Impact of Acute Uninterrupted Sitting on Cerebrovascular Hemodynamics

Reductions in brain blood flow are associated with reduced cognitive function and cerebrovascular disease. Acute periods of uninterrupted sitting can lead to endothelial dysfunction, namely due to a reduction in shear stress and subsequent reduction in nitric oxide bioavailability. Little is known of the impact of sitting on brain health. The purpose was to determine the total brain blood flow response following a 60-minute bout of uninterrupted sitting. Using a parallel design, this study evaluated the impact of 60-minutes of sitting on total brain blood flow. Fifteen participants (n=15; age=24 ± 1yr; BMI=25 ± 1 kg/m²) sat, uninterrupted, for 60-minutes during the SIT protocol. To ascertain the contribution of blood pooling effects on total brain blood flow, ten participants (n=10; age=23±2yr; BMI=27±4 kg/m²) sat in a modified sitting (MOD) for 60-minutes. Finally, thirteen participants (n=13; age=23±3yr; BMI=26±4 kg/m²) remained supine for the duration of the 60-minutes as a time-control (TC). Brain blood flow was quantified through Doppler-ultrasound measurements of blood flow through the internal carotid (ICA) and vertebral (VA) arteries: (ICA blood flow + VA blood flow) × 2. Following the 60-minutes of sitting (SIT), there was a significant reduction in brain blood flow with time (p=0.001, η =0.05). Total brain blood flow did not significantly change in MOD (p=0.69, η =0.05) or TC (p=0.06, η =0.58) conditions. These findings indicate 60-minutes of sitting may alter cerebrovascular hemodynamics characterized by a reduction in total brain blood flow.