Effects of Rest Duration Between Sets of Resistance Training on Hormonal Responses in Young Women

Abstract

PURPOSE: The purpose of this study was to examine the acute hormonal response to three different rest periods between sets of a traditional lower body resistance training session in young women. METHODS: Twelve apparently healthy, resistance 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 assigned in a random order 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) and cortisol 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 × 5 repeated measures analysis of variance [rest interval (30, 60, and 120 s) × time (T0, T1, T5, T15, T30)]. The probability level of statistical significance was set at p < 0.05 in all comparisons. RESULTS: There were no differences between protocols (P30, P60 and P120) in the serum GH and cortisol concentrations at baseline (T0). However, as compared to T0, all protocols led to acute increases (p < 0.05) in serum GH and cortisol 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, T1 5, and T30 as compared to P60 and P120. The cortisol concentrations were significantly higher in P30 at T15 (452.02 nmol/L) and T30 (449.72 nmol/L) as compared to P60 (367.64 for T15, and 354.99 nmol/L for T30) andP120 (363.73 nmol/L for T15, and 346.02 nmol/L for T30). CONCLUSIONS: Exercise-induced metabolic stress is associated with acute GH and cortisol responses following a typical hypertrophic resistance training session. The magnitude of acute hormonal responses in previously strength-trained women appears greater with a 30-second rest interval between sets compared to longer rest periods of 60- or 120-seconds.