Association between running biomechanics and lower limb musculotendinous changes over an adolescent marathon training program

Prospective musculotendinous changes have been observed among adolescents completing marathon training programs. However, examinations of potential factors influencing musculotendinous characteristics do not currently exist. Evaluations of biomechanical parameters and the influence on musculotendinous features and changes over time are warranted. What are the relationships between adolescent running biomechanics and 1) lower extremity musculotendinous characteristics cross-sectionally, and 2) changes in musculotendinous properties over 6-months? Thirty-three adolescent runners participated in this study (19 F, 14 M; 15.8 ± 1.6 years). Ultrasound images of lower extremity musculotendinous structures were obtained to determine thickness and echogenicity. Following ultrasound measures, outdoor running biomechanics were assessed using wearable sensors to collect spatiotemporal, kinetic, and kinematic measures. A subset of participants had repeat ultrasound evaluations following a 6-month running program (n = 11; 6 F, 5 M). Hierarchical linear models were used to assess the relationships between biomechanics and ultrasound measures. Pearson’s correlations were used to assess the relationship between biomechanics the change in musculotendinous characteristics (baseline to 6-months). The strongest relationships between measures were for the Achilles tendon (R2=0.39, F=0.85, p = 0.10), and flexor digitorum brevis (R2=0.38, F=2.38, p = 0.06). The interaction between pronation excursion and velocity was a significant predictor for Achilles tendon thickness (p = 0.03), and medial gastrocnemius thickness (p = 0.05). Contact time was a significant predictor for intrinsic foot muscle thickness (p = 0.01). There were moderate correlations across biomechanical measures and changes in musculotendinous thickness and echogenicity. Biomechanical characteristics often noted with running-related injuries were moderately related to tissue-level characteristics, and changes during running training. •Biomechanical sensors and ultrasound units were used to assess adolescent runners.•Pronation during running was related to Achilles tendon thickness and echogenicity.•Lower contact time during running was linked with larger intrinsic foot muscles.•Biomechanics related to musculotendinous health may guide clinical intervention.