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Open Access

Peer-reviewed

Research Article

Factors affecting chronic low back pain among high school baseball players in Japan: A pilot study

  • Hidetoshi Nakao ,

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

    h_nakao@jiu.ac.jp

    Affiliation Department of Physical Therapy, Faculty of Social Work Studies, Josai International University, Togane City, Chiba, Japan

    ⨯
  • Ryota Imai ,

    Contributed equally to this work with: Ryota Imai, Masakazu Imaoka

    Roles Data curation, Investigation, Writing – review & editing

    Affiliation School of Rehabilitation, Osaka Kawasaki Rehabilitation University, Kaizuka City, Osaka, Japan

    ⨯
  • Taro Hamada,

    Roles Project administration, Writing – review & editing

    Affiliation Department of Rehabilitation, Osaka Global Orthopedic Hospital, Joto-ku Osaka City, Osaka, Japan

    ⨯
  • Masakazu Imaoka ,

    Contributed equally to this work with: Ryota Imai, Masakazu Imaoka

    Roles Investigation, Writing – review & editing

    Affiliation School of Rehabilitation, Osaka Kawasaki Rehabilitation University, Kaizuka City, Osaka, Japan

    ⨯
  • Mitsumasa Hida,

    Roles Investigation, Writing – review & editing

    Affiliation School of Rehabilitation, Osaka Kawasaki Rehabilitation University, Kaizuka City, Osaka, Japan

    ⨯
  • Takeshi Morifuji,

    Roles Writing – original draft

    Affiliation Department of Physical Therapy, Faculty of Social Work Studies, Josai International University, Togane City, Chiba, Japan

    ⨯
  • Masashi Hashimoto

    Roles Supervision, Writing – review & editing

    Affiliation Department of Rehabilitation, Faculty of Health Sciences, Nara Gakuen University, Nara City, Nara, Japan

    ⨯

Abstract

The prevalence of chronic lower back pain (CLBP) among baseball players is high. CLBP is associated with reduced participation in practice and games. This pilot study examined the factors associated with CLBP among high school baseball players in Fukui, Japan. The participants underwent two health examinations in high school: (1) as first-grade baseball players (baseline) and (2) as second-grade baseball players (follow-up); a total of 59 players who could be followed-up a year later were included in the study. Players were divided into three groups based on whether they had no lower back pain (LBP) (n = 30), improved LBP (n = 17), or CLBP (n = 12) after 1 year of follow-up. Players were evaluated on the physical and cognitive aspects of pain. The Number Rating System, Pain Catastrophizing Scale (PCS), Tampa Scale for Kinesiophobia (TSK), Central Sensitization Inventory (CSI), body characteristics (age, height, weight, body mass index, and skeletal mass index), and a medical history questionnaire regarding spondylolysis and baseball loads were used to evaluate the players. Inventory scores were highest in the CLBP group, which indicated that this group had significant pain that affected their willingness to engage in baseball-related activities. The TSK scores in the CLBP group were worse on follow-up. High school baseball players with CLBP were more likely to have lumbar spondylolysis and kinesiophobia, which are also factors related to pain chronicity. Kinesiophobia and the presence of lumbar spondylolysis should be considered when creating an exercise program for high school baseball players with CLBP.

Citation: Nakao H, Imai R, Hamada T, Imaoka M, Hida M, Morifuji T, et al. (2023) Factors affecting chronic low back pain among high school baseball players in Japan: A pilot study. PLoS ONE 18(1): e0280453. https://doi.org/10.1371/journal.pone.0280453

Editor: Yaodong Gu, Ningbo University, CHINA

Received: August 5, 2021; Accepted: December 29, 2022; Published: January 26, 2023

Copyright: © 2023 Nakao 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: The data are available on Figshare (DOI: 10.6084/m9.figshare.20097353).

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

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

Introduction

Baseball has a large following in Japan, and lower back pain (LBP) is a significant problem among baseball players because it reduces participation time and increases the risk for disability; LBP occurs not only in adulthood but also among young athletes [1]. The LBP prevalence among young baseball players aged 12−15.5 years) ranges from 8.3−15% [2]. Furthermore, LBP affects up to 48% of Japanese college baseball players [3], and the prevalence is also high in older baseball players. Therefore, it is important to analyze the pain-related factors associated with chronic LBP (CLBP) in high school players so that appropriate measures can be implemented.

LBP can interfere with athletes’ performance and in some cases, prevent them from playing the game [4]. Several factors, such as age, gender, obesity, and inactivity, have been reported to be associated with LBP in the general population [5–7]. Obesity is the most important factor associated with CLBP and should be considered in athletes [8]. In addition, baseball players routinely experience high torsional and rotational forces on the lumbar spine during hitting and throwing. This motion during baseball can lead to back stiffness, sacroiliac joint pain, or discogenic or facet joint pain [9]. We hypothesized that examining several related factors such as pain intensity, physical composition, and baseball-related load in high school baseball players with CLBP may help implement corrective measures for improving LBP.

Chronic pain constitutes both physical and mental aspects. The mental aspects include depression, anxiety, catastrophizing, kinesiophobia, and a decline in self-efficacy [10–14]. In addition, reports have identified psychosocial factors and central sensitization as risk factors for CLBP [15, 16]. Psychosocial factors may hinder athletes from resuming the sport and affect their performance.

To the best of our knowledge, no study has examined the association of body compositions with CLBP intensity in high school baseball players. Hence, this study aimed to examine factors, such as physical composition, pain evaluation, and load related to LBP, that contribute to CLBP among high school baseball players. We also aimed to identify factors that promote and alleviate CLBP.

Materials and methods

Study design and population

This study was conducted in accordance with the Declaration of Helsinki and approved by the Osaka Kawasaki Rehabilitation University Research Ethics Review Board (approval number: OKRU-RA0003). Furthermore, written informed consent was obtained from each participant.

Baseball players from a high school in Fukui Prefecture, Japan, were included in this study. Only players who could participate in practices despite having LBP were analyzed. Players with severe physical or mental conditions that prevented participation in games or with a history of lumbar surgery or central nervous system disorders were excluded. The practice frequency of the players was 6 days a week with an average of 4–5 hours per day. Japanese high school baseball games are conducted during the off-season period between December and March, and there are no external games. The practice activities during this period are running, defensive and batting, and strength training. The number of pitching practices decreased at this time.

Players completed a health survey conducted from December 2019 to December 2021. The questionnaire evaluated pain intensity, baseball-related movement, and overall performance. Based on the answers to the questionnaire, the players were grouped into the CLBP (n = 12), improved LBP (n = 17), and no LBP (n = 30) groups. Players in the CLBP group demonstrated persistent LBP between grades 1 and 2. Players in the improved LBP group responded to the questionnaire with no LBP when implemented a year later. Furthermore, players in the no-LBP group demonstrated no pain in either survey.

Pain intensity

We used a questionnaire to measure pain intensity and its psychological impacts. Pain was defined as the maximum pain felt at a specific site and scored according to a numerical rating scale (NRS) from 0 ("no pain") to 10 ("the worst imaginable pain"). CLBP was defined as persistent pain for at least ≥12 weeks and pain intensity of cause by a visual analog scale of ≥10 mm [17].

We also administered the Pain Catastrophizing Scale (PCS) [18], the shortened Japanese version of the Tampa Scale for Kinesiophobia (TSK) [19], and the Central Sensitization Inventory (CSI) [20, 21]. The PCS comprised 13 items in three domains: rumination (five items), helplessness (five items), and magnification (three items). Each item is rated on a five-point scale from 0 ("not at all") to 4 ("all the time"). The total PCS score ranged from 0 to 52. High scores indicate greater pain catastrophizing. TSK comprised 17 questions for assessing pain-related motor kinesiophobia; however, this study used a shortened version with 11 questions. TSK is used worldwide and has been validated. The CSI was developed as a screening tool to identify and quantify patients with central sensitization (CS) related symptoms. CSI-9, a shortened version of CSI, is a nine-item symptomatological and self-reported questionnaire that assesses common health-related symptoms in individuals with central susceptibility syndrome [13, 22]. The effectiveness of CSI as an assessment tool for patients with chronic pain has been demonstrated, and the total CSI score is associated with a wide range of pain, pain intensity, disability, quality of life (QOL), and pain catastrophe [23].

Body composition

Physiological parameters were measured using bioelectrical impedance analysis (Inbody, Tokyo, Japan) at 20 and 1000 kHz frequencies. In addition, data were obtained from the participants’ electronic medical records [24]. Body mass index (BMI) was calculated by dividing body weight (kg) by the square of the player’s height (m2), whereas the appendicular skeletal muscle mass index (SMI) was derived from appendicular muscle mass (kg) divided by the square of the player’s height (m2).

Baseball-related loads and injury

We evaluated the presence of pain during baseball-related movements, such as batting, throwing, ball-catching, running, and performing barbell squats. Running in baseball means a movement involving a high load, such as a dash. We collected data on the lumbar disc herniation and/or lumbar spondylolisthesis through a thorough medical history. This data was collected using a question in a Japanese language questionnaire: “Have you ever been diagnosed with the lumbar disc herniation or lumbar spondylolysis?”

Sample size

This pilot study was conducted to estimate the sample size required to identify differences among the three groups. Using IBM SPSS version 27 (IBM Corp., Armonk, NY, USA), the study was implemented to estimate the sample size, considering the mean difference among no LBP, improved LBP, and CLBP groups of 9.4 ± 5.7, 12.8 ± 4.7, and 11.7 ± 4.7, respectively for TSK outcomes. Further, 12 participants were required per group, with a statistical power of 0.8, for comparing groups using the Kruskal−Wallis test. The validity of the sample size measurement was based on the recommendation to employ approximately 12−15 participants per group in a pilot study [25].

Statistical analysis

Data were recorded and analyzed using IBM SPSS version 27. The results are presented as means and standard deviations. The Shapiro−Wilk test was used to confirm normal distribution at each endpoint. Age and PCS scores were compared using the analysis of variance test, whereas the Kruskal−Wallis test was used to analyze the height, weight, BMI, SMI, TSK, rumination, helplessness, magnification, CSI, and NRS. Post-hoc comparisons were made using the Dunn test. Fisher’s exact test was used to analyze the lumbar disc herniation and lumbar spondylolysis, pain during baseball-related movement, and muscle function. A subgroup analysis was performed in the CLBP group to identify the factors that contributed to chronicity. A Wilcoxon signed-rank test was used to analyze pain intensity, and the McNemar test was performed for baseball-related pain (running and barbel squat) at baseline and follow-up.

Results

Fig 1 outlines the selection of study participants. A total of 69 high school baseball players were examined. Eight players who had no LBP in the first grade but showed LBP in the second grade and two players who had incomplete questionnaire data were excluded. Table 1 shows the baseball experience, position, presence or absence of LBP, and LBP period at baseline. A total 59 participants were included in this study, with a mean age and baseball experience of 15.8 and 9.5 years, respectively.

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Fig 1. Flowchart of the participants’ selection.

https://doi.org/10.1371/journal.pone.0280453.g001

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Table 1. Baseline characteristics of the participants.

https://doi.org/10.1371/journal.pone.0280453.t001

Demographic characteristics and pain evaluation among the groups

The demographic body composition and pain intensity of all three groups are summarized in Table 2. Based on the data collected during the follow-up, 12 (20.3%), 17 (28.8%), and 30 (50.8%) players had CLBP, improved LBP, and no LBP, respectively.

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Table 2. Comparison of body composition and pain intensity among the three groups.

https://doi.org/10.1371/journal.pone.0280453.t002

PCS, rumination, magnification, and CSI were significantly lower at baseline in the no LBP group than in the CLBP group. For the NRS, the mean value was lowest at 0.5 points in the no LBP group. Conversely, the improved LBP and CLBP groups scored 2.5 and 3.3 points, respectively, showing a significant difference from no LBP group. At follow-up, TSK and CSI were significantly lower in the no LBP group than in the CLBP group. For the NRS, the mean value of the CLBP group was high (3.0 points), whereas the improved LBP and no LBP groups scored 0.8 and 0.6 points, respectively. The CLBP group had a mean TSK score of 21.1 points, whereas the improved LBP and no LBP groups scored 15.4 and 15.1 points, respectively. The CLBP group had a mean CSI score of 12.9 points, whereas the improved LBP and no LBP groups scored 10.5 and 6.7 points, respectively.

The CLBP group was also significantly more likely to have a history of lumbar disc herniation and/or spondylolysis, pain on baseball-related movement, and poorer muscle function (Table 3). Pain was experienced mostly during running and barbell squats.

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Table 3. Fisher’s exact test showed significant differences among the three groups.

https://doi.org/10.1371/journal.pone.0280453.t003

Pain evaluation in the CLBP group

Table 4 shows the pain evaluation scores of the CLBP group at baseline and follow-up. No significant differences were observed in pain intensity and helplessness; however, TSK scores were significantly higher at follow-up than at baseline (p <0.05). In contrast, PCS and CSI scores, rumination, and magnification were significantly lower at follow-up than at baseline (p <0.05). Table 4 demonstrates the incidence of pain during baseball-related movement in the CLBP group. No significant differences were observed in LBP presence during running and barbell squats.

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Table 4. A prospective cohort survey of characteristics for CLBP.

https://doi.org/10.1371/journal.pone.0280453.t004

Discussion

In this study, we examined the incidence and factors associated with CLBP among high school baseball players at baseline and after 1 year. At baseline, 49.1% of the players experienced LBP, and by the follow-up date, 20.3% developed CLBP. LBP increases with age [26] and is more likely to recur in athletes; this study reports an LBP prevalence of 8.3−15% and 49.1% in young and high school baseball players, respectively [2, 3].

The CLBP group had significantly higher NRS and TSK scores at baseline. On follow-up, the TSK scores had worsened; however, the PCS and CSI scores had improved despite no change in the reported pain intensity.

A previous report examined patients with non-specific LBP for at least 6 weeks. The average TSK score in this population exceeded the cut-off value, which signified a correlation between pain intensity and the Oswestry Disability Index score [27]. Thus, kinesiophobia affected the perceived pain intensity and ability to participate in activities of daily living and sports.

The CLBP group was more likely to have lumbar spondylolysis. Lumbar spondylolysis results from stress fractures of the pars interarticularis [28] and is the reported cause of LBP in almost 50% of adolescent athletes [29]. In addition, 30% of Japanese professional baseball and soccer athletes are reported to have lumbar spondylolysis [30]. Thus, our study demonstrated that players with lumbar spondylolysis were more likely to have LBP-associated kinesiophobia, limiting their movement and making CLBP more likely.

Among the baseball-related movements, running and barbell squats were more associated with LBP in the CLBP group. When the baseline and follow-up data were compared, a small reduction in pain during running and barbell squats was observed; however, the difference was not significant. Pain during baseball-related movements has traditionally been associated with swinging and throwing motions because the movements apply high torsional and rotational forces to the lumbar spine [9, 31]. However, our study identified running and barbell squat movements as the most likely triggers for pain, particularly among players with lumbar spondylolysis. While running has not been identified as a risk factor for LBP [32], baseball players with CLBP should demonstrate more care when performing these movements.

Our study suggested that kinesiophobia is significantly related to CLBP among high school baseball players. A study by Zawandka et al. [33] demonstrated that squatting requires a greater range of knee and hip joint motion among participants with CLBP, whereas Osumi et al. [34] reported that patients with high TSK scores require more time to initiate a movement and return to the original position. Thus, kinesiophobia affects joint movement ability; therefore, continuing training with running and squats poses a risk. However, aerobic exercises such as walking [35] and strength training specific to the thoracic, lumbar, and posterior hip regions have been reported to be effective in improving CLBP [36]. Therefore, an exercise program with a controlled TSK score is recommended for atheletes with CLBP.

Our present findings suggest that higher TSK in CLBP is seen among high school baseball players with lumbar spondylolysis. Future studies should investigate the association between kinesiophobia and spondylolysis in other sports, such as racquet and contact sports, as they may also have high TSK scores and lubar spondylolysis rates in CLBP.

This study has some limitations. First, it was a pilot study that analyzed a small number of participants. Second, there is no data on the exercise load. Future studies are needed to determine the relationship between CLBP and exercise load.

Conclusions

Our study aimed to examine factors, such as physical composition, pain evaluation, and load related to LBP, that contribute to CLBP among high school baseball players. We identified kinesiophobia and lumbar spondylolysis as factors related to CLBP. Therefore, particular attention should be given to kinesiophobia during running and barbell squat training, especially in young athletes. Furthermore, the TSK score and presence of lumbar spondylolysis should be considered when creating an exercise program for high school baseball players with CLBP.

Acknowledgments

The authors are grateful to the participants involved in this study. The experiments comply with the current laws of Japan where they were performed.

References

  1. 1. Hangai M, Kaneoka K, Okubo Y, Miyakawa S, Hinotsu S, Mukai N, et al. Relationship between low back pain and competitive sports activities during youth. Am J Sports Med. 2010;38: 791–796. pmid:20051500
  2. 2. Dick R, Agel J, Marshall SW. National Collegiate Athletic Association Injury Surveillance System commentaries: introduction and methods. J Athl Train. 2007;42: 173–182. pmid:21714302
  3. 3. Tasaka S, Tashiro Y, Hotta T, Aoyama T. Examination of relation between low back pain and individual practice content of college baseball players (in Japanese). Japanese Journal of Clinical Sports Medicine. 2016;24:4–9.
  4. 4. Takemitsu M, El Rassi G, Woratanarat P, Shah SA. Low back pain in pediatric athletes with unilateral tracer uptake at the pars interarticularis on single photon emission computed tomography. Spine (Phila Pa 1976). 2006;31: 909–914. pmid:16622380
  5. 5. Auvinen JP, Tammelin TH, Taimela SP, Zitting PJ, Järvelin MR, Taanila AM, et al. Is insufficient quantity and quality of sleep a risk factor for neck, shoulder and low back pain? A longitudinal study among adolescents. Eur Spine J. 2010;19: 641–649. pmid:19936804
  6. 6. Balagué F, Troussier B, Salminen JJ. Non-specific low back pain in children and adolescents: risk factors. Eur Spine J. 1999;8: 429–438. pmid:10664299
  7. 7. Meziat Filho N, Coutinho ES, Azevedo e Silva G. Association between home posture habits and low back pain in high school adolescents. Eur Spine J. 2015;24: 425–433. pmid:25212451
  8. 8. Stevans JM, Delitto A, Khoja SS, Patterson CG, Smith CN, Schneider MJ, et al. Risk factors associated with transition from acute to chronic low back pain in US patients seeking primary care. JAMA Netw Open. 2021;4: e2037371. pmid:33591367
  9. 9. Wasser JG, Zaremski JL, Herman DC, Vincent HK. Assessment and rehabilitation of chronic low back pain in baseball: part II. Res Sports Med. 2017;25: 231–243. pmid:28128000
  10. 10. Andrew R, Derry S, Taylor RS, Straube S, Phillips CJ. The costs and consequences of adequately managed chronic non-cancer pain and chronic neuropathic pain. Pain Pract. 2014;14: 79–94. pmid:23464879
  11. 11. Larsson C, Ekvall Hansson E, Sundquist K, Jakobsson U. Kinesiophobia and its relation to pain characteristics and cognitive affective variables in older adults with chronic pain. BMC Geriatr. 2016;16: 128. pmid:27387557
  12. 12. Leadley RM, Armstrong N, Reid KJ, Allen A, Misso KV, Kleijnen J. Healthy aging in relation to chronic pain and quality of life in Europe. Pain Pract. 2014;14: 547–558. pmid:24138082
  13. 13. Meints SM, Edwards RR. Evaluating psychosocial contributions to chronic pain outcomes. Prog Neuropsychopharmacol Biol Psychiatry. 2018;87: 168–182. pmid:29408484
  14. 14. Park J, Hughes AK. Nonpharmacological approaches to the management of chronic pain in community-dwelling older adults: A review of empirical evidence. J Am Geriatr Soc. 2012;60: 555–568. pmid:22288789
  15. 15. Grachev ID, Fredrickson BE, Apkarian AV. Brain chemistry reflects dual states of pain and anxiety in chronic low back pain. J Neural Transm (Vienna). 2002;109: 1309–1334. pmid:12373563
  16. 16. Mansour AR, Farmer MA, Baliki MN, Apkarian AV. Chronic pain: The role of learning and brain plasticity. Restor Neurol Neurosci. 2014;32: 129–139. pmid:23603439
  17. 17. Dionne CE, Dunn KM, Croft PR, Nachemson AL, Buchbinder R, Walker BF, et al. A consensus approach toward the standardization of back pain definitions for use in prevalence studies. Spine (Phila Pa 1976). 2008;33: 95–103. pmid:18165754
  18. 18. Sullivan MJL, Bishop SR, Pivik J. The Pain Catastrophizing Scale: Development and validation. Psychol Assess. 1995;7: 524–532.
  19. 19. Woby SR, Roach NK, Urmston M, Watson PJ. Psychometric properties of the TSK-11: A shortened version of the Tampa Scale for Kinesiophobia. Pain. 2005;117: 137–144. pmid:16055269
  20. 20. Mayer TG, Neblett R, Cohen H, Howard KJ, Choi YH, Williams MJ, et al. The development and psychometric validation of the central sensitization inventory. Pain Pract. 2012;12: 276–285. pmid:21951710
  21. 21. Neblett R, Cohen H, Choi Y, Hartzell MM, Williams M, Mayer TG, et al. The Central Sensitization Inventory (CSI): Establishing clinically significant values for identifying central sensitivity syndromes in an outpatient chronic pain sample. J Pain. 2013;14: 438–445. pmid:23490634
  22. 22. Nishigami T, Tanaka K, Mibu A, Manfuku M, Yono S, Tanabe A. Development and psychometric properties of short form of central sensitization inventory in participants with musculoskeletal pain: A cross-sectional study. PLoS One. 2018;13: e0200152. pmid:29975754
  23. 23. van der Noord R, Paap D, van Wilgen CP. Convergent validity and clinically relevant categories for the Dutch Central Sensitization Inventory in patients with chronic pain. J Appl Biobehav Res. 2018;23: e12119.
  24. 24. Imaoka M, Nakao H, Nakamura M, Tazaki F, Maebuchi M, Ibuki M, et al. Effect of multicomponent exercise and nutrition support on the cognitive function of older adults: A randomized controlled trial. Clin Interv Aging. 2019;14: 2145–2153. pmid:31849458
  25. 25. Julious SA. Sample size of 12 per group rule of thumb for a pilot study. Pharm Stat. 2005;4: 287–291.
  26. 26. Ng L, Perich D, Burnett A, Campbell A, O’Sullivan P. Self-reported prevalence, pain intensity and risk factors of low back pain in adolescent rowers. J Sci Med Sport. 2014;17: 266–270. pmid:23994346
  27. 27. Wertli MM, Rasmussen-Barr E, Weiser S, Bachmann LM, Brunner F. The role of fear avoidance beliefs as a prognostic factor for outcome in patients with non-specific low back pain: a systematic review. Spine J. 2014;14: 816-836.e4. pmid:24412032
  28. 28. Violas P, Lucas G. L5S1 spondylolisthesis in children and adolescents. Orthop Traumatol Surg Res. 2016;102: S141–147. pmid:26774904
  29. 29. Cavalier R, Herman MJ, Cheung EV, Pizzutillo PD. Spondylolysis and spondylolisthesis in children and adolescents: I. Diagnosis, natural history, and nonsurgical management. J Am Acad Orthop Surg. 2006;14: 417–424. pmid:16822889
  30. 30. Sakai T, Sairyo K, Suzue N, Kosaka H, Yasui N. Incidence and etiology of lumbar spondylolysis: review of the literature. J Orthop Sci. 2010;15: 281–288. pmid:20559793
  31. 31. Lim YT, Chow JW, Chae WS. Lumbar spinal loads and muscle activity during a golf swing. Sports Biomech. 2012;11: 197–211. pmid:22900401
  32. 32. Maselli F, Storari L, Barbari V, Colombi A, Turolla A, Gianola S, et al. Prevalence and incidence of low back pain among runners: a systematic review. BMC Musculoskelet Disord. 2020;21: 343. pmid:32493481
  33. 33. Zawadka M, Smołka J, Skublewska-Paszkowska M, Łukasik E, Zieliński G, Byś A, et al. Altered squat movement pattern in patients with chronic low back pain. Annals of agricultural and environmental medicine: AAEM. 2021;28: 158–162. Epub 2021/03/30. pmid:33775082
  34. 34. Osumi M, Sumitani M, Otake Y, Nishigami T, Mibu A, Nishi Y, et al. Kinesiophobia modulates lumbar movements in people with chronic low back pain: a kinematic analysis of lumbar bending and returning movement. Eur Spine J. 2019;28: 1572–1578. pmid:31115684
  35. 35. Nduwimana I, Nindorera F, Thonnard JL, Kossi O. Effectiveness of walking versus mind-body therapies in chronic low back pain: A systematic review and meta-analysis of recent randomized controlled trials. Medicine. 2020;99(35):e21969. Epub 2020/09/03. pmid:32871946; PubMed Central PMCID: PMC7458239.
  36. 36. Tataryn N, Simas V, Catterall T, Furness J, Keogh JWL. Posterior-Chain Resistance Training Compared to General Exercise and Walking Programmes for the Treatment of Chronic Low Back Pain in the General Population: A Systematic Review and Meta-Analysis. Sports medicine—open. 2021;7(1):17. Epub 2021/03/09. pmid:33683497; PubMed Central PMCID: PMC7940464.