High Altitude and Exogenous Carbohydrate Oxidation

Inclusion Criteria: * Men aged 18 - 39 years * Born at altitudes less than 2,100 m (\~7,000 feet; Examples include Santa Fe, New Mexico; Laramie, Wyoming; Etc.) * Physically active based on assessment of physical activity history (2-4 days per week aerobic and/or resistance exercise) * Have supervisor approval (permanent party military and civilians) * Willing to refrain from alcohol, smokeless nicotine products and dietary supplement use during study periods * Refrain from taking any nonsteroidal anti-inflammatory drugs (NSAIDs; e.g. aspirin, Advil®, Aleve®, Naprosyn®, or any aspirin-containing product) for 10 days before and at least 5 days AFTER each muscle biopsy. (\*Tylenol® or acetaminophen is ok to use if needed for discomfort) Exclusion Criteria: * Born at altitudes greater than 2,100 m (\~7,000 feet; Examples include Santa Fe, New Mexico; Laramie, Wyoming; Etc.) * Living in areas that are more than 1,200 m (\~4,000 feet), or have traveled to areas that are more than 1,200 m for five days or more within the last 2 months (Examples include Ft. Huachuca, Arizona; Lima, Peru; Feldberg, Germany, Etc.) * Musculoskeletal injuries that compromise exercise capability * Metabolic or cardiovascular abnormalities (determined by resting ECG), gastrointestinal disorders (e.g., kidney disease, diabetes, cardiovascular disease, etc.) * Medication that affects macronutrient metabolism (i.e., diabetes medications, statins, corticosteroids, etc) and/or the ability to participate in strenuous exercise * Evidence of apnea or other sleeping disorders * Prior diagnosis of high altitude pulmonary edema (HAPE) or high altitude cerebral edema (HACE) * Presence of asthma or respiratory tract infections (\< 1 month prior) * Allergies or intolerance to foods (including but not limited to lactose intolerance/milk allergy), vegetarian practices, or medications (including, but not limited to, lidocaine ) to be utilized in the study * Smoking or vaping * History of complications with lidocaine * Taking medications that interfere with oxygen delivery and transport (Includes sedatives, sleeping aids, tranquilizers and/or any medication that depresses ventilation, diuretics, alpha and beta blockers) * Evidence of any physical, mental, and/or medical conditions that would make the proposed studies relatively more hazardous as determined by the Office of Medical Support and Oversight * Present condition of alcoholism, anabolic steroids, or other substance abuse issues * Anemia (hematocrit \<38% and hemoglobin \<12.5 g/dL) and Sickle Cell Anemia/Trait * Abnormal prothrombin time (PT)/ partial thromboplastin time (PTT) test or problems with blood clotting * Blood donation within 8 weeks of beginning the study