CONCLUSIONS Vitamin D supplementation positively affected lower limb muscle strength in athletes , but not upper limb muscle strength or muscle power .
Different muscle groups and functions may respond differently to vitamin D supplementation .
BACKGROUND Vitamin D may play a role in skeletal muscle because of the discovery of VDR in skeletal muscle .
However , vitamin D deficiency is a global problem , including athletes .
Studies examining the effect of vitamin D supplementation on muscle function in athletes have inconsistent results .
Therefore , we aim ed to quantitatively summarize the evidence for the effect of vitamin D supplementation on skeletal muscle strength and explosive power of athletes using a meta- analysis .
Vitamin D3 Supplementation Does Not Improve Sprint Performance in Professional Rugby Players: A Randomized, Placebo-Controlled, Double-Blind Intervention Study.
Vitamin D insufficiency is common in athletes and may lower physical performance . Many cross-sectional studies associate vitamin D status with physical performance in athletes ; however , there have been few prospect i ve r and omized controlled trials with adequate statistical power to test this relationship , and none in the southern hemisphere . Thus , a prospect i ve double-blind , r and omized , placebo-controlled intervention trial was conducted involving 57 professional rugby union players in New Zeal and . Participants were r and omized to receive 50,000 IU of cholecalciferol ( equivalent to 3,570 IU/day ) or placebo once every two weeks over 11 - 12 weeks . Serum 25(OH)D concentrations and physical performance were measured at baseline , weeks 5 - 6 , and weeks 11 - 12 . Mean ( SD ) serum 25(OH)D concentrations for all participants at baseline was 94 ( 18 ) nmol/L , with all players above 50 nmol/L. Vitamin D supplementation significantly increased serum 25(OH)D concentrations compared to placebo , with a 32 nmol/L difference between groups at 11 - 12 weeks ( 95 % CI , 26 - 38 ; p < 0.001 ) . Performance in five of the six tests at study completion , including the primary outcome variable of 30-m sprint time , did not differ between the vitamin D supplemented and placebo groups ( p > 0.05 ) . Performance on the weighted reverse-grip chin up was significantly higher in players receiving vitamin D compared with placebo , by 5.5 kg ( 95 % CI , 2.0 - 8.9 ; p = 0.002 ) . Despite significantly improving vitamin D status in these professional rugby union players , vitamin D supplementation had little impact on physical performance outcomes . Thus , it is unlikely that vitamin D supplementation is an ergogenic aid in this group of athletes
CONCLUSIONS Vitamin D supplementation positively affected lower limb muscle strength in athletes , but not upper limb muscle strength or muscle power .
Different muscle groups and functions may respond differently to vitamin D supplementation .
BACKGROUND Vitamin D may play a role in skeletal muscle because of the discovery of VDR in skeletal muscle .
However , vitamin D deficiency is a global problem , including athletes .
Studies examining the effect of vitamin D supplementation on muscle function in athletes have inconsistent results .
Therefore , we aim ed to quantitatively summarize the evidence for the effect of vitamin D supplementation on skeletal muscle strength and explosive power of athletes using a meta- analysis .