PURPOSE: The purpose of this study was to examine the acute hormonal responses of three different rest periods between sets of a traditional lower body resistance training session in young women. METHODS: Twelve apparently healthy, trained females (26.83± 3.93 yrs) participated in the study protocol. On three separate sessions of a lower body resistance exercise protocol, subjects were randomly assigned a rest interval of either 30 (P30), 60 (P60) or 120 (P120) seconds between sets. The resistance exercise session consisted of four lower body exercises (bilateral knee extension, bilateral knee flexion, leg press, and squat) with 3 sets of 10 repetitions at 10-repetition maximum (RM) load. Blood samples were drawn for determination of serum growth hormone (GH) concentrations before exercise (T0), immediately after each training session (T1), and 5 (T5), 15 (T15), and 30 (T30) minutes of recovery. Statistical evaluation of the data was measured using a 3 x 5 repeated measurements analysis of variance [rest interval (30, 60, and 120 s) x time (T0, T1, T5, T15, T30)] with a least-significant difference (LSD) post-hoc procedure for all hormonal measurements. The probability level of statistical significance was set at p < 0.05 in all comparisons. RESULTS: There were no differences among protocols (P30, P60 and P120) in the serum GH concentrations at baseline (T0). However, as compared to T0, all protocols led to acute increases (p < 0.05) in serum GH concentrations after each training session. The GH concentrations between protocols were significantly higher for P30 (24.34 ng/ml) and P60 (23.07 ng/ml) as compared to P120 (17.13 ng/ml) at T1. The P30 GH concentrations were significantly higher at T5, T15, and T30 as compared to P60 and P120. CONCLUSION: The magnitude of acute hormonal (GH) responses in previously strength-trained women seems to be greater with a 30-second rest interval between sets compared to longer rest periods (60s or 120s).
resistance exercise; GH; rest interval
