| Objective :Previous studies showed a positive correlation between physical activity and circulating vitamin D levels, and the relationship remained even after adjusting the effects of sun exposure. However, related researches are mostly observational study,which cannot draw the causal relationship. The few interventional researches studying the relationship between exercise and circulating vitamin D levels cannot obtain accurate conclusions due to the incomplete experimental design. Therefore, this study aimed to elucidate whether resistance exercise improves the circulating vitamin D levels using the randomized controlled trial design. The results would be useful to doctors and experts those are working on improving public health.Methods :In this study, 18 healthy men (19?39 yrs) were recruited in Yangpu District, Shanghai(31°27'N). They were randomly divided into exercise group (n=9, mean age=24.4yrs,mean BMI=22.9 kg/m ) and control group(n=9,mean age=26.7yrs,mean BMI=22.4 kg/m2). The exercise group took part in a 12 weeks resistance exercise, 3 times a week,and at the load intensity of 12-RM (repetition maximum), in addition, they were asked to maintain the previous living habits during the trial. The control group was asked to maintain the previous living habits and avoid deliberately change. Fasting blood samples and other related data was collected at baseline, seventh week and thirteenth week, respectively. Serum 25 hydroxyvitamin D[25 (OH) D], parathyroid hormone(iPTH) and insulin-like growth factor 1 (IGF-1) were measured by ELISA, and moderate and vigorous intensity physical activity(MVPA) was measured by three axes accelerometer Actigraph GT3X+.Muscle mass and body fat rate were measured by dual energy X-ray absorptiometry, and motion corresponding 1-RM was obtained by formula.Results :There was no significant difference between the exercise group and the control group at the baseline, and the serum 25(OH)D levels of all participants were vitamin D deficiency (exercise group: 27.8±2.0nmol/L; control group: 26.2±1.4nmol/L). After 12 weeks of resistance exercise, serum 25(OH)D concentration of exercise group and control group both increased significantly, and the main effect of time and the interaction between time and groups remained significant after adjusting the effect of sun exposure,MVPA,and body fat rate change (ptime=0.018, pinteraction =0.026). Till the seventh week, the change of exercise group in serum 25(OH)D leves was not significant (p=0.648), but the control group increased significantly (p<0.05),moreover, the interaction between groups and time was significant (p=0.026).Serum concentration of IGF-1 and iPTH of 2 groups did not change significantly, but the muscle mass significantly increased in the exercise group (p=0.002), while the control group had no significant change (p=1.0).During the last 6 weeks, the 2 groups' serum 25 (OH) D concentration increased significantly, and there was a significant main effect of time after adjusting the 3 confounding factors (p=0.009),but the interaction between time and the groups was not significant (p=0.274). The change of serum iPTH concentration and muscle mass in the 2 groups were not significant difference. However, the concentration of serum IGF-1 decreased significantly in the exercise group (p=0.013), and the control group had no significant change (p=1.0), moreover, the interaction between time and groups was significant after adjust the effect of age and MVP A (p=0.011). At the seventh week, 3 of 5 motions' 1-RM significantly increased, in addition, all motions' 1-RM significant increased during the last 6 weeks.Conclusions:First six weeks of resistance exercise weakened the increase of the serum 25(OH)D concentration in the vitamin D deficiency healthy men ,but the last six weeks resistance exercise had no effect. We suggest that the effects of resistance exercise on serum 25(OH)D concentration are different in different exercise stages. |
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