied in body positioning, joint angles, and limb involvement. Assessments were most commonly conducted in supine, followed by standing and prone positions, with both unilateral and bilateral testing reported. Knee joint angles varied but were most commonly set at 30° of knee flexion, followed by 90° and 20°, with hip positioning ranging from 90° to 150°.

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Table 4. Summary of force platform (FP) study characteristics.

https://doi.org/10.1371/journal.pone.0352509.t004

Similar to IKD, fewer than half of FP studies reported rapid force production metrics such as rate of force development (RFD) or force at specific time points. Only six studies included such measures, with variation in reporting across time windows (e.g., 50–100 ms, 100–150 ms) and averaged intervals. Sampling frequency also varied; 11 of 16 studies employed 1000 Hz, with others using 500, 160, 100, and 80 Hz; the implications of which are discussed further in the reliability section. Nonetheless, a clear advantage of FPs is their capacity to capture rapid force production with high validity, complementing IKD by providing an alternative means of assessing these characteristics in applied sporting environments.

Encouragingly, all FP studies reported or discussed measurement reliability, including within- and between-session estimates, with four additionally evaluating the reliability of rapid force metrics. All researchers reported 95% CIs alongside relative reliability (ICC), though only one study each for within- and between-session measurements reported CIs for absolute reliability metrics, including CV%, SEM, and MDD.

3.5.3 Nordic Hamstring Exercise (NHE).

A summary of the studies performing the NHE can be found in Table 5. Of the fifteen studies reviewed, ten utilized the NordBord, making it the most implemented assessment tool, and two studies employed the Nordic Hamstring Solo Elite, serving as an alternative approach to evaluating eccentric hamstring strength to the NordBord assessment. Most intriguingly, three studies employed the NHE Break-Point Test, which requires only a video recording device (i.e., smartphone) to capture the point of task failure, thereby providing an indirect measure of eccentric hamstring strength without the need for specialized equipment, a potentially substantial benefit for low-budget environments without access to conventional equipment. Moreover, this assessment has been successfully validated against eccentric hamstring strength measured via isokinetic dynamometry [80,81], the current gold standard [211]. According to the reviewed studies, the reported sampling frequencies were limited. Six studies explicitly reported values, with the NordBord assessments using 50 Hz (n = 4), the Hamstring Solo Elite using 5 Hz (n = 1), and the customized load cell set-up using 10 Hz. Among the remaining studies, five were assumed to use 50 Hz and one 5 Hz based on device specifications, while the three video-based break-point assessments had sampling frequencies dictated by the recording device, with one at 300 Hz, one at 60 Hz, and one unspecified.

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Table 5. Summary of instrumented Nordic hamstring exercise (NHE) device study characteristics.

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No researchers reported rapid force generation; instead focusing on peak force or average force during the NHE. Considering the NHE is performed as a slow, controlled eccentric action, this is unsurprising, as the assessment may inherently emphasize sustained over rapid force production. Nevertheless, this highlights one potential limitation of the NHE for applied monitoring purposes, particularly if rapid force capabilities are of interest.

3.5.4 Remaining assessment devices

The remaining assessments, which did not fit the primary categories above, are summarized in Table 6.

3.6 Reliability of hamstring strength characteristics

Across the included studies that reported on reliability characteristics, the reliability of hamstring strength or force-related measures was generally acceptable-moderate when assessed both via relative (intraclass correlation coefficients) and absolute reliability (coefficient of variation) measures, with few studies reporting poor reliability. In general, absolute reliability metrics, including the coefficient of variation (CV%), standard error of measurement (SEM), and minimal detectable difference (MDD), were reported less frequently. Summaries of the reliability outcomes are provided in Table 7 (within-session reliability) and Table 8 (between-session reliability).

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Table 7. Within-session reliability characteristics of assessment methods.

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Table 8. Between-session reliability of assessment methods.

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3.6.1 Isokinetic Dynamometry (IKD) reliability.

Studies employing IKD predominantly measured peak torque under eccentric or concentric contractions, with no studies reporting the reliability for isometric measures. Overall, concentric peak torque measures showed higher reliability than eccentric measures, which were somewhat more variable. Absolute reliability indices were reported only in a few studies, which suggested good-excellent reliability both between the concentric and eccentric measures. Both within- and between-session reliability can generally be considered acceptable; however, given that a few select studies that reported lower point-estimates did not include confidence intervals, direct interpretation is challenging. Nonetheless, multiple studies reveal good-to-moderate reliability measures.

3.6.2 Force Platform (FP) reliability.

Force platform-based assessments of isometric peak force demonstrated generally good to excellent within-session reliability and moderate-good between-session reliability, although one study revealed poor reliability. Measures of rapid force (100–200 ms) and rate of force development (RFD) were generally less reliable than maximal force outputs, in a descending manner. Intriguingly, however, these rapid force-time points appear to demonstrate greater reliability at lower sampling frequencies [135] and may therefore be improved depending on the methods of assessment employed. Reliability across the 90:90 and 30:30 assessment modes appears broadly similar, although the 90:20 assessments demonstrate moderate reductions in reliability compared to the other assessments, but still at an acceptable level.

3.6.3 Nordic Hamstring Exercise (NHE) reliability.

For eccentric hamstring strength, studies using the Nordbord generally demonstrated moderate to excellent relative and absolute reliability, whereas assessments using the break point angle showed slightly lower, although still acceptable, reliability. Additionally, the hamstring solo elite has also been reported to produce acceptable reliability, suggesting that alternate devices can provide comparable assessment reliability. Importantly, the NHE, similar to the majority of IKD studies, reported only one variable at an individual time point, i.e., peak force (or point at failure).

3.7 Time-course meta-analysis of hamstring strength loss following exercise or competition

3.7.1 Immediately post-intervention.

Meta-analytic results are presented separately for each time-course subgroup (Figs 3–6). For the immediate post-intervention subgroup, 11 studies (n = 186 participants) contributed to the meta-analysis, yielding a pooled effect size of −0.66 (95% CI [−0.88, −0.44]; 95% PI [−1.10, −0.22]), indicating a small-moderate decrement in hamstring strength immediately following on-field activity (see Fig 3). Overall heterogeneity was low (I² = 18.0%, τ² = 0.03, p = 0.27), suggesting effect sizes were largely consistent between studies. The eccentric subgroup (k = 5) also showed a significant, moderate pooled effect of −0.62 (95% CI [−0.90, −0.34]; 95% PI [−1.02, −0.22]) with negligible heterogeneity (I² = 0%, τ² = 0, p = 0.84). Similarly, the isometric subgroup (k = 5) also demonstrated a significant, moderate effect of −0.70 (95% CI [−1.16, −0.23]; 95% PI [−1.96, 0.57]), though with moderate heterogeneity (I² = 54.2%, τ² = 0.15, p = 0.07). The concentric subgroup only included one study and was therefore not analyzed independently. Subgroup comparison indicated no significant differences between contraction types (χ²(2) = 0.80, p = 0.67), suggesting the magnitude of strength decrement immediately post-activity does not differ substantially by contraction modality.

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Fig 3. Immediate hamstring strength decrements following on-field fatiguing activity.

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3.7.2 24 hours post-intervention.

Meta-analytic results for the 24-hour post-intervention included 9 studies (n = 157) and yielded a pooled effect size of −0.67 (95% CI [−0.89, −0.45]; 95% PI [−1.03, −0.31]), indicating a small-moderate reduction in hamstring strength 24-hours following on-field activity (see Fig 4). Overall heterogeneity was low (I² = 6.4%, τ² = 0.01, p = 0.38), suggesting that effect sizes were largely consistent across studies. Subgroup analyses revealed differential effects across contraction types. The eccentric subgroup (k = 4 studies) demonstrated a small-moderate pooled effect of −0.44 (95% CI [−0.71, −0.17]; 95% PI [−0.88, −0.01]), with no heterogeneity (I² = 0%, τ² = 0, p = 0.91). The isometric subgroup (k = 3 studies) showed a larger effect of −0.98 (95% CI [−1.38, −0.58]; 95% PI [−1.86, −0.10]), also with negligible heterogeneity (I² = 0%, τ² = 0, p = 0.44). The concentric subgroup (k = 2 studies) revealed a larger pooled effect of −1.01 (95% CI [−1.58, −0.44]; 95% PI [−4.69, 2.67]), again with no heterogeneity (I² = 0%, τ² = 0, p = 0.96), likely due to the limited study inclusion. It should be noted, however, that with only two studies contributing to this subgroup, statistical power is likely insufficient to draw meaningful conclusions regarding concentric strength decrement at this time point, as indicated by the wide prediction interval [−4.69, 2.67]. Subgroup comparisons did however indicate a significant difference between contraction types (χ²(2) = 6.39, p = 0.04), suggesting that the magnitude of strength decrements 24 hours following on-field activity may vary by contraction type, with concentric and isometric actions showing greater reductions than eccentric actions.

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Fig 4. Hamstring strength decrements 24 hours following on-field fatiguing activity.

https://doi.org/10.1371/journal.pone.0352509.g004

3.7.3 48 hours post-intervention.

Meta-analytic results for the 48-hour post-intervention included 11 studies (n = 181) and yielded a pooled effect size of −0.52 (95% CI [−0.74, −0.29]; 95% PI [−0.90, −0.13]), indicating a small-moderate reduction in hamstring strength persists up to 48 hours following on-field activity (see Fig 5). Overall heterogeneity was negligible (I² = 0.0%, τ² = 0.016, p = 0.46), suggesting that effect sizes were highly consistent across studies. Subgroup analyses by contraction mode revealed comparable effects across all modalities. The eccentric subgroup (k = 3 studies) demonstrated a pooled effect of −0.49 (95% CI [−0.89, −0.09]; 95% PI [−1.37, 0.40]), with no heterogeneity (I² = 0%, τ² = 0, p = 0.39). The isometric subgroup (k = 6 studies) showed a similar effect of −0.50 (95% CI [−0.85, −0.15]; 95% PI [−1.31, 0.31]), with moderate heterogeneity (I² = 33.8%, τ² = 0.07, p = 0.18). The concentric subgroup (k = 2 studies) yielded a pooled effect of −0.64 (95% CI [−1.19, −0.10]; 95% PI [−4.19, 2.91]), with no heterogeneity (I² = 0%, τ² = 0, p = 0.84). Though similar to the 24-hour subgroup, with only two studies contributing, statistical power is likely insufficient. Subgroup comparisons revealed no significant differences between contraction modes (χ²(2) = 0.23, p = 0.89), suggesting that hamstring strength decrements at 48 hours following on-field activity remain evident regardless of contraction mode.

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Fig 5. Hamstring strength decrements 48 hours following on-field fatiguing activity.

https://doi.org/10.1371/journal.pone.0352509.g005

3.7.4 72 hours post-intervention.

Meta-analytic results for the 72-hour post-intervention included 8 studies (n = 145) and yielded a pooled effect size of −0.40 (95% CI [−0.63, −0.16]; 95% PI [−0.68, −0.11]), indicating a small reduction in hamstring strength may persist even 72 hours following on-field activity (see Fig 6). Overall heterogeneity was once again negligible (I² = 0.0%, τ² = 0, p = 0.53), suggesting that effect sizes were consistent across studies. The eccentric subgroup only included one study and was therefore not analyzed independently. The isometric subgroup (k = 5 studies) demonstrated a pooled effect of −0.47 (95% CI [−0.80, −0.14]; 95% PI [−1.15, 0.22]), with low heterogeneity (I² = 23%, τ² = 0.03, p = 0.27). The concentric subgroup (k = 2 studies) showed a pooled effect of −0.32 (95% CI [−0.86, 0.22]; 95% PI [−3.82, 3.17]), with no heterogeneity (I² = 0%, τ² = 0, p = 0.66). Again, similar to the 24- and 48-hour subgroups, with only two studies contributing, statistical power is likely insufficient. Subgroup comparisons indicated no significant differences between contraction types (χ²(2) = 0.61, p = 0.74), suggesting that any residual hamstring strength decrements at 72 hours post on-field activity does not meaningfully differ by contraction mode.

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Fig 6. Hamstring strength decrements 72 hours following on-field fatiguing activity.

https://doi.org/10.1371/journal.pone.0352509.g006

3.7.5 Time-course strength decrement risk of publication bias.

Funnel plot assessments were conducted for each post-intervention timepoint to evaluate potential publication bias and small-study effects (see Fig 7, A-D). For the immediate post-intervention group (11 studies, Fig 7A), visual inspection revealed reasonable symmetry, supported by a non-significant Egger’s weighted regression test (t = 1.67, p = 0.129). The 24-hour timepoint (9 studies, Fig 7B) showed some visual asymmetry, with studies clustering toward the left side of the funnel, though Egger’s test remained non-significant (t = −0.90, p = 0.398). The 48-hour timepoint (11 studies, Fig 7C) demonstrated similar visual evidence of asymmetry, though it remained non-significant (t = −1.48, p = 0.172). The 72-hour timepoint (8 studies, Fig 7D) appears symmetrical with no evidence of asymmetry (t = −0.54, p = 0.611). Overall, the risk of publication bias influencing the overall meta-analytic findings appears minimal, as no significant results were found, and visual inspection revealed no significant asymmetry. However, the statistical power of these assessments is inherently limited by the number of available studies, and the results should therefore be interpreted with caution. Furthermore, considering none of the individual subgroups included 10 or more studies, formal funnel plot assessment via Egger’s test was not conducted for subgroup analyses [213].

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Fig 7. Funnel plots for hamstring strength decrements: A) immediately post-activity, B) 24 hours, C) 48 hours, D) 72 hours following on-field fatiguing activity.

https://doi.org/10.1371/journal.pone.0352509.g007

3.8 Grouped meta-analysis of inter-limb hamstring strength asymmetry

A total of 77 studies reported limb-by-limb force outputs, allowing a comparison for inter-limb strength asymmetry, with a combined sample of 3,813 participants, and a few studies reporting multiple modes of contraction, thereby resulting in 104 different force measurements available for analysis.

3.8.1 Directional inter-limb hamstring strength asymmetry.

The directional asymmetry analysis (Fig 8A) revealed an effect size of 0.16 (95% CI [0.10, 0.21]; 95% PI [−0.08, 0.39]), indicating a trivial effect on hamstring strength asymmetry across sporting populations. Overall heterogeneity was low (I² = 22.8%, τ² = 0.01, p = 0.14), suggesting effect sizes were relatively consistent between studies. Subgroup analyses revealed that inter-limb hamstring strength asymmetries were largely consistent across contraction modes. The eccentric subgroup (k = 30 measurements) demonstrated a pooled effect size of 0.14 (95% CI [0.03, 0.24]; 95% PI [−0.20, 0.47]) with moderate heterogeneity (I² = 30.5%, τ² = 0.03, p = 0.07). The isometric subgroup (k = 15 measurements) showed a similar effect of 0.27 (95% CI [0.11, 0.44]; 95% PI [−0.17, 0.72]) with moderate heterogeneity (I² = 41.2%, τ² = 0.05, p = 0.07). The concentric subgroup (k = 46 measurements) yielded a pooled effect of 0.12 (95% CI [0.06, 0.18]; 95% PI [−0.01, 0.26]) with low heterogeneity (I² = 8.6%, τ² = 0.004, p = 0.92). Subgroup comparisons indicated no significant differences between contraction modes (χ²(2) = 4.96, p = 0.084).

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Fig 8. Grouped meta-analysis of inter-limb hamstring strength differences by muscle action (concentric, isometric, eccentric): A) directional differences, B) absolute (non-directional) differences.

https://doi.org/10.1371/journal.pone.0352509.g008

3.8.2 Non-directional inter-limb hamstring strength asymmetry.

The non-directional asymmetry analysis (Fig 8B), which captures the magnitude of inter-limb strength differences regardless of which limb is stronger, yielded an overall pooled effect size of 0.21 (95% CI [0.16, 0.26]; 95% PI [0.04, 0.38]), indicating a small degree of absolute hamstring strength asymmetry. Overall heterogeneity was low (I² = 13.7%, τ² = 0.007, p = 0.88). Subgroup analyses revealed an eccentric effect size of 0.22 (95% CI [0.13, 0.31]; 95% PI [0.00, 0.44]; I² = 14.7%, τ² = 0.01, p = 0.59), an isometric effect size of 0.29 (95% CI [0.14, 0.45]; 95% PI [−0.11, 0.70]; I² = 36.3%, τ² = 0.04, p = 0.13), and a concentric effect size of 0.13 (95% CI [0.09, 0.18]; 95% PI [0.09, 0.18]; I² = 0.0%, τ² = 0.000, p = 0.99). Subgroup comparison indicated no significant differences between contraction modes (χ²(2) = 3.43, p = 0.180).

3.8.3 Practical interpretation of inter-limb hamstring strength asymmetry.

To provide clinically meaningful benchmarks for practitioners, the reported inter-limb strength differences were converted to percentage differences. The overall weighted directional asymmetry was 2.6% (SD = 4.3%), with a slight tendency toward right-limb dominance. However, this pattern is likely influenced by the predominance of soccer players in the included studies who were characterized by a right-limb dominance and potential adaptations to sport-specific demands. The non-directional analysis, which provides a more universal metric, demonstrated an overall weighted asymmetry of 3.5% (SD = 3.7%). This represents the typical magnitude of inter-limb strength differences in the cohort of samples included in this review, irrespective of limb dominance.

Collectively, these analyses suggest that inter-limb hamstring strength asymmetries in athletic populations are generally small in magnitude and largely consistent across contraction modalities, although they are evident, nonetheless.

3.8.4 Inter-limb strength asymmetry risk of publication bias.

To assess the potential risk of publication bias among studies reporting inter-limb strength differences, both visual inspection of a funnel plot (see Fig 9) and a weighted regression (Egger’s test) were performed. The funnel plot demonstrated a generally symmetrical distribution of effect sizes around the mean, which was supported by a non-significant Egger's test (t = 1.72, p = 0.088), indicating that publication bias did not substantially influence the asymmetry of the meta-analytic findings.

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Fig 9. Funnel plot of inter-limb hamstring strength differences across muscle actions (concentric, isometric, eccentric).

https://doi.org/10.1371/journal.pone.0352509.g009

3.9 Associations between hamstring strength and performance outcomes

A total of 15 studies evaluated the relationship between hamstring strength and various performance outcomes. Of these, six studies examined sprinting performance, three assessed change of direction ability, three investigated jumping performance, two explored the association between muscle mass and strength, two evaluated power outcomes during cycling tasks, one investigated the association between various anthropometric variables and strength, and one study examined the relationship between asymmetry and overall performance variables. Although these studies provide valuable insights, considerable heterogeneity exists in terms of measurement methods and assessment batteries. This variability made it inappropriate to group the outcomes together for meta-analysis. Nonetheless, the breadth of research in this area highlights a clear interest in understanding how hamstring strength influences diverse aspects of athletic performance.

4. Discussion

4.1 Methodological considerations in isokinetic dynamometry

Given that the majority of studies included in this review employed IKD while also reporting H:Q ratios, IKD-derived measures warrant dedicated consideration, especially as numerous researchers emphasized that several methodological factors must be accounted for when using IKD and interpreting its resulting values and ratios. Perhaps most notably, H:Q ratios appear more strongly determined by quadriceps than hamstring torque, with weak correlations observed between isolated hamstring torque and the ratio itself (r = 0.14–0.36) [84]. Functional H:Q ratios (eccentric flexion: concentric extension) may also be more relevant than traditional ratios (concentric flexion: concentric extension) [104], particularly regarding ACL support and anterior tibial shear forces [130]. H:Q ratios further vary with angular velocity, generally increasing at higher speeds, reflecting differential torque-velocity relationships between the two muscle groups [155], and with hip flexion angle, which may increase hamstring torque and thus alter the ratio [173]. This velocity-dependency appears practically meaningful, as H:Q ratio differences between sprinters and endurance runners are evident only at higher, but not lower contraction velocities [98], potentially reflecting sport-specific adaptations. Importantly, as with any ratio-derived value, individual components should also be examined in isolation, since the magnitude of force contributing to the ratio cannot be interpreted from the ratio alone, a limitation of particular consequence here, given that hamstring torque contributes comparatively little to the ratio’s variance relative to quadriceps torque.

Beyond peak torque, measures of rapid torque production, such as rate of torque development (RTD) or torque at velocities above 180°/s, may be able to differentiate athletes by performance level, whereas peak torques at slower velocities (e.g., 60°/s) often cannot [94,119,121,154,158]. Of particular relevance to applied practitioners, however, the ecological validity of inferring HSI risk during high-speed running from any IKD-derived measure should not be assumed, given that no IKD-based protocol approximates the angular knee extension velocities encountered during sprinting, which typically exceed 1200°/s [214], far beyond what any IKD-based protocol replicates, irrespective of the ratio type employed. Although not exclusive to IKD, practitioners should nonetheless refrain from assuming that higher isokinetic testing velocities confer greater relevance to sprint-specific conditions, given that even the highest attainable angular velocities remain substantially lower than those encountered during maximal sprinting, whilst lower velocities arguably afford a more valid assessment of maximal strength. Moreover, the validity of rapid torque production measures within IKD may be compromised by mechanical constraints of acceleration and deceleration phases [215], which may introduce inertial artefacts that confound musculoskeletal torque production [216], particularly at faster angular velocities where the available isokinetic window is considerably reduced, and which may occur at different time periods at varying velocities [217]. Collectively, whilst rapid torque production characteristics may provide more actionable and discriminating insights than maximal torque measures alone, particularly in sports requiring high-speed force production, the mechanical constraints inherent to IKD may fundamentally limit the capacity of such measures to reflect the intended neuromuscular construct, potentially explaining why only slower velocity IKD-based assessments have demonstrated associations with HSI risk [218]. Of course, such limitations do not preclude the utility of IKD within applied practice but rather necessitate that practitioners possess sufficient methodological competence to systematically control and modulate the relevant testing parameters, ensuring the construct validity of its derived measures relative to the neuromuscular qualities they are intended to reflect.

4.2 Reliability of hamstring strength assessment methods

The present systematic review and meta-analysis demonstrated that IKD, Nordic-derived, and force platform-derived assessments all exhibit good reliability for quantifying hamstring strength in athletic populations. Although IKD is typically considered the gold standard due to its proven validity, reliability, and ability to provide isolated torque measurements, its limited accessibility, time constraints, and lower ecological validity may restrict its use in applied environments, and its mechanical constraints as aforementioned may further limit the validity of certain derived measures. Fortunately, field-based devices have shown consistent and dependable performance, comparable to IKD, indicating that they offer practical and valid alternatives for monitoring hamstring strength across training and competition periods. Importantly, the growing adoption of these field-based, portable systems has enabled more frequent and accessible monitoring, allowing practitioners to identify changes in force production that may indicate early signs of neuromuscular fatigue or maladaptation. This reflects the broader movement toward integrating reliable, field-based monitoring tools into routine performance assessment and screening practices. Notably, however, SEM and MDD were not consistently reported across the primary literature (as evident in Table 8), representing an important gap in current reporting practice. Inclusion of these metrics in future studies would considerably improve the clinical interpretability of hamstring strength assessments, enabling practitioners to more confidently distinguish true changes in strength from measurement noise. Additionally, for force platform-based assessments, sampling frequency varies substantially across the included literature, which may limit the validity of early force-time metrics such as RFD, particularly over shorter epochs, though, as noted previously, evidence suggests that lower sampling frequencies may paradoxically enhance reliability for rapid force metrics [135], highlighting the importance of consistent methodological reporting in future studies.

4.3 Time-course decrement of hamstring strength following on-field activity

A consistent finding across the included studies was the decrement in hamstring strength following sport-specific, on-field activity, with deficits often remaining evident at 24, 48, and even 72 hours post competition. Such reductions in strength and performance suggest that neuromuscular recovery may be incomplete within typical inter-match intervals, as well as during return-to-field sessions that frequently occur within one to two days following competition. This period of impaired hamstring strength may therefore present an elevated window of vulnerability to HSI if appropriate recovery strategies are not employed. Importantly, across the literature, a variety of assessment approaches, including IKD, Nordic-based devices, camera-based systems, and force platforms, all appear to capture comparable strength-declines in post on-field-activity strength decrements, as reflected by the relatively similar effect sizes between studies. This similarity reinforces the practical value of these tools for routine monitoring of hamstring strength in applied sporting environments. It should be noted, however, that the evidence base across certain post-activity subgroup timepoints remains limited in terms of the number of contributing studies, most notably the concentric subgroup at 24, 48, and 72 hours following on-field activity, and findings at these intervals should therefore be regarded as preliminary and interpreted with appropriate caution until corroborated by a larger body of primary research, whilst the broader global estimates remain robust. Furthermore, perhaps most important for high-performance support staff, several interventions demonstrated measurable effects on mitigating post on-field-activity strength reductions. Specifically, for medical staff, the application of cold-water immersion (CWI) immediately after the cessation of activity was associated with accelerated recovery and faster returns to baseline strength [181], while for nutrition staff, increased protein intake or supplementation shortly after on-field activity promoted improved restoration of hamstring strength [142]. In addition, for strength and conditioning staff, higher levels of maximal strength, as well as strength-endurance capacities, appear to attenuate or even prevent the post-competition decrements altogether [90] and may attenuate posterior chain muscle damage markers [219]. Collectively, these findings emphasize the importance of integrated high-performance support structures, encompassing a variety of disciplines, in effectively managing recovery demands, reducing injury risk, and supporting consistent weekly performance throughout congested competitive schedules. Perhaps, this also helps explain why siloed or poor communication within high-performance support teams has been associated with elevated injury risk within applied, high-performance sport [220,221]. It should be noted, however, that these intervention-based findings are preliminary in nature, and given that a comprehensive evaluation of recovery modality efficacy was beyond the scope of this review, dedicated future investigation is warranted before firm conclusions can be drawn regarding their role in HSI risk mitigation.

4.4 Inter-limb asymmetry in hamstring strength

The presence and significance of limb-to-limb differences in hamstring strength have also attracted considerable attention, reflecting ongoing interest in how inter-limb asymmetries may inform monitoring practices within both performance and rehabilitation contexts. Across the literature, a substantial number of authors have examined these limb-to-limb differences in athletic populations using a range of assessment modalities. Collectively, however, this body of work suggests that hamstring strength imbalances on a population level are generally trivial in magnitude, corresponding to an overall weighted percentage difference of approximately 3.5% and a weighted standard deviation of 3.7%. More intriguingly, limb-to-limb differences appear broadly comparable across contraction modes, though much greater variability is evident during eccentric testing conditions, with weighted deviations reflecting 3.5%, 4.9%, and 6.0% for concentric, isometric, and eccentric contractions, respectively. The greater variability observed during eccentric testing indicates that individual responses are less predictable, identifying eccentric assessments as a context in which pronounced inter-limb asymmetries are more likely. This increased variability may, in part, reflect measurement characteristics, as while most authors report similar reliability for concentric and eccentric assessments (across broad interpretation bands), a small subset of investigations noted lower reliability for eccentric measures. Such reduced reliability could amplify apparent inter-limb differences, meaning that some of the larger asymmetries observed under eccentric testing conditions may partly reflect methodological limitations rather than true disparities, or alternatively may reveal meaningful asymmetries that other assessment methods are less sensitive to detecting. Collectively, these findings indicate that while population-level asymmetries are generally minimal, meaningful inter-individual variability likely exists, and practitioners should remain cognizant that such modest magnitudes may approach the measurement error thresholds of some assessment protocols, with variable intra-individual fluctuation in asymmetry indices between sessions independently reported [222]. Population-specific benchmarks should therefore be interpreted alongside device-specific reliability indices. As such, regular monitoring of limb-to-limb differences may help practitioners identify individual athletes whose profiles deviate from typical observed ranges. Therefore, integrating complementary measures of inter-limb strength differences may provide more comprehensive and individualized insights, facilitating context-specific interpretation and more targeted decision-making at the individual level.

4.5 Limitations

Several limitations should be considered when interpreting the findings of this review. First, many of the earlier studies included in the meta-analysis of IKD did not report reliability data, which limits the interpretability of their findings and may impact the confidence in pooled estimates derived from these studies. The time-course meta-analysis was constrained by the small number of available studies and participants, limiting the precision of prediction intervals and the generalizability of these findings to future research. Additionally, the limited number of studies in these subgroup analyses precluded the use of formal publication bias assessments, such as Egger’s test. The exclusion of the term injury from the Boolean search string, whilst intentional given the acute focus of this review, may have inadvertently excluded some screening or mitigation studies reporting hamstring strength outcomes within an injury-focused context. Furthermore, asymmetry data were predominantly reported as limb-to-limb difference across the included studies, precluding retrospective application of dominant/non-dominant limb classification, which may obscure task-specific neuromuscular adaptations in sports with clear unilateral dominance. Non-directional absolute asymmetry values were additionally calculated to partially mitigate this limitation. Future studies are encouraged to report asymmetry relative to limb dominance, in addition to limb-to-limb differences to facilitate more functionally meaningful comparisons.

Whilst a notable strength of this review is the substantial participant pool included, encompassing both male and female athletes, a clear disparity exists in the distribution of sexes, with the sample predominantly male and a comparatively smaller proportion of female participants. As such, the normative strength and asymmetry benchmarks reported here may not fully generalize to female athletic populations, and practitioners are encouraged to interpret these values cautiously when applied in female contexts. Future research is encouraged to specifically examine hamstring strength reliability, post-activity strength decrements, and inter-limb asymmetry in female athletes to establish sex-specific normative values and improve the applicability of monitoring frameworks across both sexes. Furthermore, approximately half of the studies included were derived from soccer cohorts, reflecting the broader research landscape in this area. Whilst this provides a robust evidence base for soccer-specific contexts, practitioners working across other sporting environments are encouraged to interpret the pooled benchmarks with consideration of sport-specific demands, which may influence both normative asymmetry values and post-activity strength decrements.

Across the meta-analyses, it should be noted that whilst each study contributed only once within any individual subgroup, studies could contribute to multiple subgroups, which may introduce a degree of statistical dependence at the broader meta-analytic level and should be considered when interpreting findings across subgroups. Furthermore, whilst title, abstract, and full-text screening were conducted independently by two reviewers, with a third reviewer consulted in instances of conflict, data extraction was performed by a single reviewer. Whilst efforts were made to ensure accuracy throughout this process, the absence of independent dual extraction with verification represents a potential limitation which could introduce the risk of extraction error. Finally, a formal certainty of evidence assessment was not performed; the precision and uncertainty of all meta-analytic outcomes are conveyed through the reporting of confidence and prediction intervals for every pooled estimate throughout the review.

5. Future research and conclusions

5.1 Directions for future research

In the future, researchers should prioritize more comprehensive reporting of reliability characteristics across multiple time-points, including rapid force production (i.e., force at specific timepoints) or RFD, which remains largely underexplored across a variety of assessments. Researchers should also investigate whether eccentric testing conditions are uniquely capable of detecting true inter-limb asymmetries that may not be apparent under concentric or isometric assessments, or whether the greater variability observed during eccentric conditions primarily reflects measurement noise. Finally, researchers should continue to examine practical strategies to mitigate post-activity hamstring strength decrements, including research into recovery protocols to provide applied guidelines for practitioners aiming at reducing injury risk and supporting consistent performance.

5.2 Conclusions

Hamstring strength can be reliably assessed across multiple testing modalities in athletic populations, with both laboratory-based IKD and field-based devices (i.e., NordBord and force platforms) demonstrating generally good reliability. Hamstring strength decrements following on-field activity are consistent and measurable, with deficits often persisting for 24–72 hours post-competition across all assessment methods. These prolonged strength reductions highlight a potential critical window of elevated injury vulnerability during congested fixture schedules, though evidence indicates that targeted interventions, including recovery modalities, nutritional strategies, and enhanced strength development, can effectively mitigate these decrements.

Inter-limb hamstring strength asymmetries in athletic populations are generally small in magnitude (~3–4%), though individual variability exists, particularly under eccentric testing conditions. Practitioners should establish individualized baselines and monitor longitudinal trends rather than interpreting small asymmetries as inherently concerning, given that these findings demonstrate that some degree of inherent asymmetry is normal across athletic populations. It should nonetheless be noted that such magnitudes are modest and may approach or fall within the measurement error of some assessment protocols. Practitioners are therefore encouraged to interpret asymmetry values in conjunction with device-specific reliability indices, such as the coefficient of variation, standard error of measurement, and minimal detectable difference, to ensure that observed limb-to-limb differences genuinely exceed the threshold of measurement noise before clinical decisions are made.

A variety of hamstring strength assessment methods can be effectively utilized depending on practitioner resources and context, as multiple modalities have demonstrated good reliability and sensitivity to post-activity fatigue as well as comparable patterns in detecting inter-limb asymmetries. This suggests that practitioners have considerable flexibility in selecting assessment tools that best fit their operational constraints while still obtaining actionable insights.

References

  1. 1. Feeley BT, Kennelly S, Barnes RP, Muller MS, Kelly BT, Rodeo SA, et al. Epidemiology of National Football League training camp injuries from 1998 to 2007. Am J Sports Med. 2008;36(8):1597–603. pmid:18443276
  2. 2. Gabbe B, Finch C, Wajswelner H, Bennell K. Australian football: injury profile at the community level. J Sci Med Sport. 2002;5(2):149–60. pmid:12188087
  3. 3. Orchard J, Seward H. Epidemiology of injuries in the Australian Football League, seasons 1997-2000. Br J Sports Med. 2002;36(1):39–44. pmid:11867491
  4. 4. Seward H, Orchard J, Hazard H, Collinson D. Football injuries in Australia at the élite level. Med J Aust. 1993;159(5):298–301. pmid:8361423
  5. 5. Ekstrand J, Bengtsson H, Waldén M, Davison M, Khan KM, Hägglund M. Hamstring injury rates have increased during recent seasons and now constitute 24% of all injuries in men’s professional football: the UEFA Elite Club Injury Study from 2001/02 to 2021/22. Br J Sports Med. 2022;57(5):292.
  6. 6. Brooks JHM, Fuller CW, Kemp SPT, Reddin DB. Epidemiology of injuries in English professional rugby union: part 1 match injuries. Br J Sports Med. 2005;39(10):757–66. pmid:16183774
  7. 7. Opar DA, Drezner J, Shield A, Williams M, Webner D, Sennett B, et al. Acute hamstring strain injury in track-and-field athletes: A 3-year observational study at the Penn Relay Carnival. Scand J Med Sci Sports. 2014;24(4):e254-9. pmid:24330073
  8. 8. Evans K, Williams M. The effect of nordic hamstring exercise on hamstring injury in professional rugby union. Br J Sports Med. 2017;51(4):316.3-317.
  9. 9. Ripley NJ, Cuthbert M, Ross S, Comfort P, McMahon JJ. The effect of exercise compliance on risk reduction for hamstring strain injury: a systematic review and meta-analyses. Int J Environ Res Public Health. 2021;18(21):11260. pmid:34769778
  10. 10. Bourne MN, Opar DA, Williams MD, Shield AJ. Eccentric knee flexor strength and risk of hamstring injuries in rugby union: a prospective study. Am J Sports Med. 2015;43(11):2663–70. pmid:26337245
  11. 11. Timmins RG, Bourne MN, Shield AJ, Williams MD, Lorenzen C, Opar DA. Short biceps femoris fascicles and eccentric knee flexor weakness increase the risk of hamstring injury in elite football (soccer): a prospective cohort study. Br J Sports Med. 2016;50(24):1524–35. pmid:26675089
  12. 12. Sim A, Timmins RG, Ruddy JD, Shen H, Liao K, Maniar N, et al. Hamstring strain injury risk factors in Australian football change over the course of the season. Med Sci Sports Exerc. 2024;56(2):297–306. pmid:37707490
  13. 13. Schache AG, Blanch PD, Dorn TW, Brown NAT, Rosemond D, Pandy MG. Effect of running speed on lower limb joint kinetics. Med Sci Sports Exerc. 2011;43(7):1260–71. pmid:21131859
  14. 14. Alt T, Komnik I, Severin J, Nodler YT, Benker R, Knicker AJ. Swing phase mechanics of maximal velocity sprints—does isokinetic lower-limb muscle strength matter? Int J Sports Physiol Perform. 2021;16(7):974–84.
  15. 15. Timmins RG, Filopoulos D, Giannakis J, Nguyen V, Ruddy JD, Hickey JT, et al. The effect of eccentric or isometric training on strength, architecture, and sprinting across an Australian football season. Med Sci Sports Exerc. 2024;56(3):564–74. pmid:38051129
  16. 16. Green B, Bourne MN, van Dyk N, Pizzari T. Recalibrating the risk of hamstring strain injury (HSI): a 2020 systematic review and meta-analysis of risk factors for index and recurrent hamstring strain injury in sport. Br J Sports Med. 2020;54(18):1081–8. pmid:32299793
  17. 17. Duhig S, Shield AJ, Opar D, Gabbett TJ, Ferguson C, Williams M. Effect of high-speed running on hamstring strain injury risk. Br J Sports Med. 2016;50(24):1536–40. pmid:27288515
  18. 18. Ruddy JD, Pollard CW, Timmins RG, Williams MD, Shield AJ, Opar DA. Running exposure is associated with the risk of hamstring strain injury in elite Australian footballers. Br J Sports Med. 2018;52(14):919–28. pmid:27884865
  19. 19. Astrella A, Iordanov D, De Caro D, Jiménez-Reyes P, Mendiguchia J. Biceps femoris muscle-tendon strain during an entire overground sprint acceleration: a biomechanical explanation for hamstring injuries in the acceleration phase. Sports Biomech. 2025;24(6):1725–38. pmid:38739086
  20. 20. Vermeulen R, van Dyk N, Whiteley R, Chamari K, Gregson W, Lolli L, et al. Injury-inciting circumstances of sudden-onset hamstring injuries: video analyses of 63 match injuries in male professional football players in the Qatar Stars League (2013-2020). Br J Sports Med. 2024;58(20):1196–204. pmid:39242176
  21. 21. Askling CM, Tengvar M, Saartok T, Thorstensson A. Acute first-time hamstring strains during high-speed running: a longitudinal study including clinical and magnetic resonance imaging findings. Am J Sports Med. 2007;35(2):197–206. pmid:17170160
  22. 22. Connell DA, Schneider-Kolsky ME, Hoving JL, Malara F, Buchbinder R, Koulouris G, et al. Longitudinal study comparing sonographic and MRI assessments of acute and healing hamstring injuries. AJR Am J Roentgenol. 2004;183(4):975–84. pmid:15385289
  23. 23. Slavotinek JP, Verrall GM, Fon GT. Hamstring injury in athletes: using MR imaging measurements to compare extent of muscle injury with amount of time lost from competition. AJR Am J Roentgenol. 2002;179(6):1621–8. pmid:12438066
  24. 24. Ripley NJ, Comfort P, McMahon J. Comparison between short, medium, and long fields of view in estimating bicep femoris fascicle length. Muscles. 2024;3(2):153–65.
  25. 25. Andrews MH, S AP, Gurchiek RD, Pincheira PA, Chaudhari AS, Hodges PW, et al. Multiscale hamstring muscle adaptations following 9 weeks of eccentric training. J Sport Health Sci. 2025;14:100996. pmid:39461588
  26. 26. Franchi MV, Fitze DP, Raiteri BJ, Hahn D, Spörri J. Ultrasound-derived biceps femoris long head fascicle length: extrapolation pitfalls. Med Sci Sports Exerc. 2020;52(1):233–43. pmid:31403609
  27. 27. Blazevich AJ, Gill ND, Zhou S. Intra- and intermuscular variation in human quadriceps femoris architecture assessed in vivo. J Anat. 2006;209(3):289–310. pmid:16928199
  28. 28. Kellis E, Galanis N, Natsis K, Kapetanos G. Validity of architectural properties of the hamstring muscles: correlation of ultrasound findings with cadaveric dissection. J Biomech. 2009;42(15):2549–54. pmid:19646698
  29. 29. Fidel MBCC, Ramos CS, Manlapaz DG, Banwell H, Gonzalez-Suarez CB. Reliability of ultrasound assessment of hamstring morphology, quality, and stiffness among healthy adults and athletes: a systematic review. J Sport Rehabil. 2024;33(6):396–415. pmid:39032922
  30. 30. Woodbridge R, Ryan C, Burkitt J, Ye-Lee D, Cronin J. Reliability of a portable fixed dynamometer during different isometric hamstring assessments. Appl Sci. 2024;14(22):10202.
  31. 31. Ripley NJ, Barber R, Fahey JT, Comfort P. Early versus late rapid force production during single-joint isometric hamstring assessment using force plates. J Strength Cond Res. 2024.
  32. 32. Opar DA, Piatkowski T, Williams MD, Shield AJ. A novel device using the Nordic hamstring exercise to assess eccentric knee flexor strength: a reliability and retrospective injury study. J Orthop Sports Phys Ther. 2013;43(9):636–40. pmid:23886674
  33. 33. Hirose N, Tsuruike M. Differences in the electromyographic activity of the hamstring, gluteus maximus, and erector spinae muscles in a variety of kinetic changes. J Strength Cond Res. 2018;32(12):3357–63. pmid:30102684
  34. 34. Onishi H, Yagi R, Oyama M, Akasaka K, Ihashi K, Handa Y. EMG-angle relationship of the hamstring muscles during maximum knee flexion. J Electromyogr Kinesiol. 2002;12(5):399–406. pmid:12223173
  35. 35. Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ. 2021;372:n71. pmid:33782057
  36. 36. Cobley S, Baker J, Wattie N, McKenna J. Annual age-grouping and athlete development: a meta-analytical review of relative age effects in sport. Sports Med. 2009;39(3):235–56. pmid:19290678
  37. 37. Downs SH, Black N. The feasibility of creating a checklist for the assessment of the methodological quality both of randomised and non-randomised studies of health care interventions. J Epidemiol Community Health. 1998;52(6):377–84. pmid:9764259
  38. 38. Asimakidis ND, Mukandi IN, Beato M, Bishop C, Turner AN. Assessment of strength and power capacities in elite male soccer: a systematic review of test protocols used in practice and research. Sports Med. 2024;54(10):2607–44. pmid:39026085
  39. 39. Jarvis P, Turner A, Read P, Bishop C. Reactive strength index and its associations with measures of physical and sports performance: a systematic review with meta-analysis. Sports Med. 2022;52(2):301–30. pmid:34606061
  40. 40. Owen C, Till K, Weakley J, Jones B. Testing methods and physical qualities of male age grade rugby union players: a systematic review. PLoS One. 2020;15(6):e0233796. pmid:32497130
  41. 41. Silverman SR, Schertz LA, Yuen HK, Lowman JD, Bickel CS. Systematic review of the methodological quality and outcome measures utilized in exercise interventions for adults with spinal cord injury. Spinal Cord. 2012;50(10):718–27. pmid:22777488
  42. 42. Hooper P, Jutai JW, Strong G, Russell-Minda E. Age-related macular degeneration and low-vision rehabilitation: a systematic review. Can J Ophthalmol. 2008;43(2):180–7. pmid:18347620
  43. 43. Guan Y, Bredin SSD, Taunton J, Jiang Q, Wu N, Warburton DER. Association between inter-limb asymmetries in lower-limb functional performance and sport injury: a systematic review of prospective cohort studies. J Clin Med. 2022;11(2):360. pmid:35054054
  44. 44. Hopkins WG, Hawley JA, Burke LM. Design and analysis of research on sport performance enhancement. Med Sci Sports Exerc. 1999;31(3):472–85. pmid:10188754
  45. 45. Higgins JPT, Thompson SG. Quantifying heterogeneity in a meta-analysis. Stat Med. 2002;21(11):1539–58. pmid:12111919
  46. 46. Koo TK, Li MY. A guideline of selecting and reporting intraclass correlation coefficients for reliability research. J Chiropr Med. 2016;15(2):155–63. pmid:27330520
  47. 47. McKay AKA, Stellingwerff T, Smith ES, Martin DT, Mujika I, Goosey-Tolfrey VL, et al. Defining training and performance caliber: a participant classification framework. Int J Sports Physiol Perform. 2022;17(2):317–31. pmid:34965513
  48. 48. Johnstone JA, Ford PA, Hughes G, Watson T, Mitchell ACS, Garrett AT. Field based reliability and validity of the bioharness™ multivariable monitoring device. J Sports Sci Med. 2012;11(4):643–52. pmid:24150074
  49. 49. Dhahbi W, Chamari K, Chèze L, Behm DG, Chaouachi A. External responsiveness and intrasession reliability of the rope-climbing test. J Strength Cond Res. 2016;30(10):2952–8. pmid:26849786
  50. 50. Carmona G, Moreno-Simonet L, Cosio PL, Astrella A, Fernández D, Padullés X, et al. Acute changes in hamstring injury risk factors after a session of high-volume maximal sprinting speed efforts in soccer players. Sports Health. 2025;17(1):15–26. pmid:39370659
  51. 51. Capaverde V de B, Oliveira GDS, de Lima-E-Silva FX, Ribeiro-Alvares JBA, Baroni BM. Do age and body size affect the eccentric knee flexor strength measured during the Nordic hamstring exercise in male soccer players? Sports Biomech. 2024;23(11):2157–67. pmid:34882067
  52. 52. Sutherland T, Heasman J, Rogalski B, Fahey-Gilmour J, Peeling P. Post-game recovery of isometric hamstring strength in a high-risk hamstring strain injury group throughout an Australian Football League season. Sci Med Footb. 2024;8(2):138–44. pmid:36519318
  53. 53. Chang Y, Tseng W, Chiu C, Hsieh T, Chang C, Dai X, et al. The effects of a preconditioning vibration rolling warm‐up on multidirectional repeated sprinting‐induced muscle damage. Eur J Sport Sci. 2024;24(1):36–44.
  54. 54. Woolhead E, Partner R, Parsley M, Jones A. Intra-rater and Inter-rater Reliability of the KangaTech (KT360) fixed frame dynamometry system during maximal isometric strength measurements of the knee flexors. Int J Sports Phys Ther. 2024;19(11):1397–406. pmid:39502541
  55. 55. Liakou CA, Fatouros IG, Poulios A, Tsatalas T, Karampina E, Karanika P, et al. Recovery kinetics following sprint training: resisted versus unresisted sprints. Eur J Appl Physiol. 2024;124(3):881–96. pmid:37776346
  56. 56. Whyte E, O’Connor S, Tobin Jones H, McBride C, O’Flynn A, Quinn O, et al. The relationship between hamstring strength tests and sprint performance in female Gaelic footballers: a correlation and linear regression analysis. PLoS One. 2024;19(6):e0302901. pmid:38857230
  57. 57. Barber R, Fahey JT, Comfort P, Ripley NJ. Normalization of rapid force to peak force in an isometric hamstring assessment using force plates. Apunts Sports Med. 2024;59(223):100450.
  58. 58. Zayar H, Mawhinney C, Chaijenkij K. Inter-limb asymmetry in female sepak takraw players: an observational study. Symmetry. 2024;16(7):902.
  59. 59. Aceña Rodríguez Á, Vita L, Quintana R, Portaz E, Abal A, Alvarez J, et al. Neuromuscular profile in isometric force of hamstrings in professional soccer players of the AFC Champions League. Retos. 2024;60:1157–63.
  60. 60. Rasp DM, Paternoster FK, Zauser M, Kern J, Schwirtz A. The development of hamstring strength over the course of a simulated soccer match. PLoS One. 2024;19(12):e0315317. pmid:39671377
  61. 61. Donaldson B, Bezodis N, Bayne H. Relationships between coordination, strength and performance during initial sprint acceleration. J Sports Sci. 2025;43(12):1095–107. pmid:40296312
  62. 62. Doyle KP, Brinken CM, Capito CN, Karp ET, Mariani MN, Meza S, et al. The impact of vertical jump height, hamstrings flexibility and strength on maximal sprint speed in Division I track and field athletes. J Strength Cond Res. 2025;39(10):1023–7. pmid:40493661
  63. 63. Rasp DM, Paternoster FK, Hanika F, Schwirtz A. Comparison of two procedures of the 90:20 isometric posterior chain test regarding the detection of hamstring muscle fatigue in soccer. Sport Sci Health. 2025;21(4):3073–83.
  64. 64. Ripley NJ, Fahey JT, Comfort P, McMahon JJ, Jones PA, Bramah C. Normative single joint isometric hamstring strength scores from professional soccer players during preseason. The Journal of Strength & Conditioning Research. 2025:10.1519/JSC.0000000000005217.
  65. 65. Delextrat A, Sastre-Munar A, de Ste Croix M, Walsh G. A cross-sectional study comparing passive and eccentric modes of an isokinetic dynamometer to assess eccentric torque in trained athletes: methodological considerations. Eur J Sport Sci. 2025;25(2):e12248. pmid:39865469
  66. 66. Wenzel VI, Leite-Nunes TD, Soldatelli IM, Bischoff ABG, Lanferdini FJ. Morphological and mechanical symmetry of the quadriceps and hamstrings in athletes. Appl Sci. 2025;15(4):2102.
  67. 67. Miralles-Iborra A, Elvira JLL, Del Coso J, Hernández-Sánchez S, Lozano-Quijada C, Moreno-Pérez V. The Influence of a competitive football match on the knee flexion and extension rate of force development and isometric muscle strength in female football players. Apunts Sports Med. 2025;15(6):3326.
  68. 68. Gheller RG, Machado JCBP, Oliveira Franco NC, Silva JVG da, Monteiro FG, Rossato M. Assessing the magnitude and direction of asymmetry in physical tests and morphological measurements in professional female soccer athletes. J Bodyw Mov Ther. 2025;41:131–7. pmid:39663079
  69. 69. Cosio PL, Moreno-Simonet L, Fernández D, Lloret M, Padulles X, Padulles JM, et al. Football (soccer) match-derived hamstring muscles residual fatigue can be monitored using early rate of torque development. Eur J Appl Physiol. 2025;125(5):1449–61. pmid:39725689
  70. 70. Coto Martín R, Pérez Mallada N, Martínez Beltrán MJ, Cuéllar Marín L, Borrás Luján PJ, Arroyo OO, et al. Differences in strength, muscle work, and hamstring/quadriceps ratio in professional and junior elite basketball players according to sex. J Funct Morphol Kinesiol. 2025;10(2):204. pmid:40566455
  71. 71. Jenner B, Bennett H, Milanese S, Sellar J, Burgess D, Arnold J. Reliability and profiling of physical performance tests in Australian Football League Women’s (AFLW) athletes. J Sci Med Sport. 2026;29(2):195–201. pmid:41033881
  72. 72. Li Y, Guo Q, Shao J, Gan Y, Zhao Y, Zhou Y. Neuromuscular factors predicting lower limb explosive strength in male college sprinters. Front Physiol. 2025;15:1498811. pmid:39839532
  73. 73. Yılmaz AK, Akgün S, Salkılıç EK, Anıl B, Akdemir E, Aktaş B, et al. The relationship between agility and lower extremity strength in female basketball players. BMC Sports Sci Med Rehabil. 2025;17(1):198. pmid:40652279
  74. 74. Lara-Desales M, Martínez-Ruiz EA, Edmond-Buckley S, Barcala Furelos M, Lago-Fuentes C. Evaluation and analysis of strength values assessed pre and post pitch session in an MLS team during the season and after the off season. Retos. 2024;61:405–14.
  75. 75. De Freitas FH, Neto VG, Paz GA, dos Santos DT, Dantas EHM, Gonçalves MM. Correlation between lower limb asymmetry and performance in professional female soccer players. Motricidade. 2024;20(3).
  76. 76. Ma Y, Zhou Z, Jin R, Wang D, Chen C. Relationship between knee isokinetic muscle strength and countermovement jump height among elite male gymnasts. Front Sports Act Living. 2025;7:1627059. pmid:40959531
  77. 77. Vicente-Mampel J, Bautista IJ, Martín F, Maroto-Izquierdo S, Van Hooren B, Baraja-Vegas L. Effects of ankle position during the Nordic Hamstring exercise on range of motion, heel contact force and hamstring muscle activation. Sports Biomech. 2024;23(11):2359–71. pmid:35045792
  78. 78. Shirani Dastjerdi A, Esmaeili H, Sadeghi M, Bashiri B. Effect of simulated handball match-induced fatigue on isokinetic hamstring-to-quadriceps ratio and evertor-to-invertor ratio in professional players. PLoS One. 2025;20(5):e0323978. pmid:40388477
  79. 79. Ripley N, Fahey J, Comfort P. The effect of different onset thresholds on isometric hamstring force-time variables using force plates. JASS. 2025;9(1):24–39.
  80. 80. Lee JWY, Li C, Yung PSH, Chan K-M. The reliability and validity of a video-based method for assessing hamstring strength in football players. J Exerc Sci Fit. 2017;15(1):18–21. pmid:29541126
  81. 81. Sconce E, Jones P, Turner E, Comfort P, Graham-Smith P. The validity of the nordic hamstring lower for a field-based assessment of eccentric hamstring strength. J Sport Rehabil. 2015;24(1):13–20. pmid:25606859
  82. 82. Carmona G, Moreno-Simonet L, Cosio PL, Astrella A, Fernández D, Cadefau JA, et al. Hamstrings on focus: are 72 hours sufficient for recovery after a football (soccer) match? A multidisciplinary approach based on hamstring injury risk factors and histology. J Sports Sci. 2024;42(12):1130–46. pmid:39087576
  83. 83. McCall A, Nedelec M, Carling C, Le Gall F, Berthoin S, Dupont G. Reliability and sensitivity of a simple isometric posterior lower limb muscle test in professional football players. J Sports Sci. 2015;33(12):1298–304. pmid:25845799
  84. 84. Bogdanis GC, Kalapotharakos VI. Knee extension strength and hamstrings-to-quadriceps imbalances in elite soccer players. Int J Sports Med. 2016;37(2):119–24. pmid:26509377
  85. 85. Ghena D, Mayhew JL, Kurth A, Thompson CB. Prediction of isokinetic leg strength from anthropometric dimensions in male college athletes. IES. 1991;1(4):187–92.
  86. 86. Koutedakis Y, Agrawal A, Sharp NCC. Isokinetic characteristics of knee flexors and extensors in male dancers, olympic oarsmen, olympic bobsleighers, and non-athletes. J Dance Med Sci. 1998;2(2):63–7.
  87. 87. Ruas CV, Brown LE, Pinto RS. Lower-extremity side-to-side strength asymmetry of professional soccer players according to playing position. Kinesiology. 2015;47(2):188–92.
  88. 88. Watson ED, Turner AA, Heslop HL. The effect of knee position on concentric isokinetic parameters. Afr J Phys Health Educ Recreat Dance. 2013;19(3):692–702.
  89. 89. Aginsky KD, Neophytou N, Charalambous T. Isokinetic hamstring and quadriceps muscle strength profiles of elite South African football players science. Afr J Phys Health Educ Recreat Dance. 2014;20(3):1225–36.
  90. 90. Matthews MJ, Heron K, Todd S, Tomlinson A, Jones P, Delextrat A, et al. Strength and endurance training reduces the loss of eccentric hamstring torque observed after soccer specific fatigue. Phys Ther Sport. 2017;25:39–46. pmid:28364615
  91. 91. Križaj J, Rauter S, Vodičar J, Hadžić V, Šimenko J. Predictors of vertical jumping capacity in soccer players. Isokinet Exerc Sci. 2019;27(1):9–14.
  92. 92. Lima PO de P, Lima AA, Coelho ACS, Lima YL, Almeida GPL, Bezerra MA, et al. Biomechanical differences in Brazilian jiu-jitsu athletes: the role of combat style. Int J Sports Phys Ther. 2017;12(1):67–74. pmid:28217417
  93. 93. Kabaciński J, Murawa M, Fryzowicz A, Dworak LB. A comparison of isokinetic knee strength and power output ratios between female basketball and volleyball players. Hum Mov. 2018;18(3):40–5.
  94. 94. Fallon Verbruggen F, Hank M, Miřátský P, Malý T, Zahálka F. Lower limb strength and training experience in elite and sub-elite female footballers. Isokinet Exerc Sci. 2023;32(1):11–20.
  95. 95. Darrall-Jones J, Breen D, Roe G, Till K, Jones B. Between-day reliability of the Hamstring Solo device during the Nordic Hamstring Curl. J Aust Strength Cond. 2021.
  96. 96. Severo-Silveira L, Fritsch CG, Baroni BM, Marques VB, Dornelles MP. Isokinetic performance of knee flexor and extensor muscles in American football players from Brazil. Rev Bras Cineantropom Desempenho Hum. 2017;19(4):426.
  97. 97. Yilmaz E, Aydin T, Kiliç S, Toluk Ö. Bilateral knee joint isokinetic muscle strength and angle specific balance ratio in soccer players. Ger J Sports Med. 2023;74(7).
  98. 98. Appen L, Duncan PW. Strength relationship of the knee musculature: effects of gravity and sport*. J Orthop Sports Phys Ther. 1986;7(5):1–235. pmid:18802259
  99. 99. Miller JP, Catlaw K, Angelopoulas C. Effect of ankle position on knee flexor and extensor torque. Isokinet Exerc Sci. 1996;6(2):153–5.
  100. 100. Dowson MN, Nevill ME, Lakomy HK, Nevill AM, Hazeldine RJ. Modelling the relationship between isokinetic muscle strength and sprint running performance. J Sports Sci. 1998;16(3):257–65. pmid:9596360
  101. 101. Aagaard P, Beyer N, Simonsen EB, Larsson B, Magnusson SP, Kjaer M. Isokinetic muscle strength and hiking performance in elite sailors. Scand J Med Sci Sports. 1998;8(3):138–44. pmid:9659673
  102. 102. Cotte T, Ferret JM. Comparative study of two isokinetics dynamometers: CYBEX NORM vs CON-TREX. IOS Press; 2003.
    • 103. Cronin JB, Hansen KT. Strength and power predictors of sports speed. J Strength Cond Res. 2005;19(2):349–57. pmid:15903374
    • 104. Olmo J, López-Illescas A, Martín I, Jato S, Rodríguez LP. Knee flexion and extension strength and H/Q ratio in high-level track and field athletes. Isokinet Exerc Sci. 2006;14(3):279–89.
    • 105. Masuda K, Kikuhara N, Takahashi H, Yamanaka K. The relationship between muscle cross-sectional area and strength in various isokinetic movements among soccer players. J Sports Sci. 2003;21(10):851–8. pmid:14620028
    • 106. Neumayr G, Hoertnagl H, Pfister R, Koller A, Eibl G, Raas E. Physical and physiological factors associated with success in professional alpine skiing. Int J Sports Med. 2003;24(8):571–5. pmid:14598192
    • 107. Bojsen-Møller J, Larsson B, Magnusson SP, Aagaard P. Yacht type and crew-specific differences in anthropometric, aerobic capacity, and muscle strength parameters among international Olympic class sailors. J Sports Sci. 2007;25(10):1117–28. pmid:17613735
    • 108. Nunes T, Coetzee B. The contribution of isokinetic strength parameters to the performance of cricket batsmen. Isokinet Exerc Sci. 2007;15(3):233–44.
    • 109. Rannama I, Bazanov B, Baskin K, Zilmer K, Roosalu M, Port K. Isokinetic muscle strength and short term cycling power of road cyclists. JHSE. 2013;8(Proc2):19–29.
    • 110. Oliveira ASC, Barbieri FA, Gonçalves M. Flexibility, torque and kick performance in soccer: effect of dominance. Sci Sports. 2013;28(3):e67–70.
    • 111. Silva JR, Ascensão A, Marques F, Seabra A, Rebelo A, Magalhães J. Neuromuscular function, hormonal and redox status and muscle damage of professional soccer players after a high-level competitive match. Eur J Appl Physiol. 2013;113(9):2193–201. pmid:23661147
    • 112. Yanagisawa O, Wakamatsu K, Taniguchi H. Functional hip characteristics and their relationship with ball velocity in college baseball pitchers. J Sport Rehabil. 2019;28(8):854–9. pmid:30300068
    • 113. Beato M, Stiff A, Coratella G. Effects of Postactivation potentiation after an eccentric overload bout on countermovement jump and lower-limb muscle strength. J Strength Cond Res. 2021;35(7):1825–32. pmid:30615009
    • 114. Pietta-Dias C, Ruas CV, Bortoluzzi R, Radaelli R, Minozzo F, Pinto RS, et al. Knee side-to-side strength asymmetry and hamstring-to-quadriceps strength ratios in professional street skateboarding athletes. Sci Sports. 2020;35(1):55–7.
    • 115. Toskić L, Dopsaj M, Toskić D, Marković M. Isokinetic muscle power of the knee extensor and flexor muscles among differently trained people in relation to gender. Hum Mov. 2020;21(3):81–9.
    • 116. Barrera J, Figueiredo AJ, Duarte J, Field A, Sarmento H. Predictors of linear sprint performance in professional football players. Biol Sport. 2023;40(2):359–64. pmid:37077793
    • 117. Cesanelli L, Eimantas N, Iovane A, Messina G, Satkunskiene D. The role of age on neuromuscular performance decay induced by a maximal intensity sprint session in a group of competitive endurance athletes. Eur J Transl Myol. 2022;32(1):10378. pmid:35330561
    • 118. Tourny-Chollet C, Leroy D. Conventional vs. dynamic hamstring-quadriceps strength ratios: a comparison between players and sedentary subjects. Isokinet Exerc Sci. 2002;10(4):183–92.
    • 119. Sac A. Knee extensor/flexor muscle torque and jump performance in male volleyball players: effect of experience and torque-angle-velocity relationships. J Mens Health. 2021;17(4):218–25.
    • 120. Jenkins NDM, Hawkey MJ, Costa PB, Fiddler RE, Thompson BJ, Ryan ED, et al. Functional hamstrings: quadriceps ratios in elite women’s soccer players. J Sports Sci. 2013;31(6):612–7. pmid:23150930
    • 121. Bamaç B, Çolak T, Özbek A, Çolak S, Cinel Y, Yenigün Ö. Isokinetic performance in elite volleyball and basketball players. Kinesiology. 2008;40(2).
    • 122. Bettariga F, Bishop C, Martorelli L, Turner A, Lazzarini SG, Algeri C, et al. Acute effects of a fatiguing protocol on peak force and rate of force development of the hamstring muscles in soccer players. J Sci Sport Exercise. 2023;6(2):177–85.
    • 123. Badau A, Cengiz ŞŞ, Karesi H, Er B. The effect of hamstring eccentric strength and asymmetry on acceleration and vertical jump perfor-mance in professional female soccer players. Retos. 2024;57:355–61.
    • 124. Svantner R, Brünn D, Líska D, Sykora J, Pupis M. The effect of eccentric hamstring strength on the change of direction speed of professional ice hockey players. J Hum Sport Exerc. 2021;16:S353–60.
    • 125. Hammami N, Ouergui I, Zinoubi B, Ben Moussa AZ, Ben Salah FZ. Relationship between isokinetic and explosive strength among elite Tunisian taekwondo practitioners. Sci Sports. 2014;29(3):150–5.
    • 126. Theoharopoulos A, Tsitskaris G, Nikopoulou M, Tsaklis P. Knee strength of professional basketball players. J Strength Cond Res. 2000;14(4):457–63.
    • 127. Maly T, Mala L, Zahalka F, Hank M, Simkova M. Muscular strength of knee extensors and flexors and bilateral and ipsilateral ratio in elite male kickboxers. Arch Budo. 2017;13:107–16.
    • 128. Chen SQ, Wang D, Zhang Q, Shi Y, Ding HY, Li F. Relationship between isokinetic lower-limb joint strength, isometric time force characteristics, and leg-spring stiffness in recreational runners. Front Physiol. 2022;12.
    • 129. Sánchez-Migallón V, Moreno-Pérez V, López-Samanes A, Fernández-Ruiz V, Gaos S, Díaz-Maroto JB, et al. Effects of consecutive matches on isometric hamstring strength, flexibility values and neuromuscular performance in female field hockey players. a prospective, observational study. Appl Sci. 2021;11(19):8938.
    • 130. Aagaard P, Simonsen EB, Trolle M, Bangsbo J, Klausen K. Isokinetic hamstring/quadriceps strength ratio: influence from joint angular velocity, gravity correction and contraction mode. Acta Physiol Scand. 1995;154(4):421–7. pmid:7484168
    • 131. Parkin S, Nowicky AV, Rutherford OM, McGregor AH. Do oarsmen have asymmetries in the strength of their back and leg muscles? J Sports Sci. 2001;19(7):521–6. pmid:11461055
    • 132. Olmo J, Castilla N. Explosive strength-related isokinetic parameters in high-level sprinters and long-distance runners: The relative power index. Isokinet Exerc Sci. 2005;13(4):243–9.
    • 133. Twist C, Sykes D. Evidence of exercise‐induced muscle damage following a simulated rugby league match. Eur J Sport Sci. 2011;11(6):401–9.
    • 134. Duarte JP, Valente-Dos-Santos J, Coelho-E-Silva MJ, Couto P, Costa D, Martinho D, et al. Reproducibility of isokinetic strength assessment of knee muscle actions in adult athletes: torques and antagonist-agonist ratios derived at the same angle position. PLoS One. 2018;13(8):e0202261. pmid:30110385
    • 135. Ripley NJ, McMahon JJ, Comfort P. Effect of sampling frequency on a unilateral isometric hamstring strength assessment using force plates. J Sci Sport Exerc. 2024.
    • 136. Harbili S. Relationship between lower extremity isokinetic strength and anaerobic power in weightlifters, basketball and soccer players. Isokinet Exerc Sci. 2015;23(2):93–100.
    • 137. Deliceoglu G, Tortu E, Keles A, Çakar AN, Özsoy H, Atalay T. Comparison of physical and physiological profiles between elite freestyle men and women wrestlers. Eur J Hum Mov. 2023;50:103–24.
    • 138. Ali A, Williams C. Isokinetic and isometric muscle function of the knee extensors and flexors during simulated soccer activity: effect of exercise and dehydration. J Sports Sci. 2013;31(8):907–16. pmid:23256821
    • 139. Zhou Z, Chen C, Yi W, Chen X, Cui W, Wu R, et al. Relationships between isokinetic knee and shoulder peak strength with maximal punch force in boxing athletes. IES. 2023;31(3):233–40.
    • 140. Portella DL, Cossio-Bolaños MA, Hespanhol JE, de Arruda M. Fat-free mass and bone mineral content positively affect peak torque production in Brazilian soccer players. Isokinet Exerc Sci. 2014;22(4):273–8.
    • 141. Lockie RG, Schultz AB, Jeffriess MD, Callaghan SJ. The relationship between bilateral differences of knee flexor and extensor isokinetic strength and multi-directional speed. Isokinet Exerc Sci. 2012;20(3):211–9.
    • 142. Poulios A, Fatouros IG, Mohr M, Draganidis DK, Deli C, Papanikolaou K, et al. Post-game high protein intake may improve recovery of football-specific performance during a congested game fixture: results from the PRO-FOOTBALL study. Nutrients. 2018;10(4):494. pmid:29659539
    • 143. Minuti T, Cigni P, Costagli M, Cucini A, Cione E, Melotto S, et al. Reliability of a custom device used to measure isometric knee flexor and extensor strength in standing position. Life (Basel). 2023;13(2):458. pmid:36836815
    • 144. Moreira PVS, Falco C, Menegaldo LL, Goethel MF, de Paula LV, Gonçalves M. Are isokinetic leg torques and kick velocity reliable predictors of competitive level in taekwondo athletes? PLoS One. 2021;16(6):e0235582. pmid:34106936
    • 145. Dello Iacono A, Padulo J, Bešlija T, Halperin I. Barbell hip-thrust exercise: test-retest reliability and correlation with isokinetic performance. J Strength Cond Res. 2021;35(3):659–67.
    • 146. Kuno M, Fukunaga T, Hirano Y, Miyashita M. Anthropometric variables and muscle properties of Japanese female ballet dancers. Int J Sports Med. 1996;17(2):100–5. pmid:8833710
    • 147. Oberg B, Möller M, Gillquist J, Ekstrand J. Isokinetic torque levels for knee extensors and knee flexors in soccer players. Int J Sports Med. 1986;7(1):50–3. pmid:3957519
    • 148. Taaffe DR, Marcus R. The muscle strength and bone density relationship in young women: dependence on exercise status. J Sports Med Phys Fitness. 2004;44(1):98–103. pmid:15181397
    • 149. Jacobs J, Olivier B, Brandt C, Jafta G. Physical profiles of all-rounders, batters, and bowlers in sub-elite women’s cricket. J Strength Cond Res. 2024;38(6):1095–102. pmid:38781468
    • 150. Vieira A, Alex S, Martorelli A, Brown LE, Moreira R, Bottaro M. Lower-extremity isokinetic strength ratios of elite springboard and platform diving athletes. Phys Sportsmed. 2017;45(2):87–91. pmid:28294692
    • 151. Akagi R, Tohdoh Y, Takahashi H. Strength and size ratios between reciprocal muscle groups in the thigh and lower leg of male collegiate soccer players. Clin Physiol Funct Imaging. 2014;34(2):121–5. pmid:23865492
    • 152. Bernard P-L, Amato M, Degache F, Edouard P, Ramdani S, Blain H, et al. Reproducibility of the time to peak torque and the joint angle at peak torque on knee of young sportsmen on the isokinetic dynamometer. Ann Phys Rehabil Med. 2012;55(4):241–51. pmid:22475877
    • 153. Kabacinski J, Szozda PM, Mackala K, Murawa M, Rzepnicka A, Szewczyk P, et al. Relationship between isokinetic knee strength and speed, agility, and explosive power in elite soccer players. Int J Environ Res Public Health. 2022;19(2):671. pmid:35055489
    • 154. Palmer TB, Hawkey MJ, Thiele RM, Conchola EC, Adams BM, Akehi K, et al. The influence of athletic status on maximal and rapid isometric torque characteristics and postural balance performance in Division I female soccer athletes and non-athlete controls. Clin Physiol Funct Imaging. 2015;35(4):314–22. pmid:24890050
    • 155. Brígido-Fernández I, García-Muro San José F, Charneco-Salguero G, Cárdenas-Rebollo JM, Ortega-Latorre Y, Carrión-Otero O, et al. Knee isokinetic profiles and reference values of professional female soccer players. Sports (Basel). 2022;10(12):204. pmid:36548501
    • 156. González-Ravé JM, Juárez D, Rubio-Arias JA, Clemente-Suarez VJ, Martinez-Valencia MA, Abian-Vicen J. Isokinetic leg strength and power in elite handball players. J Hum Kinet. 2014;41:227–33. pmid:25114749
    • 157. Dellagrana RA, Diefenthaeler F, Carpes FP, Hernandez SG, de Campos W. Evidence for isokinetic knee torque asymmetries in male long distance-trained runners. Int J Sports Phys Ther. 2015;10(4):514–9. pmid:26346973
    • 158. Palmer TB, Akehi K. Rate of torque development as a discriminator of playing level in collegiate female soccer players. J Musculoskelet Neuronal Interact. 2022;22(3):326–35. pmid:36046988
    • 159. Kong PW, de Heer H. Anthropometric, gait and strength characteristics of Kenyan distance runners. J Sports Sci Med. 2008;7(4):499–504. pmid:24149957
    • 160. Minahan C, Newans T, Quinn K, Parsonage J, Buxton S, Bellinger P. Strong, Fast, fit, lean, and safe: a positional comparison of physical and physiological qualities within the 2020 Australian women’s rugby league team. J Strength Cond Res. 2021;35(Suppl 2):S11–9. pmid:34319942
    • 161. Alfredson H, Nordström P, Lorentzon R. Total and regional bone mass in female soccer players. Calcif Tissue Int. 1996;59(6):438–42. pmid:8939768
    • 162. Motta C, de Lira CAB, Vargas VZ, Vancini RL, Andrade MS. Profiling the isokinetic muscle strength of athletes involved in sports characterized by constantly varied functional movements performed at high intensity: a cross-sectional study. PM R. 2019;11(4):354–62. pmid:30145343
    • 163. de Lacey J, Brughelli ME, McGuigan MR, Hansen KT. Strength, speed and power characteristics of elite rugby league players. J Strength Cond Res. 2014;28(8):2372–5. pmid:24513623
    • 164. Sabater Pastor F, Besson T, Berthet M, Varesco G, Kennouche D, Dandrieux PE, et al. Elite road vs. trail runners: Comparing economy, biomechanics, strength, and power. J Strength Cond Res. 2023;37(1):181–6.
    • 165. Kim H-W, Joo C-H. Effects of cold water immersion and protein intake combined recovery after eccentric exercise on exercise performance in elite soccer players. J Exerc Rehabil. 2023;19(2):126–33. pmid:37163181
    • 166. Gür H, Akova B, Pündük Z, Küçükoğlu S. Effects of age on the reciprocal peak torque ratios during knee muscle contractions in elite soccer players. Scand J Med Sci Sports. 1999;9(2):81–7. pmid:10220841
    • 167. Donovan OO, Cheung J, Catley M, McGregor AH, Strutton PH. An investigation of leg and trunk strength and reaction times of hard-style martial arts practitioners. J Sports Sci Med. 2006;5(CSSI):5–12. pmid:24376366
    • 168. Chamari K, Chaouachi A, Hambli M, Kaouech F, Wisløff U, Castagna C. The five-jump test for distance as a field test to assess lower limb explosive power in soccer players. J Strength Cond Res. 2008;22(3):944–50. pmid:18438217
    • 169. Aagaard P, Simonsen EB, Beyer N, Larsson B, Magnusson P, Kjaer M. Isokinetic muscle strength and capacity for muscular knee joint stabilization in elite sailors. Int J Sports Med. 1997;18(7):521–5. pmid:9414075
    • 170. Anderson MA, Gieck JH, Perrin DH, Weltman A, Rutt RA, Denegar CR. The relationships among isometric, isotonic, and isokinetic concentric and eccentric quadriceps and hamstring force and three components of athletic performance. J Orthop Sports Phys Ther. 1991;14(3):114–20. pmid:18796821
    • 171. Worrell TW, Denegar CR, Armstrong SL, Perrin DH. Effect of body position on hamstring muscle group average torque. J Orthop Sports Phys Ther. 1990;11(10):449–52. pmid:18796892
    • 172. Brown SR, Brughelli M, Griffiths PC, Cronin JB. Lower-extremity isokinetic strength profiling in professional rugby league and rugby union. Int J Sports Physiol Perform. 2014;9(2):358–61. pmid:23751772
    • 173. Guex K, Gojanovic B, Millet GP. Influence of hip-flexion angle on hamstrings isokinetic activity in sprinters. J Athl Train. 2012;47(4):390–5. pmid:22889654
    • 174. Comfort P, Graham-Smith P, Matthews MJ, Bamber C. Strength and power characteristics in English elite rugby league players. J Strength Cond Res. 2011;25(5):1374–84. pmid:21116201
    • 175. García-Pastor J, Alvear-Ordenes I, Arias-Giráldez D, Reguera-García MM, Alonso-Cortés B. Comparison of the agonist/antagonist tensional balance of the knee between two isokinetic positions: a pilot study on a sample of high-level competitive soccer players. Int J Environ Res Public Health. 2022;19(9):5397. pmid:35564792
    • 176. Yapici A, Findikoglu G, Dundar U. Do isokinetic angular velocity and contraction types affect the predictors of different anaerobic power tests? J Sports Med Phys Fitness. 2016;56(4):383–91. pmid:25410575
    • 177. Ghena DR, Kurth AL, Thomas M, Mayhew J. Torque characteristics of the quadriceps and hamstring muscles during concentric and eccentric loading. J Orthop Sports Phys Ther. 1991;14(4):149–54. pmid:18784395
    • 178. Zhang Q, Léam A, Fouré A, Wong DP, Hautier CA. Relationship between explosive strength capacity of the knee muscles and deceleration performance in female professional soccer players. Front Physiol. 2021;12:723041. pmid:34707509
    • 179. Zvijac JE, Toriscelli TA, Merrick WS, Papp DF, Kiebzak GM. Isokinetic concentric quadriceps and hamstring normative data for elite collegiate American football players participating in the NFL Scouting Combine. J Strength Cond Res. 2014;28(4):875–83. pmid:23820564
    • 180. Whiteley R, Jacobsen P, Prior S, Skazalski C, Otten R, Johnson A. Correlation of isokinetic and novel hand-held dynamometry measures of knee flexion and extension strength testing. J Sci Med Sport. 2012;15(5):444–50. pmid:22424705
    • 181. Alexander J, Carling C, Rhodes D. Utilisation of performance markers to establish the effectiveness of cold-water immersion as a recovery modality in elite football. Biol Sport. 2022;39(1):19–29. pmid:35173359
    • 182. Page RM, Greig M. The cumulative and residual changes in eccentric knee flexor strength indices following soccer-specific treadmill running: Novel considerations of angle specific torque. J Sports Sci. 2020;38(16):1877–85. pmid:32508286
    • 183. Draganidis D, Chatzinikolaou A, Avloniti A, Barbero-Álvarez JC, Mohr M, Malliou P, et al. Recovery kinetics of knee flexor and extensor strength after a football match. PLoS One. 2015;10(6):e0128072. pmid:26043222
    • 184. Wu X, Zhang S, Liu Y, Zhang D, Xie B. Do knee concentric and eccentric strength and sagittal-plane knee joint biomechanics differ between jumpers and non-jumpers in landing? Hum Mov Sci. 2013;32(6):1299–309. pmid:24060223
    • 185. Chen Z, Yin M, Bishop C, Ainsworth B, Li Y. Association between lower body qualities and change-of-direction performance: a meta-analysis. Int J Sports Med. 2023;44(14):1013–33. pmid:37364608
    • 186. Fritsch CG, Dornelles MP, Oliveira GDS, Baroni BM. Poor hamstrings-to-quadriceps torque ratios in male soccer players: weak hamstrings, strong quadriceps, or both? Sports Biomech. 2023;22(7):811–21. pmid:32508266
    • 187. Śliwowski R, Marynowicz J, Jadczak Ł, Grygorowicz M, Kalinowski P, Paillard T. The relationships between knee extensors/ flexors strength and balance control in elite male soccer players. PeerJ. 2021;9:e12461. pmid:34820190
    • 188. Schaeffer M, Abbruzzese LD, Tawa Z, Schultz K, Binney J, Boyle J, et al. Inter- and intra-rater reliability of handheld dynamometry for lower extremity strength testing in pre-professional dancers. J Dance Med Sci. 2021;25(2):86–95. pmid:33781377
    • 189. Thorborg K, Bandholm T, Hölmich P. Hip- and knee-strength assessments using a hand-held dynamometer with external belt-fixation are inter-tester reliable. Knee Surg Sports Traumatol Arthrosc. 2013;21(3):550–5. pmid:22773065
    • 190. Cuthbert M, Comfort P, Ripley N, McMahon JJ, Evans M, Bishop C. Unilateral vs. bilateral hamstring strength assessments: comparing reliability and inter-limb asymmetries in female soccer players. J Sports Sci. 2021;39(13):1481–8. pmid:33522427
    • 191. Lee JWY, Cai M-J, Yung PSH, Chan K-M. Reliability, validity, and sensitivity of a novel smartphone-based eccentric hamstring strength test in professional football players. Int J Sports Physiol Perform. 2018;13(5):620–4. pmid:29283704
    • 192. Beato M, de Keijzer KL, Fleming A, Coates A, La Spina O, Coratella G, et al. Post flywheel squat vs. flywheel deadlift potentiation of lower limb isokinetic peak torques in male athletes. Sports Biomech. 2023;22(11):1514–27. pmid:33112722
    • 193. Sun K, Pan D. Analysis on the characteristics and relationships of lower limbs strength and power of sailors in different positions and levels. PLoS One. 2023;18(8):e0289273. pmid:37595004
    • 194. Ryan S, Pacecca E, Tebble J, Hocking J, Kempton T, Coutts AJ. Measurement characteristics of athlete monitoring tools in professional Australian football. Int J Sports Physiol Perform. 2019;15(4):457–63. pmid:31615972
    • 195. Greig M, Siegler JC. Soccer-specific fatigue and eccentric hamstrings muscle strength. J Athl Train. 2009;44(2):180–4. pmid:19295963
    • 196. Potteiger JA, Smith DL, Maier ML, Foster TS. Relationship between body composition, leg strength, anaerobic power, and on-ice skating performance in Division I men’s hockey athletes. J Strength Cond Res. 2010;24(7):1755–62. pmid:20543730
    • 197. Greco CC, da Silva WL, Camarda SRA, Denadai BS. Fatigue and rapid hamstring/quadriceps force capacity in professional soccer players. Clin Physiol Funct Imaging. 2013;33(1):18–23. pmid:23216761
    • 198. Śliwowski R, Grygorowicz M, Hojszyk R, Jadczak Ł. The isokinetic strength profile of elite soccer players according to playing position. PLoS One. 2017;12(7):e0182177. pmid:28759603
    • 199. Baumgart C, Kurz E, Freiwald J, Hoppe MW. Effects of hip flexion on knee extension and flexion isokinetic angle-specific torques and HQ-ratios. Sports Med Open. 2021;7(1):41. pmid:34120217
    • 200. Šimenko J, Karpljuk D, Hadžić V. Monitoring of eccentric hamstring strength and eccentric derived strength ratios in judokas from a single weight category. Int J Environ Res Public Health. 2022;19(1):604. pmid:35010858
    • 201. Lodge C, Tobin D, O’Rourke B, Thorborg K. Reliability and validity of a new eccentric hamstring strength measurement device. Arch Rehabil Res Clin Transl. 2019;2(1):100034. pmid:33543063
    • 202. Cometti G, Maffiuletti NA, Pousson M, Chatard JC, Maffulli N. Isokinetic strength and anaerobic power of elite, subelite and amateur French soccer players. Int J Sports Med. 2001;22(1):45–51. pmid:11258641
    • 203. Ripley NJ, Fahey J, Cuthbert M, McMahon JJ, Comfort P. Rapid force generation during unilateral isometric hamstring assessment: reliability and relationship to maximal force. Sports Biomech. 2025;24(11):3218–29. pmid:37942715
    • 204. Ermiş E, Yilmaz AK, Kabadayi M, Bostanci Ö, Mayda MH. Bilateral and ipsilateral peak torque of quadriceps and hamstring muscles in elite judokas. J Musculoskelet Neuronal Interact. 2019;19(3):286–93. pmid:31475935
    • 205. Wilkosz P, Kabacinski J, Mackala K, Murawa M, Ostarello J, Rzepnicka A, et al. Isokinetic and isometric assessment of the knee joint extensors and flexors of professional volleyball players. Int J Environ Res Public Health. 2021;18(13):6780. pmid:34202540
    • 206. Śliwowski R, Marynowicz J, Grygorowicz M, Wieczorek A, Jadczak Ł. Are there differences in concentric isokinetic strength performance profiles between international and non-international elite soccer players? Int J Environ Res Public Health. 2020;18(1).
    • 207. Minozzo F, Lopez P, Machado CLF, Wilhelm EN, Grazioli R, Pinto RS. Alternative assessment of knee joint muscle balance of soccer players through total work-based hamstring: quadriceps ratios. Eur J Sport Sci. 2018;18(10):1398–404.
    • 208. Matinlauri A, Alcaraz PE, Freitas TT, Mendiguchia J, Abedin-Maghanaki A, Castillo A, et al. A comparison of the isometric force fatigue-recovery profile in two posterior chain lower limb tests following simulated soccer competition. PLoS One. 2019;14(5):e0206561. pmid:31050674
    • 209. Poulis I, Chatzis S, Christopoulou K, Tsolakis C. Isokinetic strength during knee flexion and extension in elite fencers. Percept Mot Skills. 2009;108(3):949–61. pmid:19725328
    • 210. Chen C, Ali Z, Rehman Rashid MA, Samethanovna MU, Wu G, Mukhametkali S, et al. Relationship between isokinetic strength of the knee joint and countermovement jump performance in elite boxers. PeerJ. 2023;11:e16521. pmid:38077436
    • 211. Park S, Myong Y, Cho M, Cho SY, Lee WH, Oh B-M, et al. Design and validation of a wearable dynamometry system for knee extension-flexion torque measurement. Sci Rep. 2024;14(1):10428. pmid:38714762
    • 212. Comfort P, Allen M, Graham-Smith P. Kinetic comparisons during variations of the power clean. J Strength Cond Res. 2011;25(12):3269–73. pmid:22080325
    • 213. Afonso J, Ramirez-Campillo R, Clemente FM, Büttner FC, Andrade R. The perils of misinterpreting and misusing “publication bias” in meta-analyses: an education review on funnel plot-based methods. Sports Med. 2024;54(2):257–69. pmid:37684502
    • 214. Alt T, Komnik I, Ryan LJ, Clark KP. Top speed sprinting: Thigh angular motion and eccentric hamstring strength in faster vs. slower sprinters. Hum Mov Sci. 2024;98:103280. pmid:39299173
    • 215. Osternig LR. Isokinetic dynamometry: implications for muscle testing and rehabilitation. Exerc Sport Sci Rev. 1986;14:45–80. pmid:3525192
    • 216. Baltzopoulos V, Brodie DA. Isokinetic dynamometry. Applications and limitations. Sports Med. 1989;8(2):101–16. pmid:2675256
    • 217. Kannus P, Beynnon B. Peak torque occurrence in the range of motion during isokinetic extension and flexion of the knee. Int J Sports Med. 1993;14(8):422–6. pmid:8300265
    • 218. Green B, Bourne MN, Pizzari T. Isokinetic strength assessment offers limited predictive validity for detecting risk of future hamstring strain in sport: a systematic review and meta-analysis. Br J Sports Med. 2018;52(5):329–36. pmid:29187349
    • 219. Owen A, Dunlop G, Rouissi M, Chtara M, Paul D, Zouhal H, et al. The relationship between lower-limb strength and match-related muscle damage in elite level professional European soccer players. J Sports Sci. 2015;33(20):2100–5. pmid:26158195
    • 220. Ekstrand J, Lundqvist D, Davison M, D’Hooghe M, Pensgaard AM. Communication quality between the medical team and the head coach/manager is associated with injury burden and player availability in elite football clubs. Br J Sports Med. 2019;53(5):304–8. pmid:30104210
    • 221. Ekstrand J, Hägglund M, Waldén M, Gauffin H, Baudot C, Biosca P, et al. Higher level of communication between the medical staff and the performance staff is associated with a lower hamstring injury burden: a substudy on 14 teams from the UEFA Elite Club Injury Study. BMJ Open Sport Exerc Med. 2025;11(1):e002182. pmid:40041682
    • 222. Sundh AE, Ripley NJ, Lamb AJ, Cantwell CJ, Comfort P. Influence of isometric hamstring assessment modality: asymmetries across bilateral and unilateral testing procedures. J Sci Sport Exerc. 2026.