Neurovascular Coupling is Unchanged during Sitting, Standing or Walking: Implications for Active Work Stations

Abstract

Neurovascular coupling (NVC) is a phenomenon that matches regional cerebral blood flow to local neuronal metabolic activity. Improvements in NVC may underlie the qualitative reports of improved cognitive performance using standing and active workstations. However, little has been investigated pertaining to body position and the potential effects of sitting, standing or walking on NVC. We hypothesized that sitting, standing and low intensity treadmill walking (2 mph) would increase NVC magnitude in a dose-dependent fashion. We recruited 20 young, healthy participants (n=20, 11 females), and instrumented them with an electrocardiogram (beat-by-beat heart rate; HR; bpm), finger photoplethysmography (mean arterial pressure; MAP; mmHg) and transcranial Doppler ultrasound to quantify posterior cerebral artery velocity (PCAv; cm/s) during sitting, standing and walking trials. Each position included a protocol consisting of a 3-min baseline (BL) and three x 30-sec standardized visual stimulus (VS) periods using a 6 Hz strobe light held 15cm away from the eyes. Responses were quantified through (a) visually identified peak(s) PCAv during VS, (b) time to peak peak(s) and (c) mean PCAv response(s) during VS, with all three measures averaged for a representative response for each individual. NVC magnitude was then quantified as a change (delta) in peak and mean responses from BL. At baseline, HR was incrementally higher in sitting, standing and walking (P<0.001), but MAP was unchanged between positions (P=0.12). There were significant increases in the peak and mean responses from BL in all positions during VS (P<0.001), confirming an NVC response. However, there were no differences in delta peak (P=0.47), time-to-peak (P=0.29) nor delta mean (P=0.76) NVC responses during VS across all positions. These results suggest that NVC magnitude is unaffected by body position or low intensity physical activity. We conclude that reports of increased cognitive performance while using standing or active work stations in the workplace are not related to NVC, and are likely related to nervous system activation and/or changes in systemic metabolic rate.