Early-Morning and Late-Night Maximal Runs: Metabolic and Perceived Exertion Outcomes

People may exercise at the ends of their day to fit activity into their schedule; the purpose of this investigation was to determine if metabolic or perceived exertion outcomes differed between maximal runs early in the morning and late at night. After consuming a standardized, glucose drink, thirteen recreationally active individuals completed an early-morning and a late-night run on the treadmill while researchers measured metabolic (aerobic capacity and substrate usage) and perceived exertion outcomes. Point of application #1: Aerobic capacity (maximal consumption of oxygen) and the usage of fat as a fuel to support energy production during exercise were similar between runs. Point of application #2: Maximal perceived exertion (Borg’s 6-20) was similar during early-morning and late-night runs. Point of application #3: While research indicates that people may prefer activity in the morning or evening, and this might impact metabolic responses to the exercise bout, most of our participants (n=8) identified with no preference for exercising in the early-morning or late-night. Key Words: glucose; CHO shake; VO2max; fat oxidation; effor