Heart rate variability-guided training in professional runners: Effects on performance and vagal modulation

•HRV-guided training allows profesional runners to achieve higher training intensities.•This is reflected in their cardiovascular performance and HRV enhancement.•The increment in HRV scores suggest better cardiovascular adaptations.•A polarized training is recommended to improve performance and vagal modulation. Purpose: To analyze the training structure following a heart rate variability (HRV) -guided training or traditional training protocol, determining their effects on the cardiovascular performance of professional endurance runners, and describing the vagal modulation interaction. Methods: This was an 8-week cluster-randomized controlled trial. Twelve professional endurance runners were randomly assigned to an HRV-guided training group (HRV-G; n = 6) or a traditional training group (TRAD-G; n = 6). The training methodology followed by the HRV-G was determined by their daily HRV scores. Training intensities were recorded daily. HRV4Training was used to register the rMSSD every morning and during a 60-second period. Cardiovascular outcomes were obtained through an incremental treadmill test. The primary outcome was the maximal oxygen uptake (VO2max). Results: Total training volume was significantly higher in TRAD-G, but moderate intensity training was significantly higher in HRV-G (X ± SDDif=1.98 ± 0.1%; P = 0.006; d = 1.22) and low intensity training in TRAD-G (X ± SDDif=2.03 ± 0.74%; P = 0.004; d = 1.36). The maximal velocity increased significantly in HRV-G (P = 0.027, d = 0.66), while the respiratory exchange ratio increased in TRAD-G (P = 0.017, d = 1). There was a small effect on the LnRMSSD increment (P = 0.365, d = 0.4) in HRV-G. There were statistical inter-group differences in the ∆maximal heart rate when ∆LnrMSSD was considered as a covariable (F = 7.58; P = 0.025; d = 0.487). There were significant and indirect correlations of LnRMSSDTEST with VO2max (r =-0.656, P = 0.02), ∆LnrMSSD with ∆VO2max (r = -0.606, P = 0.037), and ∆LnrMSSDCV with ∆VENT (r = -0.790, P = 0.002). Conclusions: higher HRV scores suggest better cardiovascular adaptations due to higher training intensities, favoring HRV as a measure to optimize individualized training in professional runners.