Six weeks of high-intensity interval training to exhaustion attenuates dynamic cerebral autoregulation without influencing resting cerebral blood velocity in young fit men.

Audrey Drapeau,Olivier Le Blanc,Simon Malenfant,Patrice Brassard,Lawrence Labrecque,Myriam Paquette,Sarah Imhoff

doi:10.14814/phy2.14185

Abstract

Elevated cardiorespiratory fitness (CRF) is associated with reduced dynamic cerebral autoregulation (dCA), but the impact of exercise training per se on dCA remains equivocal. In addition, resting cerebral blood flow (CBF) and dCA after high‐intensity interval training (HIIT) in individuals with already high CRF remains unknown. We examined to what extent 6 weeks of HIIT affect resting CBF and dCA in cardiorespiratory fit men and explored if potential changes are intensity‐dependent. Endurance‐trained men were assigned to group HIIT85 (85% of maximal aerobic power, 1–7 min effort bouts, n = 8) and HIIT115 (115% of maximal aerobic power, 30 sec to 1 min effort bouts, n = 9). Training sessions were completed until exhaustion 3 times/week over 6 weeks. Mean arterial pressure (MAP) and middle cerebral artery mean blood velocity (MCAvmean) were measured continuously at rest and during repeated squat‐stands (0.05 and 0.10 Hz). Transfer function analysis (TFA) was used to characterize dCA on driven blood pressure oscillations during repeated squat‐stands. Neither training nor intensity had an effect on resting MAP and MCAvmean (both P > 0.05). TFA phase during 0.10 Hz squat‐stands decreased after HIIT irrespective of intensity (HIIT85: 0.77 ± 0.22 vs. 0.67 ± 0.18 radians; HIIT115: pre: 0.62 ± 0.19 vs. post: 0.59 ± 0.13 radians, time effect P = 0.048). These results suggest that HIIT over 6 weeks have no apparent benefits on resting CBF, but a subtle attenuation in dCA is seen posttraining irrespective of intensity training in endurance‐trained men.

Highlights

Established evidence show that cardiorespiratory fitness (CRF) is more cardioprotective when compared to overall physical activity levels [19]
Excessive noise/artifact in the recordings of two participants (HIIT85, n = 1; HIIT115, n = 1), did not allow for Transfer function analysis (TFA) measurements, a total of 15 participants were included in the dynamic cerebral autoregulation (dCA) analysis
Effect of high-intensity interval training (HIIT) on dynamic cerebral autoregulation We have previously demonstrated cross-sectionally that dCA is impaired in endurancetrained men with elevated CRF [17]

Summary

Introduction

Established evidence show that cardiorespiratory fitness (CRF) is more cardioprotective when compared to overall physical activity levels [19]. Evidence show that lifelong aerobic training individuals with elevated CRF have higher resting intracranial blood velocity in the anterior circulation, (as indexed by transcranial Doppler sonography of mean blood velocity in middle cerebral artery (MCAvmean) [3, 7], and in the posterior circulation (as indexed by arterial spin labelling in posterior cingular cortex/precuneus) [37] and higher extracranial blood flow (as indexed by carotid Doppler) [9] than their sedentary counterparts. Short-term aerobic training (12 weeks) longitudinally elevates CRF and cerebrovascular reactivity to carbon dioxide, whereas it induces equivocal MCAvmean responses at rest [26]. Whether exercise training can elevate resting CBF in individuals with high CRF remains to be determined

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