The effect of vitamin D supplementation on cardiorespiratory fitness and muscle strength in male adults undergoing basic military training.

BACKGROUND: Vitamin D deficiency (VDD) is ubiquitous in the Indian subcontinent. VDD has been shown to impair muscle functions. However, the association of VDD with cardiorespiratory endurance is uncertain. Hence, we enrolled and supplemented vitamin D in military recruits with VDD with an aim to evaluate effect of supplementation on cardiorespiratory endurance and muscle strength. METHOD: We enrolled 90 military recruits with VDD and randomly allotted them to two groups equally. The group I received cholecalciferol granules 60,000 IU every fortnight for twelve weeks (cases), and the group II was observed as control. Muscle strength and cardiorespiratory endurance was assessed with a battery of tests (standing broad jump, bent arm hang test, 20 m shuttle run) at baseline and repeated at the end of training (nineteen weeks). Blood samples were collected for measurement of serum 25(OH)D and parathyroid hormone. RESULTS: In Group I and Group II, there was significant increase in 25(OH) D levels (25.8 ± 7.1 and 17.3 ± 3.5 ng/ml, respectively), and in VO2 max (9.8 ± 8.8 and 12.7 ± 8.6 ml/kg/min, respectively) compared with the baseline values. However, no significant change was observed in muscle strength after supplementation. There was no difference between the groups in VO2 max and muscle strength at baseline and at the end of training. CONCLUSION: Vitamin D supplementation did not improve muscle strength and cardiorespiratory endurance in military recruits with VDD. A significant rise in 25(OH) D was observed even in those not supplemented with vitamin D.