The Effect of Hydration Status on Substrate Oxidation at Rest and During Light and Moderate Exercise
Metabolic flexibility is the ability to properly switch between fat and carbohydrate stores to use for energy under different conditions (rest, feeding, exercise). Impairments in metabolic flexibility, also known as metabolic inflexibility, have been suggested to be an underlying cause of metabolic disease, like type 2 diabetes. Long-term low fluid intake may increase the risk of type 2 diabetes due to insulin resistance, a form of metabolic inflexibility. Further, low fluid intake has been shown to impair the ability to switch fuel preference during exercise. While there is some evidence that low fluid intake may lead to impaired metabolic flexibility, more information is needed. Therefore, the purpose of this study is to evaluate the impact of hydration status on substrate preference at rest and during exercise at varying intensities (light and moderate). Further, we will examine whether biological sex and menstrual cycle phase impact hydration and metabolism under these same conditions.
• Subject is male or female
• If female, subject is not pregnant (based on self-report)
• If female, subject has stopped taking birth control medication or removed long-acting reversible contraceptive \>6 months at start of the study
• If female, subject has normal menstrual cycle (21-35 days)
• If female, subject is willing to track their menstrual cycle
• If female, subject has a smartphone compatible for application to track menstrual cycle (female only) and/or wearable data (females and males)
• Subject is 18-35 years of age, inclusive
• Subject body mass index (BMI) is between 18.5-25 kg/m2
• Subject is at least recreationally active (engaged in moderate-intensity, intermittent, or steady-state exercise at least 3 days per week for at least 60 min at a time)
• Subject is accustomed to cycling for at least 60 min
• Subject does not smoke (or has quit for at least 6 months)
• Subject is not taking medication that may interfere with the study (e.g., diuretics, laxatives, or weight loss drugs)
• Subject has no health conditions that would interfere with the study as indicated on the general health questionnaire (GHQ) e.g. cardiovascular, renal, or metabolic diseases
• Subject is not actively involved in weight loss intervention (dieting and/or anti-obesity medications)
• Subject is not allergic to adhesives (e.g., medical tape)
• Subject is willing to avoid alcohol consumption 24 hours prior to visit(s)
• Subject is willing to fast overnight (\
⁃ 8-12 hours)
• Subject is willing to refrain from vigorous exercise for 24 hours (light physical activity only)
• Subject is willing to be shaved at patch or electrode site, if necessary
• Subject is willing to eat the exact same food the day prior to each visit to the laboratory
• Able to speak, write, and read English
• Provision of written consent to participate