Obesity is associated with a decrease in skeletal muscle insulin sensitivity. Aerobic exercise can increase insulin sensitivity in the few hours following exercise, however the cellular mechanisms are not completely understood. The current project is to investigate mechanisms of exercise improvements to skeletal muscle insulin sensitivity.

Study Overview: We are investigating the mechanisms by which exercise improves the response of skeletal muscle to insulin in lean and obese adults. Participants will complete 4 study visits consisting of: 1) screening visit, 2) maximal exercise test visit, and then a randomized order of 3) a resting metabolic study visit, and 4) an exercise metabolic study visit. Metabolic study visits for resting and exercise conditions will be identical, other than remaining sedentary or performing exercise. Skeletal muscle biopsy samples will be collected during resting, immediately post-exercise and during insulin stimulated conditions.

Inclusion Criteria:

• Males or Females
• Aged 18-45 years
• Normal weight (body mass index [BMI] 18-26 kg/m2) or obese (BMI 30-46 kg/m2)
• Sedentary (< 1 hour of planned physical activity per week for ≥ 6 months)
• Weight stable (< 2 kg change in body mass for ≥ 6 months)
• Non-smokers (no tobacco or nicotine use for ≥ 1 year)

Exclusion Criteria:

• Hypertension (systolic blood pressure >140 mmHg, diastolic blood pressure > 90mmHg)
• Chronic health condition including diabetes, cardiovascular disease, treated hypertension, cancer, anemia, uncontrolled hyper- or hypothyroidism.
• Pregnant, nursing, irregular menses or post-menopausal (if female)
• Hyperglycemia (fasting glucose >126 mg/dl)
• Hypercholesterolemia (fasting LDL>140mg/dl)
• Hemoglobin < 13.0 g/dl (males), < 11.5 g/dl (females)
• Compromised renal function (outside 135-145 mmol/L sodium, 3.5-5.1 mmol/L potassium)
• Lidocaine allergy
• Medications including β-blockers, angiotensin converting enzyme inhibitors, insulin, thiazolidinediones, metformin, sulfonylureas, chronic non-steroidal anti-inflammatory use, anti-coagulant (e.g. warfarin), current antibiotics, opiates, monoamine oxidase inhibitors, benzodiazepines, or others that may impact the study outcomes
• Any physical limitation that prevents a participant from safely completing the exercise test
• Due to the risks associated with the current protocol, individuals with a diminished capacity to consent will be excluded. Similarly, due to the need for constant, accurate participant monitoring during metabolic study activities, participants will need to clearly understand verbal and written English. Participants who cannot clearly understand verbal and written English will be excluded.