Trial of Testosterone Undecanoate for Optimizing Performance During Military Operations

Inclusion Criteria: * Men aged 18-35 years * Ability to understand verbal or written instructions/testing materials in English * Physically active (as determined by accelerometry and review of a physical activity log) * Not taking any prescription medications and/or willing to refrain from all medication use prior to and throughout the entire study period, unless provided/approved by the study physician * Willing to refrain from alcohol, smoking, e-cigarettes or use of any nicotine product, caffeine, and dietary supplement use throughout the entire study period * Willing to live on the Pennington Biomedical Research Center inpatient unit for 20 consecutive days * Meets age-specific US Army body composition standards according to Army Regulation 600-9, which includes estimates of percent body fat based on height, weight, and circumference measures (neck and waist) * Total testosterone concentration is within the normal physiological range (300-1,000 ng/dL) Exclusion Criteria: * Musculoskeletal injuries that compromise exercise capability * Diagnosed cardiometabolic disorders (i.e., hypertension, hyperlipidemia, kidney disease, diabetes, etc.) * Allergies or intolerance to foods, vegetarian practices, or history of complications with lidocaine * Anabolic steroid, human growth hormone, or nutritional testosterone precursor-like supplement use within the past 6 months * Will not refrain from smoking (any nicotine product), alcohol, caffeine, or any other dietary supplement during the study * Adults unable to consent * Women * Prisoners * Sedentary or engages in insufficient quantities of physical activity per week (aerobic and/or resistance training as determined by accelerometry and review of a physical activity log) * Exceeds age-specific US Army body composition standards according to Army Regulation 600-9 * Previous history of kidney stones unless otherwise approved by the medical investigator * Systolic blood pressure \> 150 or diastolic blood pressure \> 95 mmHg * Previous history of breast or prostate cancer * Previous history of Chronic Obstructive Pulmonary Disease or Obstructive Sleep Apnea * Prostate-Specific Antigen (PSA) \> 3ng/ml, Hematocrit \> 50%, or positive urine drug screening * Based on the investigative team's clinical judgment, a subject may not be appropriate for participation in the study