Neurovascular coupling during dynamic upper body resistance exercise in healthy individuals

During unilateral static and rhythmic handgrip exercise, middle cerebral artery blood velocity (MCAv) increases in the contralateral side to the exercising limb. However, whether this neurovascular coupling-mediated increase in contralateral MCAv is apparent against a background of fluctuating perfusion pressure produced by dynamic resistance exercise (RE) is unclear. We examined the cerebral haemodynamic response to unilateral dynamic RE in 30 healthy individuals (female = 16, mean ± SD: age, 26 ± 6 years; height, 175 ± 10 cm; weight, 74 ± 15 kg; body mass index, 24 ± 5 kg m^-2). Participants completed four sets of 10 paced repetitions (15 repetitions min^-1) of unilateral bicep curl exercise at 60% of the predicted one-repetition maximum (7 ± 3 kg). Beat-to-beat blood pressure, bilateral MCAv and end-tidal carbon dioxide were measured throughout. One-way ANOVA was used to analyse cardiovascular variables and two-way ANOVA to analyse dependent cerebrovascular variables (side × sets, 2 × 5). A linear mixed model analysis was also performed to investigate the effects of end-tidal carbon dioxide and mean arterial blood pressure on MCAv. In comparison to baseline, within-exercise mean arterial blood pressure increased (P < 0.001) across the sets, whereas bilateral MCAv decreased (P < 0.001). However, no significant interaction effect was observed for any dependent variables (all P > 0.787). The linear mixed model revealed that end-tidal carbon dioxide had the greatest effect on MCAv (estimate = 1.019, t = 8.490, P < 0.001). No differences were seen in contralateral and ipsilateral MCAv during dynamic RE, suggesting that neurovascular coupling contributions during dynamic RE might be masked by other regulators, such as blood pressure.