Heart Rate Variability Following Blood Flow Restriction Resistance Exercise In Young Men And Women

Blood flow restriction resistance exercise (BFR) has been found to stimulate the autonomic nervous system less than traditional resistance exercise (TRE) in men, but prior studies have not included women. PURPOSE: To compare the acute effects of BFR and TRE on heart rate variability (HRV) in a mixed sample of men and women, and to compare responses between sexes. METHODS: Twenty-five adults (M = 14, age: 23 ± 3 yrs, body mass: 81.0 ± 13.0 kg, height: 175 ± 9 cm; F = 11, age: 22 ± 3 yrs, body mass: 59.9 ± 6.8 kg, height: 163 ± 8 cm) participated in the study. Following 1 repetition maximum (1RM) testing, two randomized barbell back squat exercise visits ≥48 hrs apart were performed. The BFR visit consisted of 4 sets of 30, 15, 15, 15 repetitions at 30% 1RM with 60s rest intervals. The TRE exercise visit consisted of 4 sets of 10 repetitions at 70% 1RM with 60s rest intervals. Pre- and post-exercise resting electrocardiograms were analyzed in the frequency-domain to assess low frequency (LF) and high frequency (HF) power. RESULTS: Two-way repeated measures ANOVA found an interaction effect for LF HRV (pre-TRE 48.98 ± 17.71nu; post-TRE 80.39 ± 11.86nu; pre-BFR 49.06 ± 20.72nu; post-BFR 72.07 ± 14.76nu; time p < 0.001; condition p = 0.134; interaction p = 0.039), as well as HF HRV (pre-TRE 49.82 ± 16.92nu; post-TRE 19.72 ± 11.05nu; pre-BFR 49.68 ± 19.03nu; post-BFR 27.709 ± 14.30nu; time p < 0.001; condition p = 0.128; interaction p = 0.046). Bonferroni post hoc analysis showed only a significant increase in LF and decrease in HF HRV post-exercise in both conditions (each p < 0.05). Additional post hoc analysis examined the change from baseline and displayed attenuated changes in LF (TRE +30.90 ± 14.42∆nu; BFR +23.01 ± 18.82∆nu; p = 0.039) and HF HRV (TRE -29.67 ± 14.01∆nu; BFR -22.00 ± 18.15∆nu; p = 0.046) in BFR vs TRE. ANOVA testing comparing responses between men and women for ∆LF or ∆HF did not find an effect for sex (both p > 0.05), but ∆LF/HF responses were higher in men (M TRE +7.25 ± 8.35∆nu; W TRE +2.98 ± 1.84∆nu; M BFR +4.29 ± 6.27∆nu; W BFR +1.60 ± 2.02∆nu; sex p = 0.042, condition p = 0.237, interaction p = 0.661). CONCLUSION: Both TRE and BFR increased sympathetic activity (LF) and decreased parasympathetic activity (HF) indices of HRV, but the changes were attenuated for BFR. Men displayed greater ∆LF/HF responses than women regardless of resistance exercise type.