Abstract

The effect that cardiorespiratory fitness has on the dynamic cerebral autoregulatory capacity during changes in mean arterial pressure (MAP) remains equivocal. Using a multiple‐metrics approach, challenging MAP across the spectrum of physiological extremes (i.e., spontaneous through forced MAP oscillations), we characterized dynamic cerebral autoregulatory capacity in 19 male endurance athletes and eight controls via three methods: (1) onset of regulation (i.e., time delay before an increase in middle cerebral artery (MCA) conductance [MCA blood velocity (MCAv)/MAP] and rate of regulation, after transient hypotension induced by sit‐to‐stand, and transfer function analysis (TFA) of MAP and MCAv responses during (2) spontaneous and (3) forced oscillations (5‐min of squat‐stand maneuvers performed at 0.05 and 0.10 Hz). Reductions in MAP and mean MCAv (MCAV mean) during initial orthostatic stress (0‐30 sec after sit‐to‐stand) and the prevalence of orthostatic hypotension were also determined. Onset of regulation was delayed after sit‐to‐stand in athletes (3.1 ± 1.7 vs. 1.5 ± 1.0 sec; P = 0.03), but rate of regulation was not different between groups (0.24 ± 0.05 vs. 0.21 ± 0.09 sec−1; P = 0.82). While both groups had comparable TFA metrics during spontaneous oscillations, athletes had higher TFA gain during 0.10 Hz squat‐stand versus recreational controls (P = 0.01). Reductions in MAP (P = 0.15) and MCAV mean (P = 0.11) during orthostatic stress and the prevalence of initial orthostatic hypotension (P = 0.65) were comparable between groups. These results indicate an intact ability of the cerebral vasculature to react to spontaneous oscillations but an attenuated capability to counter rapid and large changes in MAP in individuals with elevated cardiorespiratory fitness.

Highlights

  • Regular aerobic endurance exercise has been associated with higher resting cerebral blood velocity in men (Ainslie et al 2008), while higher cardiorespiratory fitness (CRF) has been shown to improve cerebral blood velocity during exercise (Brugniaux et al 2014), as well as cerebrovascular reactivity to carbon dioxide

  • Reductions in mean arterial pressure (MAP) (P = 0.15) and MCAVmean (P = 0.11) during orthostatic stress and the prevalence of initial orthostatic hypotension (P = 0.65) were comparable between groups. These results indicate an intact ability of the cerebral vasculature to react to spontaneous oscillations but an attenuated capability to counter rapid and large changes in MAP in individuals with elevated cardiorespiratory fitness

  • Comparable dynamic cerebral autoregulatory capacity between endurance athletes and sedentary controls has been reported following thigh-cuff deflation (RoR, rate of regulation) and via transfer function analysis (TFA; coherence – fraction of the MAP which is linearly related to MCAv, gain – amplitude of MCAv change for a given oscillation in MAP, and phase – difference in the timing of the MAP and MCAv waveforms) of spontaneous or forced oscillations in MAP and MCAv in young and elderly athletes (Aengevaeren et al 2013; Ichikawa et al 2013)

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Summary

Introduction

Regular aerobic endurance exercise has been associated with higher resting cerebral blood velocity in men (Ainslie et al 2008), while higher cardiorespiratory fitness (CRF) has been shown to improve cerebral blood velocity during exercise (Brugniaux et al 2014), as well as cerebrovascular reactivity to carbon dioxide A weakened dynamic cerebral autoregulatory capacity, characterized by a delayed onset of regulation following transient hypotension induced by thigh-cuff deflation and larger normalized transfer function gain of spontaneous oscillations in MAP and blood velocity in the middle cerebral artery (MCAv), has been reported in endurance athletes compared to sedentary controls (Lind-Holst et al 2011). Taking into consideration the notion that most metrics are unrelated to each other (Tzeng et al 2012), direct comparison between studies using different analysis techniques may lead to inconsistent physiological information (Tzeng et al 2012; Tzeng and Ainslie 2014) Maneuvers such as the sit-to-stand may provide more realistic data closer to daily life in comparison with data gathered with the thigh-cuff deflation technique. To the best of our knowledge, there is no published report, which examined the dynamic cerebral autoregulatory capacity in endurance athletes using the sit-to-stand maneuver

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