The effect of vitamin D status on various measures of physical performance of collegiate-age athletes
Joyce, Donald A.
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Purpose: Vitamin D is a concern for individuals who live at higher latitudes due to seasonality of sun exposure and intensity. Previous studies have shown that poor vitamin D status is associated with muscle weakness in test animals and the elderly. Supplementation has been shown to reverse vitamin D associated muscle weakness. Studies suggest that athletes are at risk of developing poor vitamin D status and thus may be at risk of skeletal muscle weakness. Hypothesis: We believe that Vitamin D supplementation will improve physical performance in healthy, college-age athletes that have poor vitamin D status. Methods: 25 subjects from the Buffalo, NY area were screened for cardiovascular disease risk and entry requirements (Serum 25(OH) Vitamin D between 10-30ng/mL and VO2max in the upper 50 th percentile). 13 subjects were enrolled in a double blind, placebo controlled parallel arm design with 4 visits. Each test visits consisted of Vertical Jump, Wingate, 3RM Bench Press, and 5x6sec Repeated Sprint tests. After visit 2, subjects received either a 60,000IU dose of vitamin D (n=7) or placebo (n=6). Serum vitamin D and calcium were measured throughout for safety. Results: 12 subjects completed all of the visits (1 subject withdrew due to scheduling conflicts). Vitamin D status rose in significantly in the test group (9ng/mL), while the control group saw no significant change. A Two Way Repeated Measures ANOVA showed that there was no effect after supplementation on any of the measures of physical performance (p>0.05). Conclusion: Our findings suggest that there may be no effect of vitamin D on skeletal muscle function in young, healthy individuals.