Does habitual endurance exercise protect endothelial function against acute exposure to oscillatory shear stress?

Abstract

Introduction: Acute exposure to increases in oscillatory shear stress (increased retrograde shear stress and decreased mean shear stress) reduces flow-mediated dilation (FMD). This impairment may be mediated via increased oxidative stress. Habitual endurance exercise training results in increased antioxidant protection. However, it is currently unknown whether these adaptations protect against oscillatory shear stress-induced impairments in FMD.
 Purpose and Hypothesis: The purpose of this study is to determine whether lower limb endurance-trained athletes have protection against oscillatory shear stress-induced impairments in FMD compared to sedentary individuals. It is hypothesized that athletes will have a preserved FMD after an acute oscillatory shear stress intervention, compared to their sedentary counterparts.
 Methods: Healthy, young adult volunteers (18-29 years old) will be screened for physical activity (PA) through a physical activity recall questionnaire. 12 sedentary individuals (<3h of structured PA/week) and 12 lower limb endurance athletes will be recruited to participate. All participants will complete a VO2 peak test to objectively measure cardiorespiratory fitness. Participants will visit the laboratory twice in the same week for vascular testing. Both 90-minute visits will begin with 45 minutes of supine rest, followed by a brachial artery FMD test before and after 30 minutes of either imposed oscillatory shear stress (forearm cuff inflated to 70 mmHg) or a 30 min rest period (control). 
 Significance: This will be the first study to investigate whether endurance-trained athletes are resistant to oscillatory shear-stress induced impairments in endothelial function. This will provide insight into mechanism contributing to the vasoprotective effects of habitual endurance exercise.