The Effect of Vitamin D Supplementation in Elite Adolescent Dancers on Muscle Function and Injury Incidence: A Randomised Double-Blind Study.

PURPOSE: A number of studies have noted low levels of Vitamin D in dancers and this has been associated with increased risk of injuries and decreased muscular strength indices. The aim of the present study was to examine whether vitamin D supplementation over a 4-month period can improve muscle function and injury incidence.

METHODS: Eighty-four participants volunteered, exclusion criteria and drop out (19%) reduced cohort to 67 (f=29, m=38; 17-19yrs). Participants were randomly assigned to either an intervention or placebo group (2:1 ratio). All provided a venous blood sample pre and post the 4-month study period. The intervention group received 120,000IU vitamin D to be taken over a 1-week period and the placebo group received the same number of inert pills. Participants completed a series of muscle function tests pre and post the monitoring period. Injury incidence was recorded by the independent health team at the school.

RESULTS: Pre-intervention 6% of the cohort were vitamin D deficient, 81% were insufficient and 13% had sufficient levels; post-intervention 53% were insufficient and 47% were sufficient. The intervention group reported a significant increase in serum 25(OH)D3 (57%; p<0.00) and isometric strength (7.8%; p=0.022) but not muscular power. There was a significant association between traumatic injury occurrence for the intervention and control groups (10.9% vs. 31.8%; p < .02).

CONCLUSION: Vitamin D supplementation decreased the numbers of deficient and insufficient participants within this cohort. The intervention group reported a small significant increase in muscle strength that was negatively associated with traumatic injury occurrence.