Date of Award

Fall 12-1-2020

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

School

Kinesiology and Nutrition

Committee Chair

Dr. Scott G. Piland

Committee Chair School

Kinesiology and Nutrition

Committee Member 2

Dr. Stephanie M. McCoy

Committee Member 2 School

Kinesiology and Nutrition

Committee Member 3

Dr. Jennifer L. Lemacks

Committee Member 3 School

Kinesiology and Nutrition

Committee Member 4

Dr. Daniel P. Credeur

Abstract

Emerging evidence suggests that uninterrupted sitting has a deleterious impact on hemodynamics, namely a reduction in blood-flow induced shear stress in peripheral vessels, which leads to vascular dysfunction and increased arterial stiffness. Few studies have examined the cerebrovascular response, and no studies have discerned potential racial differences on the hemodynamic response to uninterrupted sitting. Purpose: To examine racial differences in the hemodynamic response during an acute period (1-hour) of uninterrupted sitting between Black/African American and White males. Methods: Twenty-four adult males (50% Black/African American) between the ages of 18 and 35 years and relatively healthy (i.e., free of overt disease) were recruited. Measurements were taken at four time-points—baseline, during 1-h of sitting, and post 1-hour of uninterrupted sitting. Cerebrovascular hemodynamics, measured using duplex Doppler-ultrasonography, were measured at all time-points. Arterial stiffness, using carotid-femoral pulse wave velocity (cfPWV) was measured at baseline and post 1-hour of uninterrupted sitting. Results: Blood flow through the internal carotid artery (ICA) was, on average, lower in Black/African American males at all time points, except post-sitting measurement, compared with White males, though nonsignificant (p=0.27). Blood flow through the vertebral artery (VA) did not differ by race, however there was a significant effect for time suggesting a reduction in blood flow during the sitting period (p=0.009). Estimated total brain blood flow did not differ by race (p=0.63), however blood flow was significantly higher at baseline than following the hour of uninterrupted sitting (p=0.04). Arterial stiffness did not differ by race, though Black/African American males had higher cfPWV at both measured time-points. From baseline to post-sitting, there was a significant increase in cfPWV (p=0.01). Changes in cfPWV were not associated with changes in total brain blood flow at baseline or following the uninterrupted sitting period in Black/African American or White males (p>0.05). Conclusions: An acute 1-hour period of uninterrupted sitting negatively impacts hemodynamics, an effect that appears to be similar between Black/African American and White men. Future research should examine the time course of change, repeated exposures to acute periods of sitting, interrupting sitting time, and observing relationships with arterial stiffness in other racial/ethnic population.

ORCID ID

orcid.org/0000-0001-9241-2309

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