Muscle strength as an indicator of the habitual level of physical activity.

This study focused on age and physical activity as determinants of muscle strength. The study involved 620 women 25-73 yr of age. The five muscle groups assessed were: grip, plantarflexors, hip abductors, trunk flexors, and trunk extensors. Pearson correlations yielded significant negative correlations of muscle strength with age and positive correlations with height as well as physical activity. The greatest decremental differences in muscle strength were registered in the perimenopausal years between the age decades of 45-54 yr and 55-64 yr. In stepwise regression analyses age was the strongest predictor of the strength of all muscle groups, with smaller contributions to the variance by physical activity and anthropometric variables. When the sample population, divided by decades of age, was further subdivided by tertiles of physical activity, the results of factorial analysis indicated that the main effects due to age and physical activity were significant. It was concluded that 1) moderate levels of physical activity tend to improve muscle strength even in older women, and 2) normative values of muscle strength could serve as an indicator of the adequacy of the habitual levels of physical activity.