Introduction The Achilles tendon is an elastic storage tendon that converts kinetic energy into mechanical energy and reduces the metabolic cost of high-speed locomotion. Numerous studies have shown that the tendon is responsive to mechanical stimuli with changes in CSA and collagen synthesis both in the short- and long-term.1 ,2 This mechano-responsiveness of the tendon has been implicated in the development of tendinopathy and detecting early and/or short-term changes may have a role in managing tendinopathy. Ultrasound tissue characterisation (UTC) uses contiguous ultrasound images to render a 3-dimensional image that allows semi-quantitative analysis of tendon structure. This novel ultrasound technique has been used to show short-term changes in tendon structure in response to maximal exercise in thoroughbred horses.3 This study aims to investigate short-term changes in the Achilles tendon in Australian football players in response to loading during competitive games.

Methods 22 elite male Australian football players, some with history of tendinopathy (six and three players with a history of patellar and Achilles tendinopathy, respectively) were recruited. Players were scanned prior to the game and days 1, 2 and 4 post-game using UTC. A 1cm region at the midsubstance of the tendon was selected and the ultra-structure quantified into four echo-types based on the stability of the echopattern. Changes in the echopattern were compared over the 4 days using a related samples Friedmans two-way analysis of variance. If a significant difference in the median was observed, post-hoc (Wilcoxon signed rank test) analysis was performed to identify the differences between days 1, 2 and 4 and day 0.

Results Preliminary data analysis showed differences in baseline tendon structure in players with and without a history of lower limb tendinopathy. Further analysis will examine differences between groups in change over the 4 days, and examine intrinsic (age, mass) and extrinsic factors (game load, GPS data) that are associated with change in UTC parameters.

Conclusions This study demonstrated the changes seen in the Achilles tendons of athletes after intense loading. The factors that affect the magnitude of the response were elucidated.