Association Between Allostatic Load Index And Physical Performance And Psychosocial Responses During Arduous Military Training

Military personnel may be required to deploy or report to a subsequent duty station shortly after military training to necessitate physical and psychosocial adaptation. However, such personnel display maladaptation from training thought attributed to allostatic load, defined as a model outlining a maladaptive biological process triggered by chronic stress that results in physiological dysregulation. Understanding the influence of allostatic load quantified by the Allostatic Load Index (ALI) - a cumulative score derived from dichotomized biomarkers across stress-related systems associated with stress pathophysiology - on robust measures of physical and psychosocial maladaptation may help clarify the biological processes underlying maladaptation and inform preventive means to enhance post-training performance. PURPOSE: To examine the relationship between change in ALI and physical performance and psychosocial responses in personnel undergoing a 10-wk Marine Corps Officer Candidates School (OCS). METHODS: Thirty-one participants (14 women) provided biochemical, questionnaire (perceived stress appraisal (PSS), sleep difficulty (SD), resilience (CD-RISC-25), and OCS Physical Fitness Test (PFT; three-mile run [3MR], pullups, Run-Row PFT score, Push-Pull PFT score, Crunches-Plank PFT score, and total PFT score)) data before and after OCS. ALI (0-8) was calculated from eight biomarker components of neuroendocrine (cortisol, DHEA, cortisol:DHEA), autonomic (α-amylase), and immune (IL6, IL10, CRP, TNFα) systems. Simple linear regression analysis assessed the association between change (Δ) in ALI and responses (α = 0.05). RESULTS: In men, ΔALI was associated with Δpullups (β = -0.88, p = 0.015, R2 = 0.60), ΔPush-Pull PFT score (β = -2.87, p = 0.013, R2 = 0.60), Δtotal PFT score (β = -3.48, p = 0.007, R2 = 0.58), and ΔSD (β = -0.56, p = 0.046, R2 = 0.35). In women, ΔALI was associated with ΔSD (β = -1.25, p < 0.001, R2 = 0.82) and ΔCDRISC (β = 2.65, p = 0.025, R2 = 0.54). CONCLUSION: Higher allostatic load measured by the ALI is associated with improved sleep quality in both sexes, worsened physical performance in men, and improved resilience in women, highlighting sex-specific responses to military training stress and suggesting that allostatic load may not uniformly contribute to military-specific maladaptation. Supported by: ONR N00014-21-1-2725