The purpose of this study was to evaluate the impact of fall season vitamin D3 supplementation on strength/power, body composition, and anabolic hormones in swimmers with optimal vitamin D status at summer's end. Male and female National Collegiate Athletic Association Division I swimmers (N = 19) with optimal 25-hydroxyvitamin D [25(OH)D] randomly received 5,000 IU of vitamin D3 (VITD) or placebo (PLA) daily for 12 weeks while participating in swimming and strength and conditioning training (August-November). Before and after the intervention, the participants underwent blood sampling for analysis of serum 25(OH)D, parathyroid hormone, total testosterone, free testosterone, sex hormone-binding globulin, and insulin-like growth factor 1, dual-energy X-ray absorptiometry, and strength/power testing (bench press, squat, dead lift, standing broad jump, vertical jump, and dips and pull-ups). Sex was used as a covariate for analyses. The 25(OH)D was decreased by 44% in PLA (p < .05) and increased by 8% in VITD over the 12 weeks. Fat-free mass increased in VITD (56.4-59.1 kg; p < .05), but not PLA (59.4-59.7 kg; p < .01). Significant Group × Time interaction effects were observed for dead lift (F = 21.577, p < .01) and vertical jump (F = 11.219, p < .01), but no other strength/power tests. Total testosterone decreased similarly in both groups, but free testosterone decreased and sex hormone-binding globulin increased only in PLA (p < .01). There were no group differences or changes in insulin-like growth factor 1 with the intervention. The findings suggest that vitamin D supplementation is an efficacious strategy to maintain 25(OH)D during the fall season training and to enhance some aspects of strength/power and fat-free mass in swimmers. Further research on the relationship between vitamin D and anabolic hormones is needed.

中文翻译：

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季节性维生素 D3 补充剂对大学游泳运动员力量、爆发力和身体成分的影响。

本研究的目的是评估秋季补充维生素 D3 对夏季结束时具有最佳维生素 D 状态的游泳者的力量/爆发力、身体成分和合成代谢激素的影响。具有最佳 25-羟基维生素 D [25(OH)D] 的男性和女性国家大学体育协会 I 组游泳运动员 (N = 19) 每天随机接受 5,000 IU 维生素 D3 (VITD) 或安慰剂 (PLA)，持续 12 周，同时参加游泳和体能训练（8 月至 11 月）。干预前后对参与者进行血样分析血清25(OH)D、甲状旁腺激素、总睾酮、游离睾酮、性激素结合球蛋白、胰岛素样生长因子1、双能X线片吸收测定法和力量/爆发力测试（卧推、深蹲、硬拉、立跳远、垂直跳、俯卧撑和引体向上）。性别被用作分析的协变量。在 12 周内，PLA 中的 25(OH)D 降低了 44% (p < .05)，而 VITD 中的 25(OH)D 增加了 8%。VITD 的无脂肪质量增加（56.4-59.1 kg；p < .05），但 PLA 没有增加（59.4-59.7 kg；p < .01）。对于硬拉 (F = 21.577, p < .01) 和垂直跳跃 (F = 11.219, p < .01)，观察到显着的组 × 时间交互效应，但没有其他力量/功率测试。两组的总睾酮下降相似，但游离睾酮下降，性激素结合球蛋白仅在 PLA 中增加（p < .01）。干预后胰岛素样生长因子 1 没有组间差异或变化。研究结果表明，补充维生素 D 是一种有效的策略，可在秋季训练期间维持 25(OH)D，并增强游泳者的力量/爆发力和无脂肪质量的某些方面。需要进一步研究维生素 D 和合成代谢激素之间的关系。