Vitamin D, Muscle Strength and Cardiorespiratory Fitness – An Evidence-based Review

Recent evidence reported that a higher concentration of 25-hydroxyvitamin D [25[OH] D] has been associated with greater cardiorespiratory fitness [CRF] and muscle strength in both sexes. Low levels of 25[OH]D may be related to hypertrophy of myocardial, high blood pressure, and endothelial dysfunction, which is related to decreased amino acid uptake, prolonged time to peak muscle contraction and relaxation, dysregulation of intracellular Ca2+, muscle weakness, myalgia, impaired neuromuscular function, and hypotonia. Because CRF is defined as a function of maximal cardiac output and maximal arteriovenous oxygen difference, low levels of 25[OH]D may lead to deleterious effects on CRF. Recent findings also indicated vitamin D3 supplementation that leads to an increase in muscle fiber especially type 2, the cross-sectional area of muscle fibers, and improved muscle strength. In this chapter, we will systematically review the observational studies and randomized controlled trials that evaluated the association of vitamin D with CRF and muscle strength.