Abstract
This study determined if 6-weeks vitamin D2 supplementation (vitD2, 3800 IU/day) had an influence on muscle function, eccentric exercise-induced muscle damage (EIMD), and delayed onset of muscle soreness (DOMS) in National Association for Stock Car Auto Racing (NASCAR) NASCAR pit crew athletes. Subjects were randomized to vitD2 (n = 13) and placebo (n = 15), and ingested supplements (double-blind) for six weeks. Blood samples were collected and muscle function tests conducted pre- and post-study (leg-back and hand grip dynamometer strength tests, body weight bench press to exhaustion, vertical jump, 30-s Wingate test). Post-study, subjects engaged in 90 min eccentric-based exercise, with blood samples and DOMS ratings obtained immediately after and 1- and 2-days post-exercise. Six weeks vitD2 increased serum 25(OH)D2 456% and decreased 25(OH)D3 21% versus placebo (p < 0.001, p = 0.036, respectively), with no influence on muscle function test scores. The post-study eccentric exercise bout induced EIMD and DOMS, with higher muscle damage biomarkers measured in vitD2 compared to placebo (myoglobin 252%, 122% increase, respectively, p = 0.001; creatine phosphokinase 24 h post-exercise, 169%, 32%, p < 0.001), with no differences for DOMS. In summary, 6-weeks vitD2 (3800 IU/day) significantly increased 25(OH)D2 and decreased 25(OH)D3, had no effect on muscle function tests, and amplified muscle damage markers in NASCAR pit crew athletes following eccentric exercise.
Highlights
IntroductionVitamin D deficiency is defined as a serum 25-hydroxyvitamin D (25(OH)D) concentration of
Vitamin D deficiency is defined as a serum 25-hydroxyvitamin D (25(OH)D) concentration of20 ng/mL or less, with vitamin D insufficiency established as 21–29 ng/mL [1]
National Association for Stock Car Auto Racing (NASCAR) pit crew athletes (n = 30) from Hendrick Motorsports (Concord, North Carolina, NC, USA) were recruited and invited to join the study if they agreed to avoid: (1) food and supplement sources that were high in vitamin D; (2) large dose vitamin/mineral supplements; (3) anti-inflammatory medications; (4) tanning beds and prolonged sun exposure
Summary
Vitamin D deficiency is defined as a serum 25-hydroxyvitamin D (25(OH)D) concentration of. Recent evidence suggests that optimal vitamin D status, defined by estimated maximum parathyroid (PTH) suppression, occurs at 25(OH)D levels of 40 ng/mL and higher [2,3]. Epidemiologic studies of elderly individuals support direct associations between 25(OH)D levels and physical performance, with some support in randomized clinical trials, especially among vitamin D deficient adults [12,13,14,15,16]. Limited evidence suggests that treatment of vitamin D insufficient athletes may improve performance [20,21]. We hypothesized that 6-weeks supplementation with vitamin D (3800 IU/day) using vitamin D2 Portobello mushroom powder would improve muscle function and strength, and attenuate EIMD and DOMS in NASCAR pit crew athletes during their off-season in December and January
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