Proinflammatory Effects of Heat Stress in Exercising Marines


Name: Rebecca Phillips

Rank: CDR, USN

Organization: The Geneva Foundation

Performance Site: Officer Candidate School, Quantico, VA; National Naval Medical Center, Bethesda, MD; University of Wisconsin, Madison, WI

Year Published: 2000

Abstract Status: Initial


Heat illness severely impacts the readiness of a military combat unit. As internal temperature exceeds 41 degrees Celsius, central nervous system disturbances, anhidrosis, and rhabdomyolysis are seen. Evidence suggests that exertional heat stroke involves loss of thermoregulatory control and an acute phase reaction to muscle damage. The relationship between the pro-inflammatory cytokine Interleukin-6 (IL-6), severity of rhabdomyolysis and degree of heat illness experienced is not known. In addition, the influence of pre-exercise anthropormorphics, fitness level and hydration status on the occurrence of heat illness and release of IL-6, in the face of endotoxin, is not fully understood. Therefore, study purposes are to identify relationships between (a) pre-exercise hydration, fitness, and anthropometrics, with the occurrence and severity of a heat illness. (b) HSP70 release and translocation of endotoxin with cytokine presence and severity of rhabdomyolysis. In addition, subjects requiring rapid cooling for a heat illness will be assessed for onset, severity and duration of vasomotor activity and shivering to identify their effect on rhabdomyolysis, cardiovascular oxygenation parameters. Specific aims: #1: describe pre-exercise anthropormorphics, fitness level, temperatures and gradients, urine specific gravity, enzymes, IL-6, HSP70, endotoxin, C-reactive protein (CRP), and white blood cell (WBC) differential. #2: compare pre-exercise body weight, temperatures and gradients, urine specific gravity, enzymes, IL-6, HSP70, endotoxin, C-reactive protein, and white blood cell differential with post-exercise values. In subjects who experience a heat related illness: #3: determine existence of relationships between pre-exercise anthropormorphics, fitness level, internal and external temperature and gradients, urine specific gravity, CPK, SGOT, LDH, IL-6, HSP70, LPS, CRP, WBC differential with severity of heat illness. #4: describe the course of enzymes, IL-6, HSP70, CRP and WBC differential over 72 hours post heat illness. #5: in subjects requiring rapid cooling, describe thermal, cardiovascular, and oxygenation responses, changes in cutaneous blood flow, as well as onset, severity and duration of shivering. Differences by ANOVA and Repeated Measures ANOVA, Pearson Product Moment and Spearman rho correlational procedures will test these aims.