Abstract
This study examined acute cerebral hemodynamic and circulating neurotrophic factor responses to moderate intensity continuous exercise (MICT), guideline-based high intensity interval exercise (HIIT), and sprint interval exercise (SIT). We hypothesized that the pattern of middle cerebral artery velocity (MCAv) response would differ between interval and continuous exercise, with SIT inducing the smallest increase from rest, while increases in neurotrophic factors would be intensity-dependent. In a randomized crossover design, 24 healthy adults (nine females) performed three exercise protocols: (i) MICT (30 min), (ii) HIIT (4 × 4 min at 85% HRmax), and (iii) SIT (4 × 30 s supramaximal). MCAv significantly increased from rest across MICT (Δ13.1 ± 8.5 cm⋅s–1, p < 0.001) and all bouts of HIIT (Δ15.2 ± 9.8 cm⋅s–1, p < 0.001), but only for the initial bout of SIT (Δ17.3 ± 11.6 cm⋅s–1, p < 0.001). Immediately following each interval bout, MCAv increased (i.e., rebounded) for the SIT (9–14% above rest, p ≤ 0.04), but not HIIT protocol. SIT alone induced significant elevations from rest to end-exercise in vascular endothelial growth factor (VEGF; Δ28 ± 36%, p = 0.017) and brain-derived neurotrophic factor (BDNF, Δ149% ± 162%, p < 0.001) and there were greater increases in lactate than in either other protocol (>5-fold greater in SIT, p < 0.001), alongside a small significant reduction at the end of active recovery in insulin-like growth factor 1 (IGF-1, Δ22 ± 21%, p = 0.002). In conclusion, while the nature of the response may differ, both guideline-based and sprint-based interval exercise have the potential to induce significant changes in factors linked to improved cerebrovascular and brain health.
Highlights
Physical activity is unique in its ability to positively impact human health and promote wellbeing across a lifespan (Pedersen and Saltin, 2015; O’Donovan et al, 2017; Kraus et al, 2019)
Given the potential impact of exercise intensity and protocol on cerebrovascular function, this study aimed to examine the middle cerebral artery velocity (MCAv) response to moderate intensity continuous exercise (MICT), guideline-based high intensity interval exercise (HIIT), and sprint interval exercise (SIT)
It was hypothesized that the pattern of middle cerebral artery velocity (MCAv) response would differ between interval and continuous exercise, with SIT inducing the smallest increase from rest
Summary
Physical activity is unique in its ability to positively impact human health and promote wellbeing across a lifespan (Pedersen and Saltin, 2015; O’Donovan et al, 2017; Kraus et al, 2019). While current evidence indicates comparable middle cerebral artery velocity (MCAv) responses between continuous and interval-based moderate intensity exercise (Klein et al, 2019), MCAv has been shown to be suppressed over the course of a single 30 s all-out sprint bout, followed by a marked elevation in MCAv during recovery (Curtelin et al, 2018; Labrecque et al, 2020) This reduction in response to high intensity interval-based strategies is in contrast to responses within the peripheral vasculature (Ramos et al, 2015), likely driven by the unique response of the cerebrovasculature to exercise-induced hyperventilatory hypocapnia (Ogoh and Ainslie, 2010), as well as differences in the regulatory responses to elevated systemic flow and blood pressure (Brassard et al, 2017; Ogoh et al, 2018; Calverley et al, 2020). While the current literature demonstrates the complex relationship between SIT and measures of cerebral hemodynamics (Curtelin et al, 2018; Labrecque et al, 2020), it is not clear whether these responses change over multiple bouts as is typical in training interventions, nor how SIT- and HIIT-based strategies may differ in their response
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