Unfavorable Achilles Tendon Morphological Quality And Mechanics In Collegiate Army ROTC Cadets

College Army Reserve Officer Training Corps (ROTC) cadets enter military service as officers, who demonstrate elevated Achilles tendon injury rates and risk compared to athletes and other service members. However, musculotendinous mechanical and quality characteristics are unknown within this at-risk cohort prior to service. PURPOSE: Evaluation of site-specific musculotendinous morphology and mechanics using ultrasonography and dynamometry in ROTC cadets during a pivotal pre-service period. METHODS: ROTC cadets (n = 32; male = 26, female = 6) were compared with physically active (≥3 d/wk) sex, age (±1 year), and body mass (±1 kg) matched controls. Voluntary informed consent, exercise and sleep logs, and anthropometrics, were collected prior to B-Mode ultrasound scans of the gastrocnemii and Achilles tendon, assessing musculotendinous length, cross-sectional area (CSA) and echogenicity (EI). This coincided with isometric dorsi/plantarflexion dynamometry to determine Achilles tendon elastic modulus (EM). Independent t-tests compared group differences, Pearson’s bivariate correlations determined ROTC tendon associations, Cohen’s d effect sizes were calculated, and α = 0.050. RESULTS: Groups were similar for anthropometrics and muscle EI (all p ≥ 0.124; d ≤ 0.28), however, controls had larger muscle CSA (both p ≤ 0.002; d ≥ 0.82). Cadets demonstrated greater dorsiflexion-to-plantarflexion force ratio and Achilles EM (all p < 0.001; d ≥ 0.76, Fig. 1 top), however, Achilles EI was reduced (p < 0.001; d = 1.97, Fig. 1 middle), indicating fibrous disorientation, compared to controls. Additionally, associations were found between Achilles EM and EI (r = -4.06; p = 0.030), and EM and sleep quality (r = 0.450; p = 0.016, Fig. 1 bottom). CONCLUSIONS: These findings denote ROTC tendon rigidity was influenced by structural disorientation and poor sleep quality; indicating unfavorable pre-service tendon and general health traits within this at-risk military cohort.