Strength and size relationships of toe flexor muscles with special reference to the toes intended for force production

Toe flexor strength (TFS) has been shown to be associated with the size of toe flexor muscles. However, it is unclear how the relationship between muscle size and TFS varies depending on the toe(s) intended for force production. We hypothesized that the TFS produced by all toes (TFS-All), the great toe (TFS-Great), and lesser toes (TFS-Lesser) would be specifically associated with the size of the muscles specialized in each toe flexion. The maximal anatomical cross-sectional area (ACSA max ) of each toe flexor muscle was measured by magnetic resonance imaging in fifteen healthy young men. The three TFS were measured using a custom-made toe push dynamometer. TFS-All was significantly associated with ACSA max of the flexor hallucis brevis (r = 0.570, P = 0.026). However, the TFS-Great and TFS-Lesser showed no significant correlation with the ACSA max of any muscles. The current results indicate that the magnitude of TFS, depending on the toes intended for force production, is not associated with the size of the muscles specialized in each toe flexion. This may be attributed to the difficulties separately producing TFS with the great toe and lesser toes, potentially due to decreased voluntary activation and/or mechanically connected tendons in the toe flexor muscles.