Background The beneficial adaptation of skeletal muscle function to strenuous exercise is partially attributable to the improvement of vitamin D status. The present study aimed to evaluate the effects of a 3-week vitamin D supplementation on serum 25(OH)D levels and skeletal muscle biomarkers (i.e. troponin, myoglobin, creatine kinase and lactic dehydrogenase) of endurance runners. Methods A double-blind placebo-controlled study design was used and vitamin D supplementation was compared to a non-treatment control group. Twenty-four runners, competitors of the ultra-marathons held during the National Running Championships, were randomly assigned into two groups supplemented with the dose of 2000 IU vitamin D or placebo for three weeks. All subjects participated in three exercise protocols: (a) incremental exercise test (to determine the maximum oxygen uptake and the intensity of eccentric exercise), (b) eccentric exercise before and (c) after two dietary protocols. Venous blood samples were drawn at rest, immediately after the exercise and after 1 h and 24 h of recovery in order to estimate serum 25(OH)D levels, skeletal muscle biomarkers, proinflammatory cytokines and tumor necrosis factor-alpha (TNF-α) levels. A two-way ANOVA was used to test main effects and their interactions and Pearson correlation coefficients were analyzed to determine the effects of inter-variable relationships. Results Significant differences between pre- and post-intervention in baseline 25(OH)D levels were observed (34.9 ± 4.7 versus 40.3 ± 4.9 ng/ml , p = 0.02) in supplemented group. A higher post intervention 25(OH)D level was observed after vitamin D diet compared to placebo (40.3 ± 4.9 versus 31.8 ± 4.2 ng/mL, respectively; p < 0.05). The vitamin D supplementation decreased post-exercise (TN max) and 1 h post-exercise troponin ( p = 0.004 , p = 0.03, respectively), 1 h post-exercise myoglobin concentration ( p = 0.01) and TNF-α levels( p < 0.03). 24 h post exercise creatine kinase activity was significantly lower in supplemented group compared to placebo (p < 0.05). A negative correlation was observed between post exercise 25(OH)D levels and myoglobin levels ( r = − 0.57 ; p = 0.05), and 25(OH)D levels and TNFα (r = − 0.58; p = 0.05) in vitamin D supplemented group. Conclusions Three weeks of vitamin D supplementation had a positive effect on serum 25(OH)D levels in endurance trained runners and it caused a marked decrease in post-exercise biomarkers levels. We concluded that vitamin D supplementation might play an important role in prevention of skeletal muscle injuries following exercise with eccentric muscle contraction in athletes.

中文翻译：

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补充维生素D对跑步者血清总25(OH)水平及骨骼肌生化指标的影响

背景 骨骼肌功能对剧烈运动的有益适应部分归因于维生素 D 状态的改善。本研究旨在评估补充维生素 D 3 周对耐力跑者血清 25(OH)D 水平和骨骼肌生物标志物（即肌钙蛋白、肌红蛋白、肌酸激酶和乳酸脱氢酶）的影响。方法 采用双盲安慰剂对照研究设计，并将维生素 D 补充剂与非治疗对照组进行比较。在全国跑步锦标赛期间参加超级马拉松比赛的 24 名跑步者被随机分配到两组，分别补充 2000 IU 维生素 D 或安慰剂三周。所有受试者都参加了三种锻炼方案：（a）增量运动测试（确定最大摄氧量和离心运动强度），（b）在两种饮食方案之前和（c）之后的离心运动。在休息时、运动后立即以及恢复 1 小时和 24 小时后抽取静脉血样本，以估计血清 25(OH)D 水平、骨骼肌生物标志物、促炎细胞因子和肿瘤坏死因子-α (TNF-α)水平。使用双向方差分析来测试主效应，并分析它们的相互作用和 Pearson 相关系数以确定变量间关系的影响。结果 在补充组中观察到干预前和干预后基线 25(OH)D 水平的显着差异（34.9 ± 4.7 对 40.3 ± 4.9 ng/ml，p = 0.02）。与安慰剂相比，维生素 D 饮食后观察到更高的干预后 25(OH)D 水平（分别为 40.3 ± 4.9 和 31.8 ± 4.2 ng/mL；p < 0.05）。补充维生素 D 降低运动后（TN max）和运动后 1 小时肌钙蛋白（分别为 p = 0.004 和 p = 0.03）、运动后 1 小时肌红蛋白浓度（ p = 0.01）和 TNF-α 水平（ p < 0.03)。与安慰剂组相比，运动后 24 小时的肌酸激酶活性在补充组中显着降低（p < 0.05）。观察到运动后 25(OH)D 水平与肌红蛋白水平 (r = − 0.57; p = 0.05) 以及 25(OH)D 水平与维生素 D 中的 TNFα (r = − 0.58; p = 0.05) 呈负相关补充组。结论三周的维生素 D 补充剂对耐力训练跑步者的血清 25(OH)D 水平产生积极影响，并导致运动后生物标志物水平显着下降。我们得出的结论是，补充维生素 D 可能在预防运动员离心肌肉收缩运动后的骨骼肌损伤方面发挥重要作用。