Sex Differences in Muscle Hypertrophy Response to Training of the Peroneus Longus and Peroneus Brevis Muscles

Abstract

Category: Ankle; Trauma Introduction/Purpose: It has been reported that there are no significant sex differences in muscle hypertrophy response after strength training for the quadriceps muscles (Roth et al., 2002). After an ankle sprain, the peroneus longus (PL) and peroneus brevis (PB) muscles develop morphological changes and dysfunction, which requires training for the PL and PB (Arima et al., 2022). However, to our knowledge, sex differences in muscle hypertrophic response to the PL and PB training have not been studied. This study aimed to compare the changes in muscle cross-sectional area (CSA) after the PL and PB training between men and women, and to examine the possible influence of sex on the muscle hypertrophy response to training for the PL and PB. Methods: Eighteen healthy adults (9 men and 9 women) were participated. All participants performed two types of ankle eversion training on the right leg with Thera-Band on separate days. PL training in which the Thera-Band was placed on the ball of foot and pushed out from the contact point, and PB training in which the Thera-Band was pushed out from the base of the fifth metatarsal. An ultrasound imaging device was used to measure the CSA of the peroneal muscles at the proximal 25% and distal 75% of the line connecting the fibular head and the lateral malleolus. The measurements were taken before (pre), immediately after (post), 10, 20, and 30 minutes after each training, and the amount of change over time relative to pre was calculated. Unpaired t-tests were used to compare the change in CSA between men and women at each time. Statistical significance was set at 5%. Results: After the PL training, the amount of change in CSA of the PL was significantly greater by 29.7 mm² in women than in men only at post (p < 0.05), but there were no significant differences at other times (10 minutes: p = 0.06, 20 minutes: p = 0.19, 30 minutes: p = 0.11). After the PB training, the amount of change in CSA of the PB was significantly greater by 16.0 mm² at post (p < 0.05) and 3.1 mm² at 30 minutes (p < 0.01) in women than in men. However, there were no significant differences at 10 and 20 minutes (10 minutes: p = 0.27, 20 minutes: p = 0.55). Conclusion: The results indicate that sex differences may influence the immediate muscle hypertrophic response to training for the PL and PB. The immediate muscle hypertrophy response after training is due to edema resulting from muscle damage, reflecting an immediate effect of training (Damas et al., 2016), which suggests that women are more likely to achieve effects of the PL and PB training than men in similar loads. Furthermore, the results also show that the effect of the PB training may be maintained longer in women, thus it is necessary to investigate the long-term effects of the training in the future.