Heart rate variability and baroreceptor sensitivity following exercise-induced hyperthermia in endurance trained men

Abstract

We evaluated the effect of exercise-induced hyperthermia (EIH) on autonomic nervous system (ANS) function in the early (<80 min) and late (24 and 48 h) stages of recovery. Eight males underwent three repeated 6 min 70° head-up tilts (HUT1, HUT2 and HUT3), each separated by 10-min supine rest in a non-exercise/non-heat stress control state (NHS). On a separate day, three 6 min 70° HUT were performed following EIH (esophageal temperature ≥ 40°C) and repeated after 24 and 48 h of recovery. Heart rate, stroke volume (SV), mean arterial pressure and cardiac output ([Formula: see text]) were evaluated during the last min prior to a change in posture. Responses to 70° HUT were compared to the same challenge performed without prior exercise and under a NHS condition. Relative to NHS, [Formula: see text] was maintained during the repeated HUT's following EIH, despite significant reductions in SV and sustained elevations in esophageal temperature (p < 0.05). The preserved [Formula: see text] appears to be due to increased HR (HUT1: NRS = 76 ± 3 beats min(-1), EIH = 126 ± 6 beats min(-1)) stemming from modulation of the ANS toward sympathetic dominance. Parasympathetic withdrawal was evidenced by a reduction in root mean squared successive difference (i.e., HUT1: NHS = 66 ± 12 ms, EIH = 9 ± 1 ms) of heart rate variability and paralleled by a reduction in baroreceptor sensitivity for all HUT's following EIH (p < 0.05). Despite significant modulation in ANS activity, Q is maintained and participants do not become orthostatic intolerant/syncopal during the short-term recovery period following EIH. Normal ANS and cardiovascular function is restored following 24 h of recovery.

Heart rate variability and plasma nephrines in the evaluation of heat acclimatisation status

“…The autonomic nervous system (ANS) is central to cardiovascular regulation during and after exercise bouts (Iellamo 2001 ; Parekh and Lee 2005 ; Armstrong et al 2012 ). In animal models subject to chronic heat stress, ANS excitability measured ex vivo diminishes with the transition from STHA to LTHA (Horowitz and Meiri 1993 ; Horowitz 2014 , 2016 ).…”

Thermal dysregulation in patients with multiple sclerosis during SARS-CoV-2 infection. The potential therapeutic role of exercise

“…Autonomic processes such as skin vasodilation and sweat production are compensatory procedures to maintain body temperature at a normal level ( Kenny and McGinn, 2017 ; Nagashima et al, 2012 ). Exercise-induced hyperthermia impairs the function of ANS, which is measurable by heart rate variability and lasts > 80 min after the exercise session ( Armstrong et al, 2012 ). Thus, other factors can restore body heat balance.…”

Reliability of Biomarkers of Physiological Stress at Rest and Post-exertional Heat Stress

“…During heat stress the autonomic nervous system (ANS) buffers increased competition for blood flow between cutaneous circulation and skeletal muscle [8] and is central to cardiovascular regulation during and following a dynamic bout of exercise [9][10][11].…”

“…During heat stress the autonomic nervous system (ANS) buffers increased competition for blood flow between cutaneous circulation and skeletal muscle [8] and is central to cardiovascular regulation during and following a dynamic bout of exercise [9][10][11]. Observable measures of ANS disturbance and sympathetic activity include catecholamine's adrenaline and noradrenaline [4,12].…”