Background: Toe flexor muscle strength determines the anterior limit of the functional base of support, thereby affecting a standing individual's maximum forward reach or lean capacity. We developed a method for measuring toe flexor muscle strength in order to test the null hypotheses that it is neither affected by age nor gender.
Methods: Gender-balanced groups of 20 healthy young adults (YA) (average age 22.8 years) and 20 healthy older adults (OA) (average age 73.2 years) participated in the study. Toe flexor isometric muscle strength, calculated as the maximum volitional moment developed simultaneously in the sagittal plane by the toe flexor muscles about a reference axis through the first metatarsophalangeal joint, was measured in three trials while subjects reached forward as far as possible while standing on a force plate.
Results: Significant age (p <.005) and gender (p <.0005) differences were found in maximum toe flexor muscle strength. OA were 28.9% less strong than the YA [mean (SD) 13.5 (5.7) Nm and 19.0 (6.8) Nm, respectively]. The men developed 39.1% greater strength than the women [20.2 (7.1) Nm and 12.3 (3.7) Nm, respectively]. However, when normalized by body size (body weight x height), the gender difference in strength no longer reached statistical significance. Across all subjects, the anterior limit of the functional base of support was significantly correlated with toe flexor strength (coefficient of determination: 0.84).
Conclusions: Toe flexor muscle strength decreased significantly with age. This decrement underlies the known age-related reduction in the functional base of support.