Jacob A. Siedlik, Jake A. Deckert, Trent J. Herda, Joseph P. Weir, FACSM, Philip M. Gallagher & John P. Vardiman

Department of Health, Sport, and Exercise Science, University of Kansas, Lawrence, Kansas

Military training programs are rigorous and involve periods of intense physical activity in a high psychologically stressful environment. Quantifying the interplay between exposure to acute physical and psychological stress events and the lymphocyte subpopulations in the peripheral circulation may aid the development of training strategies for military and first responder personnel. PURPOSE: This study’s purpose is to map the trajectory of the immunoendocrine response to training in the Marine Corps Martial Arts Program. METHODS: 10 male marines (age 20 ±1.4y, body mass 74.76 ± 8.96kg, height 177.5 ± 7.44cm) were recruited for participation. Subjects were observed 3 times during a 9-week period. Serial blood samples for cortisol, norepinephrine (NE), epinephrine (EPI) and absolute CD4+ and CD8+ cells were collected before training and during the recovery period (Immediate Post, 15, 30, 45 and 60min). Variables were quantified using summary measures (area-under-the-curve (AUC), time to peak value and peak value) and analyzed using RMANOVAs. Pearson product moment correlations were calculated. RESULTS: There were no significant differences across visits for any of the summary or baseline measures. EPI (69±46.54pcg/ml, 70.6±46.12pcg/ml, 58.5±42.57pcg/ml), NE (880.3±670pcg/ml, 886.4±353.22pcg/ml, 874.1±578.12pcg/ml), CD4+ (744.4±182.15cells/ul, 944.9±326.46cells/ul, 900.6±217.58cells/ul), and CD8+ (664.8±204.89cells/ul, 939.1±443.69cells/ul, 833±238.8cells/ul) cells all reached peak values immediately post training. Times to peak value for cortisol (22.02±6.71mcg/dl, 20.91±5.92mcg/dl, 19.66±3.85mcg/dl) were 18, 7.5, and 9 minutes for Visits 1-3 respectively. As the time intervals between blood collections were 15 minutes, these are interpreted as a peak between 15-30min for Visit 1 and peaks between 0-15min for Visits 2-3. For Visits 1 and 2, CD4+ and CD8+ cells were significant correlated (.728, p=.017 and .712, p=.021). CONCLUSION: The lack of significant differences in AUC values across visits suggests the subject’s acute physiological responses to the training stress are not attenuated with repeated exposures. The observed decrease in the CD4/CD8 ratio immediately post training is not associated with an immunosuppressive response but is driven by an increase in CD8+ cells. Future research should investigate signaling molecules that may preferentially mobilize CD8+ cells in response to acute stress exposure.

Supported by a grant through the Office of Naval Research.

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