Recovery Of Heart Rate Variability And Hemodynamics After Heated Exercise In Active Females

Abstract

Previous research has demonstrated that men who exercise in heat have challenged autonomic recovery, though little research has been conducted in females. PURPOSE: The purpose of this study was to assess the recovery of autonomic function in women who performed moderate-intensity exercise in heat. METHODS: Seven women (31.7± 7.6 years, 67.3±4.1 kg, 25.7±5.6 % Fat, 43.9±5.1 mL/kg/min) completed two identical bouts of graded treadmill walking (~60% VO2peak). One bout was hot (35-40°C, > 40% relative humidity (RH)), and the other served as a control (18-22°C, < 40% RH). For 24 h before and after each bout, participants had heart rate variability (HRV), specifically RMSSD, monitored. After each exercise bout, HR and BP were monitored during 30 min of supine recovery and 10 min of orthostatic tolerance assessment. RESULTS: RMSSD was more suppressed following exercise in the heat and remained lower than in the control condition for one hour (p < 0.05). During supine recovery, heat exposure led to higher HR (p = 0.002) and lower DBP (p = 0.016). SBP (p = 0.037) and DBP (p = 0.008) were both lower after 10 min of supine recovery following hot exercise than after control temperature. Average response did not reveal orthostatic hypotension despite heat causing a higher HR (p = 0.011) and lower SBP (p =0.026) after 10 min of orthostatic exposure. CONCLUSIONS: Exercise in heat causes greater disruptions in cardiovascular autonomic functioning for at least one hour after exercise. Women who exercise in heat should be wary of an exacerbated HR response following exercise in the heat and low recovery blood pressures with associated symptoms.