Adolescent exercise-related lower leg pain musculotendinous characteristics.

ABSTRACT

BACKGROUND: Exercise-related lower leg pain (ERLLP) is one of the most common injuries among adolescent runners; however, there is limited information available on lower extremity musculotendinous characteristics in relationship to injury. Ultrasound imaging has previously been used to evaluate musculotendinous structures among adults with chronic lower limb injuries. Similar measurement approaches may be adopted to assess young runners with ERLLP. OBJECTIVE: To compare ultrasound-derived lower extremity musculotendinous thickness, echogenicity, and muscle fiber pennation angles between adolescent runners with and without ERLLP. DESIGN: Cross-sectional design. SETTING: Hospital-affiliated sports injury prevention center. PARTICIPANTS: Twenty-eight adolescent runners with (N = 14) and without ERLLP (N = 14). INTERVENTIONS: Runners' patellar and Achilles tendons, and tibialis anterior, medial gastrocnemius, abductor hallicus, and flexor digitorum brevis muscles were assessed with ultrasound imaging using standardized procedures. MAIN OUTCOME MEASURES: Separate repeated measures multivariate analyses of covariance (covariate gender) were used to compare groups and limbs for mass-normalized musculotendinous thickness, musculotendinous echogenicity, and extrinsic ankle muscle fiber pennation angles. RESULTS: The adolescent ERLLP group had reduced average muscle size for all structures except the tibialis anterior compared to the uninjured group (mean difference [MD] range -0.12-0.49 mm/kg; p range .002-.05), and reduced average medial gastrocnemius pennation angles on their case limb compared to their contralateral limb and the uninjured group (MD range -3.7-6.4°; p < .001). The ERLLP group additionally had reduced average patellar and Achilles tendon size (MD range -0.14--0.15 mm/kg; p range .02-.03), and lower Achilles tendon echogenicity compared to uninjured counterparts (MD -18; p = .02). CONCLUSIONS: Adolescent runners with ERLLP exhibited morphological musculotendinous changes that may occur either as a result of or as a contributing factor to pain and persistent dysfunction. The findings highlight key targets for rehabilitation for young, injured runners, particularly intrinsic foot muscle strengthening.