A single injection of vitamin D3 improves insulin sensitivity and beta cell function but not muscle damage or the inflammatory and cardiovascular responses to an acute bout of resistance exercise in vitamin-D deficient resistance-trained males.

Vitamin-D deficiency is now recognized problem affecting multiple physiological functions. The aim of this study was to evaluate the effect of a single dose of vitamin D3injection on the inflammatory, muscular damage, metabolic and cardiovascular responses to an acute bout of resistance exercise (RE)in vitamin D-deficient resistance-trained males.Blood samples from 14 vitamin D-deficient resistance-trained males were obtained during two separate trials: lower vitamin-D (LVD) and higher vitamin-D (HVD, after vitamin D3injection). Metabolic, inflammatory, muscle damage and cardiovascular markers were evaluated at baseline, immediately and 1-hour after RE. There were significant trial-by-time interactions for insulin and Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) which significantly (P ˂ 0.05) declined for 1-hour after RE in the HVD compared to LVD trial. Homeostasis Model Assessment of β-Cell Function (HOMA-ß) decline at 1-hour post-RE in the HVD trial. There was also a time-effect for blood sugar which significantly (P ˂ 0.05) decreased and for creatinekinase,lactate dehydrogenaseas well as interleukin 6 (IL-6) which increased significantly 1-hour post-RE in both trials. There were no significant changes in other inflammatory and cardiovascular markersfollowing both trials. A single injection of vitamin D3improved insulin-resistance and beta cell function following RE in previously vitamin D-deficient resistance-trained males. Conversely, the injection did not change muscle damage and the inflammatory response to acute RE.Intramuscular vitamin D replacement in vitamin D-deficient resistance-trained males may have key implications for the promotionof glucose metabolism and lowering the risk of diabetes in this population.