Electromyographic investigation of exercises that strengthen the foot's arch

The abductor hallucis (ABDH) and tibialis posterior (TP) support the medial longitudinal arch and are frequently targeted in foot strengthening programs, but exercise selection lacks evidence-based criteria. This study examined which commonly prescribed foot exercises preferentially recruit TP and ABDH relative to secondary synergists. Ten healthy adults (5 self-reported female, 5 self-reported male) with no lower-limb pathology performed 14 ft and ankle exercises, including short-foot variations, heel raises, toe spreading, toe dissociation, towel-based tasks, and walking. Fine-wire and surface electromyography recorded activity of TP, ABDH, tibialis anterior, flexor hallucis longus, and flexor digitorum longus. Signals were normalized to peak dynamic activity and used to compute an activation ratio (AR) comparing combined ABDH and TP activation with secondary synergists. Three-dimensional kinematic data characterized ankle and rearfoot positions at peak TP and ABDH activation. Ten exercises produced an AR > 1.0, indicating greater combined activation of ABDH and TP than secondary synergists. Toe spreading and flexed toe dissociation yielded the highest ARs, whereas normalized ABDH amplitude was greatest during unilateral heel raise and hopping short-foot exercises. For TP, walking and a resisted plantarflexion-inversion towel slide (PFIN) showed the highest ARs, while PFIN and unilateral heel raise produced the greatest normalized TP amplitudes. These findings characterize the neuromuscular demands of common foot exercises in healthy adults and may inform the design of future intervention studies.