Cerebral blood flow, frontal lobe oxygenation and intra-arterial blood pressure during sprint exercise in normoxia and severe acute hypoxia in humans

Abstract

Cerebral blood flow (CBF) is regulated to secure brain O delivery while simultaneously avoiding hyperperfusion; however, both requisites may conflict during sprint exercise. To determine whether brain O delivery or CBF is prioritized, young men performed sprint exercise in normoxia and hypoxia (PO = 73 mmHg). During the sprints, cardiac output increased to ∼22 L min, mean arterial pressure to ∼131 mmHg and peak systolic blood pressure ranged between 200 and 304 mmHg. Middle-cerebral artery velocity (MCAv) increased to peak values (∼16%) after 7.5 s and decreased to pre-exercise values towards the end of the sprint. When the sprints in normoxia were preceded by a reduced PCO, CBF and frontal lobe oxygenation decreased in parallel ( r = 0.93, P < 0.01). In hypoxia, MCAv was increased by 25%, due to a 26% greater vascular conductance, despite 4-6 mmHg lower PaCO in hypoxia than normoxia. This vasodilation fully accounted for the 22 % lower CaO in hypoxia, leading to a similar brain O delivery during the sprints regardless of PO. In conclusion, when a conflict exists between preserving brain O delivery or restraining CBF to avoid potential damage by an elevated perfusion pressure, the priority is given to brain O delivery.

Regulation of cerebral blood flow and metabolism during exercise

“…Nevertheless, it should be noted that blood pressure may have an influence on the CBF response during rapid surges in blood pressure induced by resistance exercise (Edwards et al 2002), certain modes of exercise, such as rowing (Pott et al 1997), or high-intensity interval exercise (reviewed by Lucas et al 2015). With regard to high-intensity interval exercise, this could become problematical for the brain only when neuroprotective mechanisms (dynamic cerebral autoregulation, cerebral sympathetic nervous activity and cerebrovascular reactivity to CO 2 ) are altered, because recent work suggests that the human brain seems to restrain CBF to avoid potential damage by an increase in blood pressure during sprint exercise (Curtelin et al 2017). Broadly consistent with this finding is the evidence that the brain is better at buffering transient hypertension Brassard et al 2017) than hypotension.…”

“…With regard to high‐intensity interval exercise, this could become problematical for the brain only when neuroprotective mechanisms (dynamic cerebral autoregulation, cerebral sympathetic nervous activity and cerebrovascular reactivity to CO 2 ) are altered, because recent work suggests that the human brain seems to restrain CBF to avoid potential damage by an increase in blood pressure during sprint exercise (Curtelin et al . ). Broadly consistent with this finding is the evidence that the brain is better at buffering transient hypertension (Tzeng et al .…”

Comparable blood velocity changes in middle and posterior cerebral arteries during and following acute high‐intensity exercise in young fit women

“…HIIT is distinctive from progressive aerobic exercise to exhaustion, as it includes short exercise bouts of near‐ to supra‐maximal intensity, associated with marked rapid increases in BP. Therefore, maximal BP values are reached sooner, and in a much more sudden manner during HIIT than progressive aerobic exercise to exhaustion (e.g., during a O 2 max protocol) (Calbet et al., 2015; Curtelin et al., 2018; Tsukamoto et al., 2018). Repetitive sudden elevations in MAP induced by acute high‐intensity exercise could be transmitted to the brain and could cause damage if not adequately buffered by neuroprotective mechanisms [reviewed in (Lucas et al.…”

“…The temporal response of cerebral blood flow to a rapid surge in blood pressure (BP) induced by either one high‐intensity exercise bout or a succession of high‐intensity exercise intervals is not well described. To the best of the authors’ knowledge and among all studies interested in the regulation of cerebral blood flow during HIIT, only one study examined cerebral blood velocity (CBV) changes during a single high‐intensity exercise bout (Curtelin et al., 2018). Specifically, during a 30‐s all‐out sprint exercise performed by young healthy participants, Curtelin et al.…”

“…Of note, only young healthy men were examined by Curtelin et al. (2018). Considering the impact of sex on various cerebral blood flow determinants (Favre & Serrador, 2019; Gur et al., 1982; Kastrup, Thomas, Hartmann, & Schabet, 1997; Labrecque et al., 2019), these findings cannot be directly translated to young healthy women.…”