THE EFFECTS OF A PRIOR EXERCISE BOUT ON THE ENERGETIC AND CARDIOMETABOLIC RESPONSES TO ACUTE MENTAL STRESS

Background: Mental stress is associated with cardiovascular disease (CVD) risk, but the arterial stiffness and energy expenditure (EE) responses to acute mental stress, and whether prior exercise impacts post-stress cardiometabolic reactivity are not known. The objectives of this dissertation were to assess arterial stiffness and EE responses to acute mental stress and to determine the impact of a prior exercise bout on these responses. Methods: In addition to a meta-analysis on the effects of acute mental stress on arterial stiffness, this dissertation entailed two randomized cross-over studies. Forty recreationally active young adults (18-30 y) were recruited. For Cross-over 1, 20 participants attended two laboratory visits: i) Trier Social Stress Test (arithmetic + speech), and ii) Control. For Cross-over 2, 20 different participants attended two laboratory visits: i) Exercise + Trier Social Stress Test (psychosocial task), and ii) Exercise + Control. Exercise consisted of 25 minutes of moderate-intensity elliptical. Arterial stiffness and EE were measured by pulse-wave velocity (PWV) and indirect calorimetry, respectively. Measurements took place pre, during (EE only), and post condition. Mixed model linear regression assessed condition x time interactions. Results: Meta-analysis: Across 17 trials from 9 studies, exposure to acute mental stress caused arterial stiffness to increase (Standardized Mean Difference: 0.45; p<0.05). Cross-over 1: There was a small interaction (B=0.68 m/s, 95%CI: 0.39, 0.97) for PWV [Stress: 0.81 m/s, Control: 0.15 m/s]. There was also a small interaction (B=0.0010 kcal/kg/min, 95%CI: 0.0004, 0.0015) for EE (Stress: 0.0016 kcal/kg/min, Control:0.0005 kcal/kg/min). Cross-over 2: There was a small interaction (B=0.47 m/s, 95%CI: 0.21, 0.72) for PWV (Stress: 0.43 m/s, Control: -0.05 m/s). For EE, there were small main effects of condition (B=0.0005 kcal/kg/min), 95%CI: 0.0003, 0.0008) and time (B=0.0011 kcal/kg/min, 95%CI: 0.0006, 0.0016). Compared to Cross-over 1, the prior exercise introduced in Cross-over 2 dampened the arterial stiffness and EE responses. Conclusions: Arterial stiffness and EE may be key players in the relationship between acute mental stress and CVD risk, and exercise may beneficially moderate this relationship. Future research examining the stress-CVD paradigm, including potential protective effects of exercise, will be necessary to inform stress-related CVD prevention and treatment efforts.Doctor of Philosoph