Background: A growing body of research is raising concern regarding the prevalence of poor vitamin D status among athletes. Besides it’s well known association with low bone mineral density, an addition sign of vitamin D deficiency is muscular weakness and soreness, suggesting that deficiency in athletic populations may inhibit optimal physical performance and increase the risk of injury. It is difficult to achieve optimal vitamin D status through diet alone, so it is important to assess all sources of vitamin D, including dietary intake, supplementation, and amount and frequency of sun exposure to obtain a comprehensive profile of vitamin D risk. Currently, there are no studies that include such a complete profile of vitamin D risk in collegiate football players.

Purpose: The purpose of this study is to investigate the associations between sun exposure and diet, as markers of vitamin D status, and training-induced muscle soreness in collegiate football players. More specifically, this study assesses if total sun exposure and dietary vitamin D intake are related to muscle soreness.

Methods: Twenty-four male collegiate football players were recruited for this cross-sectional study in October 2015. Player body composition was measured using a multi-current bioelectrical impedance analyzer (BIA). Dietary intake, sun exposure, and muscle soreness data were collected via interview. The Sun Exposure Questionnaire and the Short Form McGill Pain Questionnaire (SF-MPQ) were used to assess weekly sun exposure and muscle soreness, respectively.

Results: The mean vitamin D intake (10.8±9.5 mcg) was below the RDA for vitamin D (15 mcg), with only 7 participants (29.2%) meeting or exceeding the RDA. Dietary vitamin D intake was inversely associated with portion of muscle sore (r_s = -0.393, p = 0.029). SF-MPQ total and affective scores were each inversely associated with weekly time outdoors (r_s = -0.362, p = 0.041; r_s = -0.449, p = 0.014, respectively). T-test analysis found that the mean SF-MPQ affective pain score was significantly lower for players with a time outdoors score above the mean (p = 0.04).

Conclusion: There is a high prevalence of insufficient dietary vitamin D intake (70.8%) identified in a collegiate football team. Our findings suggest that higher dietary vitamin D intake and more time spent outdoors are associated with a lower proportion of muscular soreness and decreased perceived pain. Thus, achieving a satisfactory vitamin D status, through a combination of diet and sun exposure, may reduce vitamin D deficiency associated risks, including lowering muscle soreness, thereby serving to enhance athletic performance.