Heart Rate Variability, Blood Pressure Variability, and Baroreflex Sensitivity in Overtrained Athletes

Objective: To assess the effects of abruptly intensified physical training on cardiovascular control. Design: Retrospective longitudinal study in a research laboratory. Participants: Ten healthy athletes (5 men, 5 women) from track and field and triathlon. Interventions: A 2-week training camp with daily stepwise increasing cycling tests, 40 minutes of running, and additional 60 minutes of cycling. Main Outcome Measurements: Time and frequency domain parameters of resting heart rate variability (HRV), blood pressure variability (BPV), and baroreflex sensitivity (BRS) before (M1), during (M2), and after (M3) the training camp. Results: HRV was significantly reduced during training (meanNN: 1042 [937–1194] ms vs 933 [832–1103] ms vs 1055 [947–1183] ms, P<0.01; rmssd: 68 [52–95] ms vs 52 [38–71] ms vs 61 [48–78] ms, P<0.05). BRS was significantly reduced (25.2 [20.4–40.4] vs 17.0 [12.9–25.7] vs 25.7 [18.8–29.1] ms/mmHg, P<0.05). These effects largely disappeared after 3–4 days of recovery. Conclusion: Abruptly intensified training shifts autonomic cardiovascular activity toward parasympathetic inhibition and sympathetic activation; HRV and BRS monitoring may provide useful markers to detect and avoid overtraining.