## Discussion
Differences between the previous research and this study which may provide some rationale for the differences in findings include the tendon being examined (patella vs AT), the method of obtaining stiffness measures (ultrasonography and isokinetic dynamometer vs SWE) and differences in populations studies (purely male cohort vs mixed sex cohort). SWE as a methodology has been validated against traditional tensile testing [36] and the results of this study showed no significant differences between the SWV of males and females, so the use of a differing cohort should not impact the results. To assess the effect of leg dominance on SWE measures of the AT, the dominant and non-dominant ATs of each participant were identified [38], with the majority of people identifying their right foot as being dominant [39]. As an association between full rupture in the AT and micro-tear formation has been previously shown, it would indicate that the ATs of the dominant side will be more at risk of both micro-tear and full rupture [48]. This increase in micro-tears is hypothesised to result in tendon hypertrophy as the tendon constantly repairs and remodels itself [48], which would explain a higher cross-sectional area of tendon noted in athletes compared to the general population [26]. An increased thickness can also be a result of short-term injury which can result in tendon thickening in an attempt to reduce stress [28]. Some research has shown no significant variation in the length of the AT between dominant and non-dominant ankles [38], however in contrast, other authors have found the length of the free AT of the dominant leg to be significantly greater than the non-dominant leg [39]. These two studies also differ in their findings in relation to the cross-sectional area of the AT. One study found no significant difference in the average cross-sectional area of the free AT between legs [39] whereas others demonstrate cross-sectional area to be significantly larger in dominant ankles [38], which can impact stiffness. The [PERSON] et al. (2015) reported no significant differences between the sides in tendon stiffness (N/mm) [39] as found in this current study. In the present study, no noted significant differences (\(p\) > 0.05) in stiffness measures were obtained with SWE were found in healthy, asymptomatic subjects with no history of symptomatic Achilles tendinopathy, between dominant and non-dominant tendons. The mean increase in SWV following the exercise bout was 0.27 m/s with the range of increase for all participants being between 0.05-0.81 m/s. This was followed by a decrease between the post measure and 6 h measure of \(-\)0.43 m/s. These alterations were shown to be statistically significant, therefore just 30 min of running was shown to significantly increase SWV by 0.27 m/s, and therefore increase AT stiffness. Studies using UTC have shown that exercise leads to a change in tendon structure in both race horses and humans [25; 49] when tendons were measured prior to the bout of exercise, then again one, two and four days after the exercise bout. Changes in the structure of the tendon may be expected to affect its mechanical properties, e.g., tendon stiffness and this study adds some support to that notion as exercise resulted in a significantly increased measure of SWV, even after an acute bout of exercise lasting 30 min. In the UTC study involving human participants, the authors concluded that exercise resulted in a short-duration (72 h period) and fully reversible response of the tendon which occurred with no loss of integrity of the collagen matrix [25]. Alterations in the extra-cellular matrix of the tendon including an increase in cytoplasmic organelles for increased protein production, in particular proteoglycans, which are associated with an increase in bound water can result in an increase in cross-sectional area after exercise [28].