Abstract
BackgroundPrevious studies indicated that serum 25-hydroxyvitamin D [25(OH)D] concentrations are positively associated with physical activity levels independent of sun exposure. However, the effect of resistance training on serum 25(OH) D concentrations remains unclear. Thus, this study aimed to examine the effect of chronic resistance training on serum 25(OH) D concentrations and determine whether 25(OH) D concentration variations are influenced by body composition changes.MethodsEighteen young men aged 19–39 years were randomly divided into a 12-week resistance training group (RT, n = 9) and non-exercise control group (CON, n = 9). The trial was undertaken in Shanghai University of Sport in Shanghai, China. Randomization and allocation to trial group were carried out by a central computer system. Serum 25(OH) D and intact parathyroid hormone concentrations were measured using commercially available enzyme-linked immunosorbent assay kits. Body composition was measured by dual-energy X-ray absorptiometry.ResultsThe average serum 25(OH) D concentrations were 26.6 nmol/L at baseline. After the 12-week intervention program, serum 25(OH) D concentrations significantly increased in both groups. Serum 25(OH) D concentrations at midpoint (6-week) increased significantly only in the CON group (P < 0.01). From training midpoint to endpoint, a significantly greater increase in serum 25(OH) D concentrations was noted in the RT group (P-interaction = 0.043); 25(OH) D concentration changes (end-pre) were negatively related to fat-free mass (mid-pre) (r = − 0.565, P = 0.015) and muscle mass (mid-pre) (r = − 0.554, P = 0.017).ConclusionsThere were no beneficial effects of the 12-week resistance training on serum 25(OH) D concentration in vitamin D deficient young men, and an indication that seasonal increase in serum 25(OH) D concentrations during the early phase of resistance training was transiently inhibited, which may partly be attributed to resistance training-induced muscle mass gain.Trial registrationChinese Clinical Trial Registry, ChiCTR2000030876. Registered 16 March 2020 - Retrospectively registered, http://www.chictr.org.cn/showproj.aspx?proj=50504.
Highlights
Circulating 25-hydroxyvitamin D [25(OH)D] is the major form of vitamin D, which is used in vitamin D status assessment
The Fat-free mass (FFM) values and muscle mass significantly increased at the midpoint and endpoint compared to the baseline values, whereas no significant changes were observed in the control group (CON) group
In this study, we found that the seasonal increase in serum 25(OH) D concentrations in young men was transiently inhibited during the early phase of Resistance training (RT); subsequently, serum 25(OH) D concentrations increased in both RT and CON groups, and the increase was observed to be greater in RT group than in CON group
Summary
Circulating 25-hydroxyvitamin D [25(OH)D] is the major form of vitamin D, which is used in vitamin D status assessment. Scragg et al [5] found that higher levels of physical activity were associated with higher serum 25(OH) D concentrations during summer and during winter, when the vitamin D synthesis from sun exposure is extremely limited [11]. Several intervention studies suggested that endurance exercise could increase circulating 25(OH) D or prevent its seasonal reduction [12,13,14]. These findings indicated that physical activity could directly increase 25(OH) D concentrations. Previous studies indicated that serum 25-hydroxyvitamin D [25(OH)D] concentrations are positively associated with physical activity levels independent of sun exposure. This study aimed to examine the effect of chronic resistance training on serum 25(OH) D concentrations and determine whether 25(OH) D concentration variations are influenced by body composition changes
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