Scientific References

At Natur Athletics, we are committed to blending cutting-edge science with innovative design to deliver footwear that supports natural movement and promotes long-term foot health. To ensure our products are grounded in trusted research, we’ve carefully curated a collection of scientific studies, expert opinions, and clinical findings from renowned authors and publications in the fields of foot development, biomechanics, and injury prevention. These references have shaped our approach to creating shoes that align with the body’s natural anatomy, improve performance, and help prevent injuries. From understanding the growth trajectory of children's feet to the influence of footwear on joint stability, these scientific insights have been integral to developing our brand and ensuring that every pair of Natur Athletics cleats offers unparalleled comfort, support, and durability for young athletes and adults alike.

The Foot's Journey

“While several bones ossify prenatally, the main ossification period extends over the first ten years of life “(1)

1. Armen S. Kelikian, Shahan K. Sarrafian, Sarrafian's Anatomy of the Foot and Ankle: Descriptive, Topographic, Functional, Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2011
2. Barisch-Fritz, Bettina, Marlene Mauch, “3 - Foot Development in Childhood and Adolescence.” Essay. In Handbook of Footwear Design and Manufacture, 49–71. Oxford: Woodhead Publishing, 2013.

“The centres of ossification in the navicular emerge around the age of three years with a high variance” (3)

3. M. Walther, D. Herold, A. Sinderhauf, H. Körger, F. Kleindienst, B. Krabbe, “Requirements for children sport shoes, when taking into consideration the evolution of the child’s foot. A systematic review of current literature,” Fuß & Sprunggelenk 3 (2005): 23-33.
4. Irene S. Davis, Karsten Hollander, Daniel E. Lieberman, Sarah T. Ridge, Isabel C.N. Sacco, Scott C. Wearing, “Stepping Back to Minimal Footwear: Applications Across the Lifespan,” Exercise and Sports Science Reviews 49, no 4 (2021): 228-243.
5. Maisie Squibb, Kelly Sheerin, Peter Francis, “Measurement of the Developing Foot in Shod and Barefoot Paediatric Populations: A Narrative Review,” Children (Basel) 9, no 5 (2022):750.
6. Wieland Kinz, Elisabeth Groll-Knapp, Michael Kundi, “Hallux valgus in pre-school-aged children: the effects of too-short shoes on the hallux angle and the effects of going barefoot on podiatric health,” Footwear Science 13, no 1 (2021): 38-40.

“Epiphyseal union of all long bones in the foot, as well as the talus and calcaneus, occur throughout late adolescence or early adulthood, representing the end of foot bone growth” (7)

7. Cardoso HFV, Severino RSS, “The Chronology of Epiphyseal Union in the Hand and Foot from Dry Bone Observations,” International Journal of Osteoarchaeology 20, no 6 (2010):737-46.

“The foot typically achieves its final length at an age of about 13 years in girls and 15 years in boys” (8)

8. Anderson M, Blais M, Green WT, “Growth of the normal foot during childhood and adolescence; length of the foot and interrelations of foot, stature, and lower extremity as seen in serial records of children between 1-18 years of age,” American Journal of Physical Anthropology 14, no 2 (1956):287-308.
9. Caleb Wegener, Andrew Greene, Joshua Burns, Adrienne E. Hunt, Benedicte Vanwanseele, Richard M. Smith, “In-shoe multi-segment foot kinematics of children during the propulsive phase of walking and running,” Human Movement Science 39 (2015): 200-211.
10. “Footwear fit in schoolchildren of southern Spain: a population study” BMC Musculoskeletal Disorders 20, no 208 (2019).
11. Marise Carina Breet, Ranel Venter, “Are habitually barefoot children compelled to wear ill-fitting school shoes? A cross-sectional study,” BMC Pediatrics 22, no 187 (2022).

Ankle Stability

1. Robroy L. Martin, Todd E. Davenport, John J. Fraser, Jenna Sawdon-Bea, Christopher R. Carcia, Lindsay A. Carroll, Benjamin R. Kivlan, Dominic Carreira, “Ankle Stability and Movement Coordination Impairments: Lateral Ankle Ligament Sprains Revision,” Journal of Orthopedic and Sports Physical Therapy 51, no 4 (2021): CPG1-CPG80

Ankle sprains are most common in indoor/court sports such as volleyball and basketball, occurring at a rate of 7 ankle sprains per 1000 athlete exposures. ² Field sports, such as soccer, football, and rugby, have a much lower pooled incidence, at only 1 ankle sprain per 1000 athlete exposures. ²

The same meta-analysis found that the incidence and prevalence of ankle sprains were greatest in children 12 years of age or younger (incidence, 2.85 per 1000 exposures; 95% confidence interval [CI]: 2.51, 3.19; prevalence, 12.62% of injuries). ² Adolescents (age, 13–17 years) sustained sprains at a rate of 1.94 per 1000 exposures (95% CI: 1.73, 2.14), while adults (18 years of age or older) had a lower rate of ankle sprains, with an incidence of 0.72 per 1000 exposures (95% CI: 0.67, 0.77). ²

Females had an estimated incidence rate of 13.6 ankle sprains per 1000 exposures (95% CI: 13.25, 13.94), which is nearly double that of males (6.94 per 1000 exposures; 95% CI: 6.8, 7.09). ² Prevalence rates between the sexes were similar: prevalence in females was 10.99% and in males was 10.55%. ²

2. Cailbhe Doherty, Eamonn Delahunt, Brian Caulfield, Jay Hertel, John Ryan, Chris Bleakley, “The incidence and prevalence of ankle sprain injury: a systematic review and meta-analysis of prospective epidemiological studies,” Sports Medicine 44 (2014): 123-140

In the United States, ankle sprains accounted for 7.3% of all reported injuries in collegiate athletics between 2009 and 2015, occurring at a rate of 4.95 per 10,000 athlete exposures. ³ Although more than half (57.3%) of these injuries occurred during practice, there was a higher rate of ankle sprains per athletic exposure during competition. ³ The sports with the highest LLC sprain rates were men’s basketball (11.96/10,000 AEs) and women’s basketball (9.50/10,000 AEs). Most LLC sprains occurred during practices (57.3%); however, the LLC sprain rate was higher in competitions than in practices (RR, 3.29; 95% CI, 3.03-3.56). Also, 11.9% of LLC sprains were identified as recurrent injuries, with the largest proportions of recurrent LLC sprains being found within women’s basketball (21.1%), women’s outdoor track (21.1%), women’s field hockey (20.0%), and men’s basketball (19.1%). In collegiate athletes, nearly 12% of reported ankle sprains were recurrent. ³

3. Karen G. Roos, Zachary Y. Kerr, Timothy C. Mauntel, Aristarque Djoko, Thomas P. Dompier, Erik A. Wikstrom, “The epidemiology of lateral ligament complex ankle sprains in National Collegiate Athletic Association sports,” American Journal of Sports Medicine 45, no 1 (2017): 201-209

A more recent longitudinal study ⁴ found that 60% of individuals achieve resolution of activity limitations and participation restrictions by the 12-month point, with 40% progressing to develop CAI. Those with CAI are characterized by perceived instability or episodic “giving way” of the ankle that persists for more than 12 months following the initial injury and results in activity limitation and participation restriction. ⁵

4. Cailbhe Doherty, Chris Bleakley, Jay Hertel, Brian Caulfield, John Ryan, Eamonn Delahunt, “Recovery from a first-time lateral ankle sprain and the predictors of chronic ankle instability: a prospective cohort analysis,” American Journal of Sports Medicine 44, no 4 (2016): 995-1003
5. Jay Hertel, Revay O. Corbett, “An updated model of chronic ankle instability,” Journal of Athletic Training 54, no 6 (2019): 572-588

Female high school and collegiate athletes had significantly higher prevalence of CAI than their male counterparts. ⁶ A 2014 level IV study found that the prevalence of instability was significantly higher in high school athletes than in collegiate athletes. ⁶

6. Leah Tanen, Carrie L. Docherty, Barbara Van Der Pol, Janet Simon, John Schrader, “Prevalence of chronic ankle instability in high school and Division I athletes,” Foot Ankle Specialist 7, no 1 (2014): 37-44

A study of high school lacrosse players showed that females were more likely to sustain a LAS, at a rate of 2.4 per 1000 exposures versus 1.6 per 1000 exposures for males. ⁷

7. Keegan Warner, Jennifer Savage, Christopher M. Kuenze, Alexandria Erkenbeck, R. Dawn Comstock, Tracey Covassin, “A comparison of high school boys' and girls' lacrosse injuries: academic years 2008–2009 through 2015–2016,” Journal of Athletic Training 53, no 11 (2018): 1049-1055

Decreased hip extensor strength was associated with a significant (P = .028) increased risk of LAS in youth soccer players. ⁸

8. Roel De Ridder, Erik Witvrouw, Mieke Dolphens, Philip Roosen, Ans Van Ginckel, “Hip strength as an intrinsic risk factor for lateral ankle sprains in youth soccer players: a 3-season prospective study,” American Journal of Sports Medicine 45, no 2 (2017): 410-416

Decreased hip abductor strength was found to increase the risk of LAS in male soccer players, with a reported OR of 1.10 (95% CI: 1.02, 1.18). ⁹ When hip abductor strength was less than 33.8% of body weight, the probability of LAS increased from 11.9% to 26.7%. ⁹

9. Christopher M. Powers, Navid Ghoddosi, Rachel K. Straub, Khalil Khayambashi, “Hip strength as a predictor of ankle sprains in male soccer players: a prospective study,” Journal of Athletic Training 52, no 11 (2017): 1048-1055

Risk of LAS is generally increased with worse performance on unilateral standing reach tests like the Star Excursion Balance Test (SEBT) and the Y Balance Test. Better performance on the SEBT (posterolateral direction) decreased the risk of LAS (HR = 0.96; 95% CI: 0.92, 0.99). ¹⁰ When netball players reached 77.5% or less of their leg length on the posteromedial direction of the SEBT, risk of LAS was increased by more than 4 times (OR = 4.04; 95% CI: 1.00, 16.35). ¹¹ Worse performance on the anterior reach component of the Y Balance Test was associated with increased incidence of LAS in males (but not in females). ¹² In adolescent soccer players, the inability to reach at least 76% and 70% of limb length in the posteromedial and posterolateral directions, respectively, during the SEBT represented significant cutoff points indicating increased risk of LAS in the subsequent 10 months. ¹³ Asymmetrical performance (greater than 2 cm in the anterior direction, greater than 3 cm in the posteromedial and posterolateral directions, right versus left lower extremity) on the Y Balance Test was predictive of LAS in firefighters. ¹⁴

Athletes who performed the multiple hop test with more than 12 “change-in-support errors” had a 4-fold increased risk of an index LAS. ¹⁵ These “change-in-support errors” include shuffling or jumping on the support foot, removing the hands from the iliac crests, and putting the nonsupport foot down. ¹⁵

Adolescent athletes who took greater than 15.4 seconds to complete the single-leg hop test, with 10 repetitions over a 30-cm distance, were at higher risk of sustaining a LAS in the following 10 months. ¹³

In elite soccer players, poor performance (mediolateral force more than 0–0.4 seconds and/or resultant horizontal ground reaction forces more than 3–5 seconds) on a single-leg drop-jump landing was predictive of a LAS within 3 years. ¹⁶ Gait abnormalities with earlier peak pressure on the lateral forefoot, higher peak pressure under the first metatarsal, higher peak metatarsal impulse, and more medial pressure at heel-off were associated with higher risk of a LAS in military recruits. ^{17, 18}

10. M. de Noronha, L. C. França, A. Haupenthal, G. S. Nunes, “Intrinsic predictive factors for ankle sprain in active university students: A prospective study,” Scandinavian Journal of Medicine & Science in Sports 23, no 5 (2013): 541-547
11. Alison S. Attenborough, Peter J. Sinclair, Tristan Sharp, Andrew Greene, Max Stuelcken, Richard M. Smith, Claire E. Hiller, “The identification of risk factors for ankle sprains sustained during netball participation,” Physical Therapy in Sport 23 (2017): 31-36
12. Emily M. Hartley, Matthew C. Hoch, Michelle C. Boling, “Y-balance test performance and BMI are associated with ankle sprain injury in collegiate male athletes,” Journal of Science and Medicine in Sport 21, no 7 (2018): 676-680
13. Jupil Ko, Adam B. Rosen, Cathleen N. Brown, “Functional performance tests identify lateral ankle sprain risk: A prospective pilot study in adolescent soccer players,” Scandinavian Journal of Medicine & Science in Sports 28, no 12 (2018): 2611-2616
14. Jérôme Vaulerin, Frédéric Chorin, Mélanie Emile, Fabienne d’Arripe-Longueville, and Serge S. Colson, “Ankle Sprains Risk Factors in a Sample of French Firefighters: A Preliminary Prospective Study,” Journal of Sport Rehabilitation 29, no 5 (2019): 608-615
15. Christophe Eechaute, Lynn Leemans, Margo De Mesmaeker, Roel De Ridder, David Beckwée, Filip Struyf, Filip Roosen, Ronald Buyl, Koen Putman, Peter Vaes, “The predictive value of the multiple hop test for first-time noncontact lateral ankle sprains,” Journal of Sports Sciences 38, no 1 (2020): 86-93

Knee Stability

1. Ata Kiapour, “Non-Contact ACL Injuries During Landing: Risk Factors and Mechanisms,” Ph.D. thesis, The University of Toledo, Toledo, OH (2013).
2. Allison M. Ezzat, Mariana Brussoni, Louise C. Mâsse, Carolyn A. Emery, “Effect of Anterior Cruciate Ligament Rupture on Physical Activity, Sports Participation, Patient-Reported Health Outcomes, and Physical Function in Young Female Athletes,” The American Journal of Sports Medicine 49, no 6 (2021): 1460-1469.
3. Jay G. Ingram, Sarah K. Fields, Ellen E. Yard, R. Dawn Comstock, “Epidemiology of Knee Injuries Among Boys and Girls in US High School Athletics,” The American Journal of Sports Medicine 36, no 6 (2008): 1118.
4. Cindy Y. Lin, Ellen Casey, Daniel C. Herman, Nicole Katz, Adam S. Tenforde, “Sex Differences in Common Sports Injuries,” PM&R 10, no 10 (2018): 1073-1082.
5. Julie Agel, Elizabeth A. Arendt, Boris Bershadsky, “Anterior cruciate ligament injury in National Collegiate Athletic Association basketball and soccer: A 13-year review,” American Journal of Sports Medicine 33, no 4 (2005): 524-530.
6. DE Gwinn, JH Wilckens, ER McDevitt, G Ross, TC Kao, “The relative incidence of anterior cruciate ligament injury in men and women at the United States Naval Academy,” American Journal of Sports Medicine 28, no 1 (2000): 98-102.
7. Nathan A. Mall, Peter N. Chalmers, Mario Moric, Miho J Tanaka, Brian J Cole, Bernard R Bach Jr, George A Paletta Jr, “Incidence and trends of anterior cruciate ligament reconstruction in the United States,” American Journal of Sports Medicine 42, no 10 (2014): 2363-2370.
8. Elizabeth Arendt, Randall Dick, “Knee injury patterns among men and women in collegiate basketball and soccer. NCAA data and review of literature,” American Journal of Sports Medicine 23, no 6 (1995): 694-701.
9. Elizabeth A Arendt, Julie Agel, Randall Dick, “Anterior cruciate ligament injury patterns among collegiate men and women,” Journal of Athletic Training 34, no 2 (1999): 86-92.
10. Jeremy S. Frank, Peter L. Gambacorta, “Anterior Cruciate Ligament Injuries in the Skeletally Immature Athlete: Diagnosis and Management,” Journal of the American Academy of Orthopaedic Surgeons 21 (2013): 78-87.
11. Young-Mi Goo, Tae-Ho Kim, Jin-Yong Lim, “The effects of gluteus maximus and abductor hallucis strengthening exercises for four weeks on navicular drop and lower extremity muscle activity during gait with flatfoot,” Journal of Physical Therapy Science 28, no 3 (2016): 911-915.
12. Young-Mi Goo, Da-Yeon Kim, Tae-Ho Kim, “The effects of hip external rotator exercises and toe-spread exercises on lower extremity muscle activities during stair-walking in subjects with pronated foot,” Journal of Physical Therapy Science 28, no 3(2016): 816-819.
13. Yoshinori Kagaya, Yasunari Fujii, Hidetsugu Nishizono, “Association between hip abductor function, rear-foot dynamic alignment, and dynamic knee valgus during single-leg squats and drop landings,” Journal of Sport and Health Science 4, no 2 (2015): 182-187.
14. Katrina Protopapas, Stephen D Perry, “The effect of a 12-week custom foot orthotic intervention on muscle size and muscle activity of the intrinsic foot muscle of young adults during gait termination,” Clinical Biomechanics 78 (2020): 105063.
15. Karsten Hollander, Johanna Elsabe de Villiers, Susanne Sehner, Karl Wegscheider, Klaus-Michael Braumann, Ranel Venter, Astrid Zech, “Growing-up (habitually) barefoot influences the development of foot and arch morphology in children and adolescents,” Scientific Reports 7, no 8079 (2017).
16. V Sachithanandam, B Joseph, “The influence of footwear on the prevalence of flat foot. A survey of 1846 skeletally mature persons,” The Journal of Bone & Joint Surgery British Volume 77, no 2 (1995): 254-257.
17. U. B. Rao, B. Joseph, “The influence of footwear on the prevalence of flat foot. A survey of 2300 children,” The Journal of Bone & Joint Surgery British Volume 74, no 4 (1992): 525-527.
18. Nicholas B. Holowka, Ian J. Wallace & Daniel E. Lieberman, “Foot strength and stiffness are related to footwear use in a comparison of minimally- vs. conventionally-shod populations,” Scientific Reports 8, no 3679 (2018).
19. Irene S. Davis, Karsten Hollander, Daniel E. Lieberman, Sarah T. Ridge, Isabel C.N. Sacco, Scott C. Wearing, “Stepping Back to Minimal Footwear: Applications Across the Lifespan,” Exercise and Sports Science Reviews 49, no 4 (2021): 228-243.
20. Wieland Kinz, Elisabeth Groll-Knapp, Michael Kundi, “Hallux valgus in pre-school-aged children: the effects of too-short shoes on the hallux angle and the effects of going barefoot on podiatric health,” Footwear Science 13, no 1 (2021): 38-40.
21. Maisie Squibb, Kelly Sheerin, Peter Francis, “Measurement of the Developing Foot in Shod and Barefoot Paediatric Populations: A Narrative Review,” Children (Basel) 9, no 5 (2022): 750.
22. Genyu Yu, Yuzhou Fan, Yuxuan Fan, Ruining Li, Yaming Liu, Djordje Antonijevic, Petar Milovanovic, Bo Zhang, Zhiyu Li Marija Djuric and Yifang Fan, “The Role of Footwear in the Pathogenesis of Hallux Valgus: A Proof-of-Concept Finite Element Analysis in Recent Humans and Homo naledi,” Frontiers in Bioengineering and Biotechnology 8 (2020): 648.
23. Adam I. Semciw, Viji N. Visvalingam, Charlotte Ganderton, Peter Lawrenson, Paul W. Hodges, Joanne Kemp, Natalie J. Collins, “The immediate effect of foot orthoses on gluteal and lower limb muscle activity during overground walking in healthy young adults,” Gait & Posture 89 (2021): 102-108.
24. N. J. Snow, F. Basset, J. Byrne, “An Acute Bout of Barefoot Running Alters Lower-limb Muscle Activation for Minimalist Shoe Users,” International Journal of Sports Medicine 37, no 5 (2016): 382-387.
25. Tom Linner, Casey Murphy, Jeremy O'Keefe, "Barefoot Training: Effects on EMG Activity of Gluteus Medius and Tensor Fascia Latae in Habitually Shod Runners" Physical Therapy Scholarly Projects (2019): 684.
26. Naruto Yoshida, Shun Kunugi, Takehiro Konno, Akihiko Masunari, Satoru Nishida, Takashi Koumura, Naoyuki Kobayashi, and Shumpei Miyakawa, “Differences in Muscle Activities and Kinematics between Forefoot Strike and Rearfoot Strike in the Lower Limb during 180° Turns,” International Journal of Sports Physical Therapy 16, no 3 (2021): 715-723.
27. Timothy E. Hewett, Kevin R. Ford, Gregory D. Myer, “Anterior Cruciate Ligament Injuries in Female Athletes Part 1, Mechanisms and Risk Factors,” The American Journal of Sports Medicine 34, no 2 (2006): 299-311.
28. Kao-Shang Shih, Hui-Lien Chien, Tung-Wu Lu, Chu-Fen Chang, Chien-Chung Kuo, “Gait changes in individuals with bilateral hallux valgus reduce first metatarsophalangeal loading but increase knee abductor moments,” Gait and Posture 40, no 1 (2014): 38-42.
29. Sarah T. Ridge, Mark T. Olsen, Dustin A. Bruening, Kevin Jurgensmeier, David Griffin, Irene S. Davis, A. Wayne Johnson, “Walking in Minimalist Shoes Is Effective for Strengthening Foot Muscles,” Medicine & Science in Sports & Exercise 51, no 1 (2019): 104-113.
30. Tony Lin-Wei Chen, Louis K Y Sze, Irene S Davis, Roy T H Cheung, “Effects of training in minimalist shoes on the intrinsic and extrinsic foot muscle volume,” Clinical Biomechanics 36 (2016): 8-13.
31. Elizabeth E. Miller, Katherine K. Whitcome, Daniel E. Lieberman, Heather L. Norton, Rachael E. Dyer, “The effect of minimal shoes on arch structure and intrinsic foot muscle strength,” Journal of Sport Health and Science 3, no 2 (2014): 74-85.
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35. Shayan Quinlan, Alycia Fong Yan, Peter Sinclair, Adrienne Hunt, “The evidence for improving balance by strengthening the toe flexor muscles: A systematic review,” Gait & Posture 81 (2020): 56-66.
36. Karsten Hollander, Astrid Zech, Ranel Venter, Johanna E. de Villiers, Susanne Sehner, Karl Wegscheider, “Motor Skills of Children and Adolescents Are Influenced by Growing up Barefoot or Shod,” Frontiers in Pediatrics 6 (2018): 115-120.
37. Jun Mizushima, Justin W.L. Keogh, Kei Maeda, Atsushi Shibata, Jun Kaneko, Keigo Ohyama-Byun, Mitsugi Ogata, “Long-term effects of school barefoot running program on sprinting biomechanics in children: A case-control study,” Gait & Posture 83 (2021): 9-14.
38. Shayan Quinlan, Peter Sinclair, Adrienne Hunt, Alycia Fong Yan, “The long-term effects of wearing moderate minimalist shoes on a child’s foot strength, muscle structure and balance: A randomised controlled trial,” Gait & Posture 92 (2022): 371-377.
39. Priyanka Amit Kumar, Subhra Basu, Manjunatha H, “Effect of Gluteus Maximus and Abductor Hallucis Muscle Strengthening on Balance in Pediatric Over Pronated Foot,” International Journal of Health Sciences and Research 12, no 10 (2022): 154-159.
40. N. J. Snow, F. Basset, J. Byrne, “An Acute Bout of Barefoot Running Alters Lower-limb Muscle Activation for Minimalist Shoe Users,” International Journal of Sports Medicine 37, no 5 (2016): 382-387.
41. Tom Linner, Casey Murphy, Jeremy O'Keefe, "Barefoot Training: Effects on EMG Activity of Gluteus Medius and Tensor Fascia Latae in Habitually Shod Runners" Physical Therapy Scholarly Projects (2019): 684.
42. Gregory D. Myer, Dai Sugimoto, Staci Thomas, Timothy E. Hewett, “The Influence of Age on the Effectiveness of Neuromuscular Training to Reduce Anterior Cruciate Ligament Injury in Female Athletes: A Meta-Analysis,” The American Journal of Sports Medicine 41, no 1 (2013): 203-215.
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45. Naruto Yoshida, Shun Kunugi, Sonoko Mashimo, Yoshihiro Okuma, Akihiko Masunari, Shogo Miyazaki, Tatsuya Hisajima, Shumpei Miyakawa, “Effect of Forefoot Strike on Lower Extremity Muscle Activity and Knee Joint Angle During Cutting in Female Team Handball Players,” Sports Medicine – Open 2, no 32 (2016).
46. Joe P. Warne and Allison H. Gruber, “Transitioning to Minimal Footwear: a Systematic Review of Methods and Future Clinical Recommendations,” Sports Medicine – Open 3(1), no. 33 (2017): 12.
47. Erin E. Futrell, K. Douglas Gross, Darcy Reisman, David R. Mullineaux, Irene S. Davis, “Transition to forefoot strike reduces load rates more effectively than altered cadence,” Journal of Sport and Health Science 9, no. 3 (2020): 255-256.
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