Recovery from sauna bathing favorably modulates cardiac autonomic nervous system

Abstract Objective Sauna bathing is becoming a common activity in many countries and it has been linked to favorable health outcomes. However, there is limited data on the heart rate (HR) and heart rate variability (HRV) responses to an acute sauna exposure. Design We conducted a single-group, time series longitudinal study utilizing a pre-post design to examine acute effects of sauna bathing on the autonomic nervous system as reflected by HRV. A total of 93 participants (mean [SD] age: 52.0 [8.8] years, 53.8% males) with cardiovascular risk factors were exposed to a single sauna session (duration: 30 minutes; temperature: 73 °C; humidity: 10-20%) and data on HRV variables were collected before, during and after sauna. Results Time and frequency-domain HRV variables were significantly modified (p  Conclusions This study demonstrates that a session of sauna bathing induces an increase in heart rate. During the cooling down period from sauna bathing, HRV increased which indicates the dominant role of parasympathetic activity and decreased sympathetic activity of cardiac autonomic nervous system. Future randomized controlled studies are needed to show if HR and HRV changes underpins the long-term cardiovascular effects induced by regular sauna bathing.