Comparison of Change in Achilles Tendon Size Between Male Long-Distance Runners and Water Polo Players

Achilles tendon (AT) tendinopathy is a common condition in athletes, particularly in runners (R). While research exists on tendon adaptations in R (decrease in cross-sectional-area (CSA) in male R), less is known about adaptations in the tendons of aquatic athletes. We hypothesized the change in CSA in R before and after training to be larger compared to the aquatic athletes because of the greater loading forces acting on the AT. Purpose: To compare changes in AT CSA in male athletes, water polo players (WP) and long-distance R, before and after a single bout of sport-specific exercise. Methods: 40 WP (age= 16 ± 1.5 yrs; wt= 77.4 ± 12.9 kg; ht= 183.4 ± 7.7 cm) and 31 R (age= 22.7 ± 2.7 yrs; wt= 71.1 ± 7.8 kg; ht= 178.7 ± 7.1 cm) were imaged using ultrasound (GE Logiq e with an L8-18i transducer) before and immediately after typical sport-specific exercise. CSA images from each imaging session were measured twice by the same person and averaged. Results: WP had larger tendon CSA at the pre-measurement (WP 0.548 ± 0.079 cm2; R 0.515 ± 0.068 cm2) and experienced a greater decrease in CSA compared to R when accounting for height (R: pre: 178.7 ± 7.1 cm, WP 183.4 ± 7.7 cm) (p= 0.037). Two WP demonstrated a large decrease in CSA that influenced the difference in overall CSA change between WP and R. When these two players were removed, the difference between WP and R was no longer present (p=0.12). It is important to note that R ran for approximately 45 minutes while WP were in the water for 90-120 minutes. Conclusion: Our hypothesis was rejected; the aquatic athletes demonstrated a greater change in CSA after their workout. Two conclusions are possible: 1. loading forces experienced by WP were sufficient to elicit change in AT CSA, or 2, the amount of time in the water had a significant effect on tendon CSA change. Other factors that may have influenced the results are the difference in exercise duration and the age difference between the groups.