Relationships of Ultrasound Measures of Intrinsic Foot Muscle Cross-sectional Area and Muscle Volume with Maximum Toe Flexor Muscle Strength and Physical Performance in Young Adults

[Purpose] To investigate the relationships between toe flexor muscle strength with (TFS-5-toes) and without (TFS-4-toes) the contribution of the great toe, anatomical and physiological muscle cross-sectional areas (CSA) of intrinsic toe flexor muscle and physical performance were measured. [Subjects] Seventeen men (82% sports-active) and 17 women (47% sports-active), aged 20 to 35 years, volunteered. [Methods] Anatomical CSA was measured in two intrinsic toe flexor muscles (flexor digitorum brevis [FDB] and abductor hallucis) by ultrasound. Muscle volume and muscle length of the FDB were also estimated, and physiological CSA was calculated. [Results] Both TFS-5-toes and TFS-4-toes correlated positively with walking speed in men (r=0.584 and r=0.553, respectively) and women (r=0.748 and r=0.533, respectively). Physiological CSA of the FDB was significantly correlated with TFS-5-toes (r=0.748) and TFS-4-toes (r=0.573) in women. In men, physiological CSA of the FDB correlated positively with TFS-4-toes (r=0.536), but not with TFS-5-toes (r=0.333). [Conclusion] Our results indicate that physiological CSA of the FDB is moderately associated with TFS-4-toes while toe flexor strength correlates with walking performance.