3.3.1. Effects of HMB supplementation on serum cortisol concentration
Overall, HMB consumption had no significant effect on cortisol concentration: WMD= -1.35 μg/dl; 95% CI: -2.70, 0.002; P= 0.050. There was no significant heterogeneity among the studies (Cochran’s Q test = 14.05, P= 0.050, I2=50.2%). Subgroup analyses of different types of exercise showed that cortisol concentration significantly reduced after resistance exercises (WMD= -3.30 μg/dl; 95% CI: -5.50, -1.10; P= 0.003), whereas it had not significant effect on cortisol concentration in aerobic and anaerobic combined activities (WMD= -0.16; 95% CI: -1.16, 0.84; P= 0.753). The results of subgroup analysis are shown in Table 3 and the forest plot is shown inFigure 2 .