Purpose: The purpose of the study was to examine the relation between serum 25-hydroxy vitamin D (25(OH)D) levels and muscle strength in 419 healthy men and women over a broad age range (20–76 yr).
Methods: Isometric and isokinetic strength of the arms and legs was measured using computerized dynamometry, and its relation to vitamin D was tested in multivariate models controlling for age, gender, resting HR, systolic blood pressure, diastolic blood pressure, body mass index, maximal oxygen uptake (V˙O2max,), physical activity counts, and season of vitamin D measurement.
Results: Vitamin D was significantly associated with arm and leg muscle strength when controlling for age and gender. When controlling for other covariates listed previously, vitamin D remained directly related to both isometric and isokinetic arm strength but only to isometric leg strength.
Conclusion: These data suggest that there may be a differential effect of vitamin D on upper and lower body strength. The mechanism for this difference remains unclear but could be related to differences in androgenic effects or to differences in vitamin D receptor expression. Our study supports a direct relation between vitamin D and muscle strength and suggests that vitamin D supplementation be evaluated to determine whether it is an effective therapy to preserve muscle strength in adults.