Achilles Tendon Cross Sectional Area Changes Over a Division I NCAA Cross Country Season.

Tracking Achilles tendon cross sectional area (CSA) changes may help clinicians understand exercise adaptations and Achilles tendon injury mechanisms. To track adaptations in the Achilles tendon in response to a cross country season.

Design: Longitudinal study. Musculoskeletal (MSK) ultrasound images were obtained in a research laboratory. Cross country athletes ran with no restrictions outdoors and indoors. Participants were Division I NCAA cross country athletes (N = 24, age = 19.9 ± 2.1 years, mass = 61.32 ± 20.16 kg, height = 168.92 ± 17.16 cm, sex = 8 males and 16 females). Achilles tendon CSA was obtained through MSK ultrasound imaging at a pre-season baseline measurement, every 3 weeks throughout the season, and at post-season for a total of 4 measurements. Participants followed their normal running regimen outlined by their cross country coach. The dependent variable was Achilles tendon CSA measured by ultrasound imaging. We used a repeated measures ANCOVA to determine differences in CSA over the cross country season. CSA increased from baseline (0.439 ± .081 cm), to 0.466 ± 0.096 cm at 3-weeks, to 0.471 ± 0.092 cm 6-weeks, and decreased to 0.451 ± 0.104 cm at the post-season measurement. The 3-week and 6-week measures significantly increased from baseline (F3,72 = 8.575, p < .001). Achilles tendon CSA increased during the cross country season, but returned to baseline values at the end of a cross country season. Clinicians should be aware of the changing nature of the Achilles tendon CSA when treating cross country runners.