Electromyographic activation of extrinsic and intrinsic foot muscles during nine different foot exercises in women with hallux valgus: a cross-sectional comparative study

Hallux valgus (HV) is associated with altered activation of intrinsic and extrinsic foot muscles, which may be relevant to rehabilitation planning. Understanding task-specific muscle activation during commonly prescribed exercises may help inform exercise selection. This study aimed to compare the electromyographic activity of the abductor hallucis (ABH), peroneus longus (PL), flexor hallucis longus (FHL), and extensor hallucis longus (EHL) muscles during nine foot exercises in women with HV. Seventeen women with moderate-to-severe hallux valgus (22.2 ± 3.1 years) performed nine exercises: sitting short-foot, standing short-foot, single-leg short-foot, towel curl, toe-spread-out, three-dimensional foot–ankle extension in diagonals 1 and 2 (3DFA-D1E and 3DFA-D2E) patterns, calf raise, and stand swing. Surface electromyography signals were recorded from the ABH, PL, FHL, and EHL muscles. The signals were processed using a 150-ms moving root mean square (RMS) window. The mean RMS amplitude calculated from the middle three seconds of the 5-s sustained contraction phase was used for analysis. Significant differences in EMG amplitude were observed across exercises for all evaluated muscles (p < 0.001). ABH showed relatively lower activation during towel curl (p < 0.05), and higher activation during single-leg short-foot, toe-spread-out, and stand swing (p < 0.05). PL activation was highest during calf raise and 3DFA-D1E. FHL activation was highest during towel curl, 3DFA-D1E and 3DFA-D2E (p < 0.01), and calf raise, whereas sitting short-foot and toe-spread-out elicited relatively low FHL activation (p < 0.01). EHL showed highest activation during single-leg short-foot and toe-spread-out than during several other exercises (p < 0.05). These findings provide preliminary information on task-specific muscle activation patterns during commonly prescribed foot exercises in women with HV. Exercises such as single-leg short-foot, toe-spread-out, calf raise, stand swing, and 3DFA extension may help inform muscle-targeted exercise selection in HV rehabilitation; however, the long-term clinical effects of these exercises require confirmation in longitudinal and interventional studies.