Changes in Heart Rate Variability and Fatigue Measures Following Moderate Load Resistance Exercise

The purpose of this study was to determine the relationship between changes in heart rate variability (HRV), neuromuscular performance, and fatigue biomarkers in response to a resistance exercise bout. The root mean square of successive RR interval differences (RMSSD), neuromuscular performance - isometric handgrip (IHG), countermovement jump (CMJ), mean propulsive velocity (MPV) - metabolic stress (lactate [Lac]) and inflammation (interleukin-6 [IL-6]) were measured in 30 subjects who performed 6×10 back squat (BS), 3×10 bench press (BP), and 3×10 bent-over rows (BR) at 70% of 1-repetition maximum (1RM). The RMSSD, neuromuscular performance, and biomarkers were measured 10 min pre-exercise and 30 min post-exercise (Post₃₀); HRV and Lac were also measured immediately post-exercise (Post₀). Pre- versus post-exercise differences were evaluated using paired-samples t-tests. Pearson's correlations were used to determine the association between changes. With the exception of IL-6 (P=0.296) and MPV_BP (P=0.678), LnRMSSD, neuromuscular performance, and metabolic stress were different post- compared to pre-exercise. We observed moderate associations between ΔLnRMSSD Post₀ and ΔLac Post₀ (r = -0.44) and ΔLac Post₃₀ (r = -0.55), respectively. Practitioners should use multiple training load indicators to gain an accurate depiction of recovery.