Rest period between sets is one of most important training factors that effects on effectiveness of resistance training; however, there is a little information about the effect of rest period length on muscular hypertrophy. The purpose of present study was to comparison the effect of very short vs. short rest period between the sets in resistance training on hormonal adaptations and thigh muscles hypertrophy.
Twenty healthy young women (20-35 years of old) volunteered to participate in this study as the subject. Subjects were randomly assigned to either a very short (30 second; P30) or short (120 second; P120) rest period group. During the first 2 weeks of training, 3 sets of 10-12 repetition maximum (RM) with 120 second rest intervals between sets and exercises (hamstring with machine, squat, dead lift and leg press) were performed by both groups. During the next 6 weeks of training, the P120 group trained using 120 second between sets and exercises (4 sets of 8-10RM), and the P30 group trained using 30 second between sets and exercises as the 6 weeks of training progressed (4 sets of 8-10RM). 2 × 3 repeated measures ANOVA was used to evaluate time-course change in variables. Post hoc analyses (Bonferroni) were then performed when warranted and the level of significance in all statistical analyses was set at P≤0.05.
The results indicated that quadriceps cross-sectional area (CSA), hamstring CSA and total thigh muscle CSA increased after both of resistance training (P<0.05) but no significant differences were observed between these training. For testosterone (Ts) no significant change was observed and growth hormone (GH) level was increased in P30 and P120 groups and decreased to baseline level 30 min after the training. Cortisol (Cor) concentration decreased (P<0.05) and insulin growth factor-1 (IGF-1) and Ts/Cor ratio increased (P<0.05) only in P120 group and these changes were continued 30 min after the training.
Attention to our results, it suggests that 120 second rest between sets for thigh muscle hypertrophy and more anabolic hormones secretion in women.