Biomechanics of fencing sport: A scoping review

Objectives The aim of our scoping review was to identify and summarize current evidence on the biomechanics of fencing to inform athlete development and injury prevention. Design Scoping review. Method Peer-reviewed research was identified from electronic databases using a structured keyword search. Details regarding experimental design, study group characteristics and measured outcomes were extracted from retrieved studies, summarized and information regrouped under themes for analysis. The methodological quality of the evidence was evaluated. Results Thirty-seven peer-reviewed studies were retrieved, the majority being observational studies conducted with experienced and elite athletes. The methodological quality of the evidence was “fair” due to the limited scope of research. Male fencers were the prevalent group studied, with the lunge and use of a foil weapon being the principal movement evaluated. Motion capture and pedabarography were the most frequently used data collection techniques. Conclusions Elite fencers exhibited sequential coordination of upper and lower limb movements with coherent patterns of muscle activation, compared to novice fencers. These elite features of neuromuscular coordination resulted in higher magnitudes of forward linear velocity of the body center of mass and weapon. Training should focus on explosive power. Sex- and equipment-specific effects could not be evaluated based on available research.


Introduction
Modern fencing emerged as a competitive sport in Europe and is now a well-recognized Olympic sport, with over 150 member federations [1].Both the sport and the culture of fencing have progressed significantly over the past decades, with an estimated 22,000 participants in the United States in 2006 [2] and 25,000 in Germany in 2008 [3].The dressing culture and fighting traditions until the 19 th century are likely to have contributed to the promotion of this combat sport [4].
Owing to its unique asymmetry in movement, fencing imposes high physiological demands in terms of neuromuscular coordination, strength and power, and the impact on the musculoskeletal system [5].As an example, for the basic 'on-guard' stance, fencers align their leading foot with their opponent's position, with the trailing foot placed at an angle to the lead foot for stability [6].To score against their opponent, fencers must thrust their weapon quickly toward their opponent, which requires an explosive extension of the trailing leg to perform a forceful forward lunge.These quick 'propulsion' and 'dodge' offense/defense movements further expose fencers to impacts, explosive forces, power absorption, and shear forces of varying magnitude, asymmetrically distributed across the body [7].
Resulted from this dynamic and repetitive movements in fencing matches, fencing injuries were quite prevalent among the athletes.In spite of the rare cases of severe trauma caused by penetration (puncture by broken blades, account for 2.7-3.2%)[2,8], most of the fencing injuries arise from overuse.In a 5-year survey by the USFA [2], 184 cases of time-loss injuries were recorded for 610 exposures with an overall 30.0% of injury rate.Approximately 52% of all reportable injuries were first or second-degree strains and sprains.Lower limb is most susceptible to injuries.The injury rates were 19.6%, 15.2%, and 13.0% respectively for the knee, thigh, and ankle.These injuries also carry a high risk of chronic morbidity, predominantly achillodynia and patellofemoral pain [9].Understanding the biomechanics and demands of a sport provides a pathway to injury prevention and safety promotion [10].An analysis of the biomechanics of a sport can also improve athletes' skills, tactics and overall performance and competitiveness.
Currently for fencing, biomechanics of performance have been investigated for different movement components of the offensive and defensive manoeuvres and using varying methodologies, which has made interpretation of findings for practice difficult.Therefore, our aim was to perform a scoping review to identify, evaluate and summarize current evidence on the biomechanics of fencing to inform athlete development and injury prevention.

Search strategy and study selection
The research was approved by The Human Subject Ethics Sub-committee of The Hong Kong Polytechnic University.The reference number is HSEARS20150814001.As electronic search of five databases was conducted (PubMed, EBSCOhost, Wiley, Web of Science and Google Scholar), using a pre-defined keyword combination (fencing AND (biomechanics OR kinematics OR kinetics OR dynamics OR movements OR performance)) to identify relevant research published in English.
Publication time was not restricted.Nighty-seven articles were identified after duplication removal and screened for eligibility.Inclusion criteria were 1) studies that addressed fencers' neuromusculoskeletal features and the biomechanics of fencing movements; 2) studies that examined the performance of fencing-specific equipment and training strategy.Studies were excluded if they 1) did not involve human subjects; 2) did not provide numeric results; 3) recruited subjects for sports other than fencing.Literature search was performed on between March 3rd to March 11th, 2016.
During the article screening, titles and abstracts of identified studies were reviewed, independently, by the first two authors to ensure that studies were experimental in nature and addressed the biomechanics of fencing.Papers for retained titles were retrieved for full review to confirm relevance to the aim of our scoping review, as well as to extract required data for analysis: experimental setting and design, characteristics of the study group, sample size, and measured outcomes.Data extraction was done independently by two authors (DWW and YW) of this study.Any inconsistency in the results was solved by group discussion involving a third author (MZ).Based on these summaries of available research evidence, three emergent themes were identified and used to organize our data for analysis: (1) intrinsic, athlete-specific, factors; (2) extrinsic factors; and (3) basic biomechanics.

Quality assessment
Quality of the recruited studies was assessed by two authors (TLC and DWW) using the tool developed by the Effective Public Health Practice Project [11].Each of following components was rated: selection bias (the likelihood that the selected subjects can represent the target population); study design (the bias resulted from allocation and the independence of exposure and outcomes); confounders (the inter-group imbalance associated with variables that influence intervention or exposure); blinding (concealment of subject allocation and outcome assessment); data collection method (the validity and reliability of outcome measurement); withdrawals and drop-outs; intervention integrity (the percentage of subjects received complete intervention and reports of unintended intervention); analysis appropriate to question (correct statistics and intention-to-treat analysis).A score of 'strong', 'moderate', and 'weak' was assigned to each study according to existing standard [11].If consensus was not reached, a third author (MZ) made the final decision.

Search results
The retrieve results are summarized in Fig 1 .We identified 548 studies, with 37 retained for analysis.Among the retained studies, 24 examined the lunge manoeuvre, which was considered to be the core component of fencing (Fig 2).Nine studies did not specify the fencing manoeuvre (Table 1).The biomechanics of the lower limbs was evaluated in 27 studies, and the biomechanics of the upper limbs in 15.The majority of studies were conducted in Europe (70.3%), with three studies conducted in the United States.Expert/elite fencing athletes were the major components of research subjects, which increases the difficulty of enlarging sample size for the recruited studies because top athletes are always rare.All three types of fencing weapons were included in these studies-foils, e ´pe ´es, and sabers.Foils were addressed in 16 studies, e ´pe ´es in 10 and sabers in 6.All studies were lab-based experiments except one performed measurements during competitions (video footage) [12].Measurements during competitions could provide valuable information of high standard game and athletes.However, the video-based analysis could not quantify fencing biomechanics as accurately as in-lab 3D motion capture technique.

Sample characteristics
Relevant characteristics of the study groups in the 37 retained studies are summarized in Table 1.Male fencers were included to a higher extent than female fencers, overall, and sex-specific effects were not typically addressed.The Body Mass Index (BMI) of fencers was generally within normal limits or slightly lower (23.85kg/m 2 in fencers VS 24.95kg/m 2 in the untrained group) because fencers were commonly taller (1.83m VS 1.69m) than the general population [13].Ethnicity, which would potentially influence anthropometry, was seldom reported, limiting the generalizability of findings.Moreover, two-thirds of the studies enrolled experienced or elite fencers, which further limits the application of findings in developing comprehensive programs for athlete development and injury prevention (in this study, fencing injury refers to those injury types associated with overuse in fencing sports).

Methodological quality
The EPHPP tool assesses many important aspects of the research quality that are critical for studies in public health and injury prevention.The tool is also commonly used by professionals of various topic areas to facilitate their decision-making based on high-quality evidence.In this study, the inter-rater reliability for EPHPP was 0.87 (Cohen's kappa coefficient), indicating a good agreement between the two reviewers.As showed in Tables 2 and 3, eleven studies (29.7%) were rated as high-quality studies (strong), eight (21.6%) were rated 'weak', and the remaining eighteen (48.7%) had 'moderate' quality.For most of the recruited studies, they were less scored due to the potential bias present in research design, confounders, and sample selection.Based on the descriptions in the paper, only five studies (13.5%) were randomized controlled trial.However, they were all classified as controlled clinical trial in EPHPP assessment because none of them clarifies the method of randomization in the text.The majority of the studies had case-control design (20 studies, 54.1%) while ten were cross-sectional studies In both sexes, the percentage of offensive action (49% -55%) was higher than for defensive action (26% -31%).The number of lunges was high compared to the number of changes in direction.

N/A Anthropometric assessment
Anthropometries There were generally no significant differences between male and female fencers in all age group in terms of anthropometric measurements.
The mean somatotype of male fencers was 3.1-2.6-3.2 as compared to 3.8-14.8-3.3 in females.Female fencers were mainly situated in the ectomorph region.
Cross-sectional area of the arms was higher in males compared to females and higher on the dominant side compared to the non-dominant side.

Timing record Timing parameters
Increased target number slightly elongated reaction time and delayed the onset of muscle activation for all fencers.However, the differences were not significant in both elite and novice groups.
For both groups, the within-subject correlation was 75% (all variables of interest), indicating inter-trial consistency of movement pattern.Movement timing High-intensity movements had a mean duration of 0.7s and accounted for 6.2% of the total bout time in elite women foil fencing.
For the 5-touch and team bouts the work: recovery ratio was 1:1, indicating an increased duration of moderate-and high-intensity movements.(Continued) (27.0%).Cross-sectional studies were assigned with 'weak' in EPHPP assessment.Some studies recruited less representative samples which had limited control on confounders regarding gender [14,15], competitiveness [16][17][18], fencing events [12,14,19], and equipment features [20,21].Measurement method/collection (e.g.EMG signal processing and motion capture technique) was considered less reliable/not fully elaborated in four studies [13,[22][23][24].Statistical analysis was not performed/not introduced in details in five studies [12,15,18,25,26].Due to the nature of fencing sports and biomechanical study, outcome assessors could not be blinded to intervention/exposure.Since subjects were generally required to give their best performance in various fencing tasks, we assumed that they were not aware of the research questions for all recruited studies.In addition to EPHPP score, the main limitation across the studies was the small sample size of study groups, with 14 studies including 10 participants.Sample size estimation, based on feasibility studies, was performed in only three studies [7,27,28].Although significance level of 0.05, using two-tailed tests, was the most prevalent cut off for statistical analysis, the cut-off was not clarified in some studies [20,22].The small size of study groups increases the risk of violating the assumption of normal distribution required for parametric statistics.Yet, normality for analysis of variance and t-tests was verified in only six studies [7,17,[27][28][29][30].Therefore, the statistical methodology of studies included in our analysis was only "fair", with none of the studies reporting the statistical power of their results.Effect size, using Cohen's dstatistic (range in included studies, 0.29-2.26)and the eta-square statistic (range in included studies, 0.09-0.59)were reported in only six studies.The reliability of measured outcomes was evaluated by computing the interclass correlation coefficient (range in included studies, (0.570-0.988) in four studies [31][32][33][34].

Measurement methods
Techniques used for measurements are summarized in Table 2. Motion capture was used in 15 studies and force platform in 10 studies respectively, with electromyography measurement used in nine studies and accelerometers in five studies.However, there was noticeable variation in equipment and signal processing/analysis used across studies, even within a specific measurement technique.As an example, both infrared-based retroreflective marker [15,17,18,29,33,[35][36][37] and electromagnetic sensor tracking systems [38] were used in motion capture analysis.In terms of the processing of electromyography data, some studies used the root

Muscle activity
In lunge + touche condition, when the signal of touche was initiated more than 300ms prior to footoff, there were no significant differences between groups.When touche was initiated within 200ms prior to foot-off or at the time of postural adjustment, speed performance and speed of focal movement were significantly higher in elite fencers.

Intrinsic, athlete-specific, factors
4.1.1Sex-specific differences.As commonly reported for other sports, sex-specific differences in the kinematics of fencing were identified [35,43,44].Specifically, females exhibited greater hip adduction, knee abduction/adduction, ankle eversion and patellofemoral contact forces of the leading leg during lunging movements [30,45].Some researchers have proposed that sex-specific differences in anthropometrics, neuromuscular functions and muscle strength may account for these differences in the kinematics of the leading leg [35,43,44].Overall, the prevalence of injury was higher in female fencers (29%-44%, averaged: 36%) than in males (22%-32%, averaged: 27%) [2].However, further evidence is required to characterize sex-specific differences based on high-quality evidence.4.1.2Anthropometry and muscle strength.The assessment of anthropometrics and strength is an important component for establishing functional profiles of fencers [46].Performance of the lunge, considered to be the core component of fencing, was evaluated using stepping time or velocity, counter-movement jump strength and dynamometric tests [28,47], with some studies evaluating the value of squat jump tests for predicting lunge performance [31,34].Despite differences in measurement, there is a consensus that greater lower limb strength and explosive power generated higher lunge velocity and quicker fencing moves [48,49].Ballistic training is therefore recommended to increase the rate of muscle force generation [50,51], or a combination of resistance and ballistic training to optimize the explosive, power and endurance requirements of fencing [51,52].Turner et al. reported that most training programs were customized to a fencer's ability, sex and age by coaches, based on their experience or anecdotal knowledge rather than on evidence.Turner et al. [53] advocated the need to develop evidence-based training protocols which would consider a fencer's biomechanics, as well as physiological and psychological factors.Continued evaluation of the predictive value of somatotypes and measures of muscle strength and power to evaluate and improve fencing performance overall, and the lunge component more specifically, using multivariate analysis should be pursued in future studies.

Asymmetry.
Fencing is clearly an asymmetric sports event based on its kinematic and kinetics [3,15,18].Intuitively, the asymmetric sports contributed to asymmetry anthropometry due to the unilateral nature of the training.Irurtia et al. and Turner et al. [26,53] showed that fencers had significantly higher handgrip strength and greater isokinetic leg strength on the dominant side than on the non-dominant side.Margonato and colleagues [23] conducted surveys on national-level fencers and discovered that they had higher muscle crosssectional area in the dominant forearm.Arm and leg asymmetries were also observed in young fencers [49] However, the effects of laterality on measures of muscle structure and performance have not been always consistently reported.Poulis et al. [48] failing to identify differences in peak knee and ankle isokinetic torques between the dominant and nondominant lower limb.It was argued that fencing movements do not necessarily induce unequal muscle growth between two sides of the lower limb.In fact, both trailing and leading legs contributed significantly to the progression of various fencing actions, especially for advance and fleche [15,24].Besides, Akpinar et al. [38] investigated the differences in movement accuracy, speed, multi-joint coordination, and handedness between fencers and non-fencers in a series of hand reaching tasks.They showed that fencers may have performance symmetry superior to non-fencers due to an underlying high skill in bilateral control, while Poulis also advocated that elite fencers have all-round development on their neuromuscular system [48].In fact, the risk of injury associated with asymmetry is recognized, such that balance or weight training is often introduced to tackle with possible asymmetry-induced injuries [54-56] [36, 57].The variation in outcome measures and training method may contribute to the inconsistency of results.Therefore, the development and role of asymmetry in fencing should be subject of future studies.

Extrinsic factors
4.2.1 Weapon.Foil, saber, and epee are the three major weapons used in fencing sports.Each weapon has its own rules and strategies.Though the basic offensive and defensive techniques are universally applicable in the three weapons, their biomechanics may differ due to the variances in blade type (e.g.length and weight), valid target (e.g.torso with and without the extremities) and scoring technique (e.g.thrusting and cutting).Both epee and foil are thrusting weapons which score only by landing their tips on the valid area, while epee is heavier (775g VS 350-500g, same in blade length: 90cm) than foil.In spite of the limited evidence from existing studies, there was a trend in the numbers present that foil fencers had slightly higher peak velocity in mass center (1.92m/s VS 1.72m/s), weapon (2.91m/s VS 2.49m/ s), and the front foot (4.56m/s VS 4.10m/s) than epee fencers during the execution of simple lunge attack [16,18,24,25,29,33,[40][41][42].Though the comparison is based on different samples, there are also signs from some performance analyses that the length of action and break was shorter in foil than in epee (5.2s VS 12.7s, 15.6s VS 18.2s) [14].Ratio of action to break was lower in foil (1:3) than in epee (1:1.0-1.4)[1,58], indicating quicker-finished bouts in foil.Saber (weight: 500g, length: 88cm in the blade) is most distinctive from the other two weapons by its 'cutting' rule.Data from research on saber biomechanics was rare, but saber was thought to have a fast tempo and a quicker burst of speed than the other two weapons [59].Length of action/break (2.5±0.6s,16.5±2.7s)and ratio of action to break (1:6.5)was the lowest in saber [14].Up to date, fencing weapons were usually studies in simple movement and controlled inlab conditions, e.g.lunge and fleche.However, in-game combat is more complex involving many extensions of the fundamental actions.Saber fencing may be even faster paced than reports.
In addition to having to bear the weight of the long weapon itself, fencers' wrist further sustains abrupt and violent loading during the series of attack and defense fencing actions.Therefore, a well-designed weapon handle is important for reducing abnormal wrist joint motion and lowering the risk of wrist injury.Three types of handles are generally used in fencing: the French, the pistol, and the Italian handle.The French and Italian handles have evolved from the classical rapier handle from the Baroque period, with the French handle slightly contoured to the curve of the hand.The pistol handle is much like that of a pistol and commonly known as the "anatomical" or "orthopaedic" grip.Use of the pistol handle is advocated as it elicits lower activation in the adductor pollicis and extensor carpi radialis muscles compared to the French and Italian handles [22].Moreover, the Visconti style pistol handle also promotes a more balanced activation of forearm muscles [21,22] which would delay muscle fatigue and improve the capacity of the wrist to resists excessive motion when external forces are applied.This protective function of the pistol handle can be enhanced by placing the handle at an angle of 18˚-21˚, which also improves hit rate and accuracy while delaying the onset of early fatigue [21].
4.2.2Footwear and the fencing piste.Fencers' feet are repeatedly exposed to large transient impact shock, especially during sudden forward thrusts, increasing the risk of lower limb injuries [60].The metal carpet piste is the main source of these high impact forces.Although different overlay materials have been used for shock absorption, Greenhalgh et al. [27] could not confirm a significant attenuation of impact magnitude for different overlays.
Fencing shoes compound this problem by providing little intrinsic shock absorption, compared to standard court shoes.Geil [20] and Sinclair et al. [7] confirmed the lower shock absorption capacity of fencing shoes compared to squash and running shoes.Geil [20] did discuss the trade-off between increased shock absorption of shoes and a slower and less reliable performance, with shock absorbing materials reducing sensory information from the floor which provides important proprioceptive input for agility and balance [61].Therefore, finding a balance between shock absorption and performance remains an issue to be resolved.

Training and conditioning.
The success of fencing was largely determined by speed and explosive strength [53].Therefore, ballistic training is recommended to increase the rate of muscle force generation [62], with most of the improvements occurring within the first 200 to 300 milliseconds of a single lunge movement [63,64].Research has shown that pure fencing training regime did not induce growth of muscle strength that overrode the progression of puberty for the adolescent fencers (compared to the inactive children: increases in arm cross sectional area: 17.1% VS 6.97%, increases in grip strength: 25.81% VS 18.07%) [51].The increases of leg muscle cross sectional area (32±7%) and body mass (16±3%) in fencers was also insignificant when the effects of body height were ruled out.The author thus recommended strength training for young fencers to complement their training routine.
Training of balance and coordination is also a fundamental element [65], By taking specific balance training, fencers demonstrated better coordination (42.36% improvement in balance score) and less body sway (7.02% less in dispersion of the center of plantar pressure) in singleleg standing tasks.When coordinating touche ´and lunge movements, elite fencers produced higher sword velocity (2.90±0.30m/sVS 2.52±0.29m/s)and body center velocity (0.41±0.20m/ s VS 0.04±0.10m/s),compared to novice fencers [36,40].In their review of training programs, Turner et al. [53] reported that most programs are customized to a fencer's ability, sex and age by coaches, based on their experience or anecdotal knowledge rather than on evidence.Turner et al. advocated the need to develop evidence-based training protocols which would consider a fencer's biomechanics, as well as physiological and psychological factors.

Biomechanics of fencing
Fencing is a highly asymmetric sport, with the armed side of the body leading movement over a substantial duration of a competitive bout, and during training.Moreover, the upper and lower extremities present distinctive motion patterns, which imposes a considerable burden on the neuromuscular system, including effects of dominance on kinematics and kinetics [66].The advance, retreat, fleche, and lunge movements, commonly used in fencing, have been evaluated using motion capture, demonstrating the greater joint motion and force output required to perform the fleche and lunge movements [31,67].
4.3.1 Posture and kinematics.In lunging, power during the propulsion phase is provided by the ankle plantarflexors and knee/hip extensors of the trailing leg, with additional contribution from the hip flexors and knee extensors of the leading leg during the subsequent flight phase [15].Contrarily in fleche, both lower limbs provided power in a cyclical sprint-like manner.During the initial phase, the trailing leg provides the thrusting power as its ankle plantarflexors and knee extensors control the velocity of flexion at the ankle and knee joints of the leading leg.Once the trailing leg passes in front of the leading leg, the thrust-absorption cycle is repeated with a reversal of the power and absorption roles of the lower limbs [15].Lower limb coordination and balance also significantly influence performance, with elite fencers generating greater hip flexion force of the leading leg at the end of a lunging movement and, hence, a higher sword velocity [16,25].Range of motion of the knee and peak hip flexion range of the trailing leg and hip flexion range of the leading leg were identified as significant predictors of lunge performance, allowing fencers to assume a low on-guard position and adjust movement of the leading leg in lunge to improve their performance [16].Though these studies of fencing performance were based on small sample size, their subjects were mostly elite fencers who can represent the significance of fencing sports.Besides, the outcomes were quite consistent in terms of phase-contributors of lunge dynamics.
Study of in-shoe pressure revealed the asymmetric characteristics of weight bearing on the foot.Trautmann, Martinelli & Rosenbaum [3] and Geil [20] evaluated the distribution of plantar pressures during three fencing movements [3].Load was predominantly placed on the heel of the leading foot and on the forefoot of the trailing foot during performance of a lunge and advance, with plantar pressure being a maximum under the hallux, bilaterally, during the retreat movement, regardless of the type of shoes worn.Steward and Kopetka [24] further reported time-to-peak angular velocity of the knee joint of the trailing leg and of the elbow of on the leading side to have a significant effect on overall lunge speed.The angle of the trailing foot relative to the lead foot also influenced lunge performance [68].Gresham-Fieg, House & Zupan [32] evaluated the effects of three different angles of rear foot placement on lunge performance, confirming that placement of the rear foot perpendicular to the alignment of the forefoot produced higher magnitudes of peak and average power and average velocity of lunging.

Joint coordination and synergy.
The proximal-to-distal coupling of upper and lower limb motion ensures an effective transfer of joint segmental angular velocity of the lower limb to the maximum linear velocity of the center of mass [69], a feature which differentiates elite from novice fencers [37].Elite fencers extended the weapon arm prior to initiating front foot movement during lunge [18].Focusing specifically on the coordination among lower limb joints, Mulloy et al. [37] identified that elite fencers exhibited greater peak horizontal sword velocity and lunge distance in comparison to novice fencers through a clearly sequential increase in angular velocity of joint extension from the hip, to the knee, to the ankle.This kinematic sequence was claimed to be the correct technique that increase fencing success in elite fencers [39].Do and Yiou has identified a 'refractory period' existing between motor tasks that had negative effects on fencing performance [42].Elite fencers were competent to inhibit the effects by closely linking 'touche' movement of the arm and 'lunge' movement of the legs in perfect timeline [41].Technical training should take into account of the specific fencing movement pattern, with emphasis on practicing different movement components in combination rather than in separate form [40].

Muscle coordination and synergy.
The proximal-to-distal sequence was also reported for muscle activation, with activation of the anterior deltoid of the armed upper limb, with extension of the armed hand, preceding the lifting of the lead foot at the initiation of lunging in expert fencers [40].In contrast, novice fencers exhibited a delayed onset of upper limb muscle activity, associated with shortened propulsion phase by the trailing leg resulting in an earlier "kick off" of the trailing leg in novice fencers [18,67].Overall, elite fencers presented more coherent muscle synergies of the upper and lower limbs, compared to novice fencers, characterized by sequential activation of shoulder/elbow extensors of the armed upper limb and hip/knee extensors of the rear lower limb, followed by activation of the forelimb during lunging, with the ability to maintain this quasi-invariant pattern of activation despite changing task requirements during a fencing bout [39,67].In contrast, muscle activation patterns for novice fencers were more variable with changing task demands imposed by their opponents, often leading to interruptions in their movement [29,33].Therefore, novice fencers may not have consolidated neuromuscular strategies for complex, multi-segmental movements [70], while elite fencers are able to finely adjust muscle activation patterns to optimize attacking (lunge) efficiency without violating the "correct" kinematic sequence of upper and lower limb motions (as the sequence mentioned in section 4.3.2:rear knee extension-front shoulder extension-front knee extension-front knee flexion) [17].

Summary and remarks
Fencing is an idiosyncratic sport, with unique patterns of asymmetrical movements and biomechanics.Although athlete-specific (intrinsic) and external factors were identified as influencing performance and, probably the risk of injury, current evidence can be considered incomplete and of "fair" quality only.However, we did identify key points that can begin to inform practice, as well as providing a direction for future research.Foremost, fencing requires explosive force and as such, evidence regarding effects of sex, anthropometry, muscle structure and neuromuscular coordination is required.Although intuitively, effects of asymmetry have been discussed and evaluated, evidence of an effect of handedness on muscle strength should be more deeply studied.Moreover, elite fencers were found to have a higher capacity for bilateral performance of hand tasks than the novice or untrained individuals.However, neuromuscular control of multi-joint movements is essential to an elite fencing performance.A unique feature of fencing is the metal carpet piste and the poor shock absorbing characteristics of the fencing shoes which increase the magnitude of impact forces and the risk of foot/ankle and knee injuries.Strategies to mitigate impact forces while optimizing performance are required.
Current evidence is limited by the narrow scope of the research and "fair" methodological quality.Foremost, due to differences in the characteristics of different weapons and, therefore, movement requirements, findings are not transferable across weapon type [14].Information available largely addresses the lunge component, which is understandable as it is the core movement component in fencing.Although a range of measures of lunge performance has been used, ranging from sword velocity to timing of target hit, the predictive value of these different measures to overall tactical performance and injury has yet to be determined.Moreover, fencing contest regularly lasts for more than an hour, during which fencers experience rapid alternation between resting and intensive activity [5].Therefore, muscle fatigue and psychophysical exhaustion would influence performance measures and increase overall risk for injury and poor performance outcomes [1].Future studies will need to evaluate effects of fatigue on fencing performance.
For future direction, current training programs mainly focus on improvement of muscle strength and power, with endurance training having received relatively less attention, despite its importance to injury prevention [71,72].Footwear design will also need to be addressed to reduce exposure to repetitive high magnitude impacts.Numerical modeling, in combination with neurophysiological measures of proprioception and muscle activation and performancebased outcomes, could assist in identifying optimal design criteria for fencing shoes by predicting internal loading across the geometrically complex anatomy of the foot and ankle [73,74].

Fig 1 .
Fig 1. Flow diagram of the search strategy and screening of identified research for inclusion.doi:10.1371/journal.pone.0171578.g001

Fig 2 .
Fig 2. Sequence of movement for lunging using a saber fencer.(A) on-guard position; (B) lifting of the lead leg; (C) forward flying phase of the lead leg and push-off with the trail leg; (D) landing of the lead foot with the armed upper limb in full extension; and (E) final lunge position.doi:10.1371/journal.pone.0171578.g002

Table 2 .
(Continued) Knee range of motion (30.7˚±10.7˚)andpeakhipflexion of the trailing leg (9.7˚±10.9˚),andpeakhipflexion of the leading leg (102.0˚±13.0˚)weresignificantpredictors of sword velocity (R 2 = 0.14-0.36,p<0.01).Muscle activityThe defensive position has no significant effects on muscle activity (p = 0.39).Activity of the adductor pollicis and the extensor carpi radialis (average value = 0.16±0.02)wassignificantlylowerwhenusing the Poistol-Viscounti in comparison to other types of handles.Cronin et al., 2003 31 Identified the strength qualities predictive of lunge performance Lunge Squat performance (Fitness Works)Squat strength and velocity The average lunge velocity was 1.62±0.21m/s(concentricvelocity),Thebestthreepredictors of lunge velocity (R 2 = 0.85, p<0.05) were time to peak squat force (0.48±0.07s), leg length (83.9 ±5.2cm), and flexibility (171.0±12.5cm).When lunge velocity was normalized by body mass, the three best predictors (R 2 = 0.87, p<0.05) were time to peak squat force, mean squat power (364.0±96.8W)andrelativesquatstrength(1.65 ±0.32kg/body mass).Displacement of the footIn lunge + touche condition, when touche was initiated (onset of anterior deltoid) before the postural adjustment of lunge (200ms prior to foot off), touche speed was comparable to that in the isolated touche condition.Muscle activityWhen touche was initiated during postural adjustment, touche speed dropped.The average touche speed was significantly lower when executed at the time of foot off (2.19±0.52m/sVS2.54±0.44m/s,p<0.01)than that in the isolated touche condition.KinematicsThe court shoes significantly reduced plantar pressure by 15.37-26.38%ascompared to the fencing shoes in all fencing movements.LungePlantar pressure (Pedar) Plantar pressure Pressures were consistently higher at the front foot.The major pressured regions are the front heel and back medial forefoot (average pressure normalized by body mass: 0.0611-0.0862N/kgÁcm 2 ).(F = 17.07, p<0.001) was identified during a lunge on the concrete-based surface (14.9±8.5g)compared with the wooden-based surface (range: 11.1-12.0g).Use of a 'piste' had no significant effect on the overall impact shock magnitude (p = 0.38-0.69).

Table 2 .
(Continued) Displacement of the footThere were no significant differences in postural velocity, speed performance, speed of focal movement, onset of anterior deltoid, and time of target hit between the elite and novice fencers in isolated touche condition.