Seasonal Achilles Tendon Injury Risk And Musculoskeletal Adaptations In Division I Cross-country And Track Athletes

Cross-Country and Track (XCT) athletes’ training volume is often dictated by season, eliciting lower body musculoskeletal adaptations; but how these alterations impact seasonal injury risk is unknown. PURPOSE: To evaluate site-specific musculotendinous characteristics using diagnostic ultrasonography and musculoskeletal indices using Dual-energy X-ray Absorptiometry (DXA) in NCAA Division I XCT athletes across competitive seasons. METHODS: XCT athletes (n = 23) were assessed pre/post cross-country and post outdoor (n = 14) seasons. Voluntary informed consent, injury, training, and NSAID use logs were collected prior to a total body DXA scan with shank region of interest (ROI; tibial plateau to distal foot), for bone and body composition measures. Real-time brightness mode ultrasonography assessed cross-sectional area (CSA), thickness (TH), pennation angle (PA), and subcutaneous fat-corrected echo intensity (EI) for the bilateral gastrocnemii and tibialis anterior coinciding with multi-site TH, CSA, and EI of the Achilles tendon. Repeated Measures ANOVA compared seasonal differences. Cohen’s d effect sizes were calculated and α = 0.050. RESULTS: Bilateral musculature CSA, PA, and EI increased pre/post XC (all p ≤ 0.001; d:0.48-0.87), coinciding with increased Achilles tendon CSA and TH (all p < 0.001; d:0.23-0.88) and reduced EI (all p < 0.001; d:0.65-0.87) across all sites. However, all measures returned to near pre-XC levels post-outdoor (all p ≤ 0.048; d: 0.24-1.07; Figure 1). Bone indices and body composition remained unchanged all year (all p ≥ 0.097; d: 0.01-0.14). CONCLUSION: These data indicate an elevated seasonal Achilles tendon injury risk from increased intramuscular adiposity corresponding with a thicker, less fibrous tendon. Detrimental adaptations coincided with sustained high mileage and NSAID use but subsided concurrently with reduced mileage and drug use; warranting across-season evaluation for precise injury risk assessment.