Acute Resistance Exercise Effects on Autonomic Modulation Between Resistance-Trained Men and Women

Abstract

While it has been reported that women have greater vagal withdrawal during aerobic exercise and supramaximal exercise compared to men, the sex-specific responses to an acute bout of resistance exercise are unknown. PURPOSE: To determine the effects of an acute bout of free-weight resistance exercise consisting of the squat, bench press, and deadlift on heart rate variability (HRV) and heart rate complexity (HRC) between the sexes. METHODS: Twenty-three resistance-trained (aged 23±3 yrs; mean±SD) men (n=13) and women (n=10) with a minimum of 1 year of resistance training volunteered for the study. Autonomic modulation was assessed at rest as well as 15-20 minutes (Rec1) and 25-30 minutes (Rec2) after an acute bout of resistance exercise utilizing 3 sets of 10 repetitions at 75% 1-repetition maximum on the squat, bench press and deadlift. Two minutes of rest was given between sets and exercises. A quiet control condition of the same duration was also utilized for each participant. Measures of HRV were analyzed in the frequency domain and included measures of vagal modulation (normalized high frequency (HFnu)), sympathetic modulation (normalized low frequency (LFnu)), and sympathovagal balance (LF/HF ratio). Sample Entropy (SampEn), indicative of vagal modulation, was used as a measure of HRC. A repeated measures ANOVA was used to compare the effects of sex (men and women) across the two conditions (resistance exercise and control) and time (rest, Rec1 and Rec2). T-tests were used for post-hoc testing if the ANOVA was significant with a Benjamini-Hochberg correction factor. RESULTS: There were no significant sex differences at rest for any of the variables. Furthermore, there were no significant sex x condition x time interactions for any variable. Compared with Rest LFnu (Rest: 35.5±15.3%; Rec1: 73.0±18.0; Rec2: 66.0±25.1%, p=0.0001), LnLF/HF (Rest: 4.0±0.9%; Rec1: 5.1±1.1%; Rec2: 5.2±1.1%, p=0.002) were augmented at Rec1 and Rec2. HFnu (Rest: 61.2±17.1%; Rec1: 40.3±22.3%; Rec2: 38.4±21.8%, p=0.0001) and SampEn (Rest: 1.5±0.3units; Rec1: 1.2±0.3units; Rec2: 1.3±0.5units, p=0.0001) were decreased at Rec1 and Rec2 compared to Rest after the acute resistance exercise. CONCLUSIONS: These data suggest that acute RE using free-weights has a profound impact on autonomic modulation that is similar between the sexes.