Insufficient sleep is associated with an increased risk for cardiovascular disease. The causal mechanisms are currently unknown, but may include endothelial dysfunction. The purpose of this study is to examine the influence of sex and aging on the effects of total sleep deprivation on vascular function and whether exercise training attenuates these effects.

Inclusion criteria:

• Males and females
• 20 to 30 and 50 to 60 years of age
• Females will be eumenorrheic at enrollment or postmenopausal for at least 1 year
• No major clinical disease (e.g., diabetes, cardiovascular, liver or chronic kidney disease) to minimize confounding of vascular measures
• Participants will be sedentary (≤3x per week of ≤30 minutes of aerobic exercise/session) or trained (≥5x per week of moderate/vigorous aerobic exercise training)

Exclusion criteria:

• Age <20 or 31 to 49 or >60 years
• Body mass index ≥30 kg/m^2 because obesity may affect vascular function
• Use of medication that may affect vascular measures
• Hormone replacement therapy or hormonal contraceptives within past year
• Use of tobacco products (chewing tobacco, traditional or e-cigarettes) because they may influence vascular function
• Being perimenopausal, pregnant or lactating because may influence vascular function
• Being a shift worker because habitual sleep deprivation and altered circadian rhythm may influence vascular function.
• Not having an "intermediate" chronotype based on the Morningness-Eveningness Questionnaire (MEQ; score <31 or >69) because this would influence the effect of overnight sleep deprivation on vascular function.
• Sleep complaints based on the Pittsburgh Sleep Quality Index (PSQI; score >5) because this would influence the effect of overnight sleep deprivation on vascular function.