The Effects of Repeated Operational Stress and Limited Recovery on Resilience Capacity

This longitudinal study will examine the effects of repeated bouts of operational stress and limited recovery on integrated MPS, whole-body protein balance, iron absorption, and aerobic performance. Following baseline characterization measures, active adults (n=24) representative of normal weight phenotype (NW; n=12) and overweight phenotype (OW; n=12) will complete a 48h balance phase preceding two rounds of repeated 72h energy deficit exposure each immediately followed by a 48h recovery phase. NW cutoff will be defined ≤ 22% body fat for males and ≤ 32% body fat for females. OW cutoff will be defined as \>22% body fat for males and \>32% body fat for females. These body composition cutoffs are informed by the maximum allowable percent body fat standards outlined in current Army Regulation 600-9. Additional details for determining % body fat are outlined in the experimental procedures section of the protocol.

Inclusion Criteria: * Men and women aged 18 - 39 years (17 - 39 years if military personnel) * Weight stable in the past 2 months (± approximately 5 kg) * Healthy without evidence of chronic illness or musculoskeletal injury as determined by the USARIEM Office of Medical Support and Oversight (OMSO) or home duty station medical support (HMS) * Functional exercise (i.e., step ups, box jumps, body mass movements) and/or aerobic exercise trained defined by self-report as performing ≥ 2 sessions/wk for previous 6 months * Willing to refrain from alcohol, smoking any nicotine product (includes e-cigarettes); vaping, chewing tobacco, caffeine not provided in the study, and dietary supplement use throughout the dietary interventions * Biological females must be on sustained (i.e., approximately \>3 months) oral/hormonal contraceptive use which acts to maintain continuous hormonal levels (i.e., contains low-dose estrogen/progesterone with no oral placebos, hormonal IUD) * Supervisor approval for federal civilian employees and non-HRV active duty military personnel) Exclusion Criteria: * Musculoskeletal injuries that compromise exercise capability as determined by OMSO or HMS * Metabolic or cardiovascular abnormalities, sleep disorders (i.e., sleep apnea) gastrointestinal disorders (e.g., kidney disease, diabetes, cardiovascular disease, etc.) as determined by OMSO or HMS * Abnormal or problems with blood clotting as determined by OMSO or HMS * History of complications with lidocaine or similar local anesthetic analogue * Present condition of alcoholism, anabolic steroids, or other substance abuse issues * Blood donation within 8-wk of beginning or completing study blood draws * Current diagnosis of Anemia (hemoglobin \< 13 g/dL for males, hemoglobin \< 12 g/dL for females) and Sickle Cell Anemia/Trait as determined by OMSO or HMS * Pregnant, trying to become pregnant, and/or breastfeeding (results of urine pregnancy test or self-report for breastfeeding will be obtained before body composition testing) * Claustrophobia or discomfort related to having enclosed equipment around the head * Unwillingness or inability to consume study diets or foods provided due to personal preference or food allergies/sensitivities * Unwillingness or inability to adhere to study exercise restrictions and prescriptions