Title screen

[References: 77 tit.)]

Purpose This study investigated the effects of acute hypoxic exposure on post-exercise cardiac autonomic modulation following maximal cardiopulmonary exercise testing (CPET). Methods Thirteen healthy men performed CPET and recovery in normoxia (N) and normobaric hypoxia (H) (FiO2=13.4%, 3500 m). Post-exercise cardiac autonomic modulation was assessed during recovery (300 s) through the analysis of fastphase and slow-phase heart rate recovery (HRR) and heart rate variability (HRV) indices. Results Both short-term, T30 (mean difference (MD) 60.0 s, 95% CI 18.2-101.8, p=0.009, ES 1.01), and long-term, HRRt (MD 21.7 s, 95% CI 4.1-39.3, p=0.020, ES 0.64), time constants of HRR were higher in H. Fast-phase (30 and 60 s) and slow-phase (300 s) HRR indices were reduced in H either when expressed in bpm or in percentage of HRpeak (p0.05). Conclusions Affected fast-phase, slow-phase HRR and HRV indices suggested delayed parasympathetic reactivation and sympathetic withdrawal after maximal exercise in hypoxia. However, a similar cardiac autonomic recovery was re-established within 5 min after exercise cessation. These findings have several implications in cardiac autonomic recovery interpretation and in HR assessment in response to high-intensity hypoxic exercise.