Acute Effects in Selective Training of the Peroneus Longus and Peroneus Brevis
Authors: Arima Satoshi , Maeda Noriaki , Oda Sakura , Tamura Yuki , Komiya Makoto , Urabe Yukio 
Published: December 2023

Category: Other Introduction/Purpose: The peroneal muscles undergo morphological changes and functional decline after a lateral ankle sprain, contributing to recurrence. We reported that different morphological changes occur in the peroneus longus (PL) and peroneus brevis (PB) after the lateral ankle sprain (Arima et al., 2022), and we believe that separate strength training for the PL and PB is necessary. However, the effect of selective training has not been studied. This study examined the acute effects of two different strength training interventions on PL and PB muscle morphology, one emphasizing loading on the ball of foot in PL training and the other emphasizing ankle eversion in PB training. The aim was then to determine the validity of selective strength training interventions for the peroneal muscles. Methods: Twenty healthy adults participated. Two training interventions were performed using a Thera-Band (strength: level +3 (black), Sakai Medical) in the right leg on separate days: the PL intervention in which the Thera-Band was placed on the ball of foot and pushed out from the contact point, and the PB intervention in which the Thera-Band was pushed out from the base of the fifth metatarsal. Muscle cross-sectional area (CSA) and thickness of the peroneus muscles at the proximal 25% (showing PL) and 75% (showing PB) from the line connecting the fibular head and lateral malleolus were measured with an ultrasound device. Measurements were taken before (Pre), immediately after (Post), and 10, 20, and 30 minutes after the intervention (time effect). A repeated measures two-way ANOVA was conducted to identify differences in the training effects of PL and PB interventions on PL and PB CSA, thickness. The significance level was 5%. Results: Significant main effects of time and intervention and a significant interaction between time and intervention were found in the proximal 25% and distal 75% CSA and thickness (p < 0.05). For the proximal 25% CSA, only PL intervention significantly increased the CSA compared to Pre at Post, 10 and 20 minutes (p < 0.05). With regard to the proximal 75% CSA, only PB intervention significantly increased the CSA compared to Pre at Post, 10 and 20 minutes (p < 0.05). For the proximal 25% thickness, only PL intervention showed a significant increase in Post compared to Pre (p < 0.05). Regarding proximal 75% thickness, only PB intervention significantly increased the thickness compared to Pre at Post, 10, and 20 minutes (p < 0.05). Conclusion: Previous studies have reported that PL muscle activity is increased by the ball of foot loading (Ishida et al., 2011), and the PB contributes to ankle eversion compared to the PL (Otis et al., 2007). Transient muscle hypertrophy immediately after training is due to edema caused by muscle damage, indicating an acute effect of training (Damas et al., 2016). The CSA and thickness of the proximal 25% showing PL in the PL intervention and the distal 75% showing PB in the PB intervention increased immediately after those interventions in this study, suggesting the possibility of selectively training PL and PB.