Effects of 8-weeks selective training on the peroneus longus and peroneus brevis morphologies

Resistance training for the peroneus muscles is important because this muscles undergo morphological changes and functional decline after a lateral ankle sprain. We reported at last year's ESMAC 2022 the possibility of selectively training each muscle by implementing immediate selective interventions for the peloneus long (PL) and peroneus brevis (PB) (Arima et al., 2022). However, it has not been examined whether long-term interventions can selectively train the PL and PB. Does an 8-weeks intervention allow selective training of the PL and PB? Eighteen healthy participants were divided into two task groups that performed two different 3 times a week for 8-weeks tasks: the PL task in which a Thera-Band was placed on the ball of the foot and pushed out from the contact point (n=9), and the PB task in which the Thera-Band was pulled out from the base of the fifth metatarsal (n=9). Muscle cross-sectional area (CSA) at 25% (showing PL) and 75% (showing PB) proximal to the line connecting the fibular head and lateral malleolus measured by an ultrasound system, and PL and PB strength measured using a handheld dynamometer were determined at the beginning of week 1 (baseline) and on the first day of the week following each weekly task. PL and PB strength measured muscle strength during exercise of the same as PL and PB tasks. Two-way ANOVA was used to check for differences in changes in values by the 8-weeks PL and PB tasks. There was significant interaction between groups and measurement weeks for the 25% and 75% CSA, PL and PB strength (p<0.05). Post hoc test showed that the 25% CSA was significantly higher in the PL task between weeks 3 and 8 compared to baseline (p<0.05). The 75% CSA was significantly higher in the PB task compared to baseline for all weeks between weeks 4 and 8 (p<0.05). PL strength was significantly higher in the PL task between weeks 2 and 8 compared to baseline (p<0.05). PB strength was significantly higher in the PB task compared to baseline for all weeks between weeks 3 and 8 (p<0.05). PL muscle activity is increased by the ball of the foot loading, and the PB contributes to ankle eversion compared to the PL. In this study, the 8-week intervention also increased 25% CSA and PL muscle strength in the PL task over time with each passing week, and 75% CSA and PB muscle strength in the PB task. This suggests that an 8-weeks PL and PB tasks probably be useful for long-term selective training of peroneus muscles.