Immune function during and after 60 min of moderate exercise wearing protective clothing

As exercise while wearing protective clothing exacerbates body heat storage compared to exercise in the heat, and as exercise alters immune responses, it appeared worthwhile to examine immune and stress responses while wearing protective clothing during moderate exercise.

Eight subjects completed two bouts of exercise at 45% Vo2(max) in a thermoneutral environment: once while wearing shorts only (Control trial, CON) and again while wearing protective clothing (PRO). Venous blood samples were taken to analyze TNF-alpha mRNA by RT-PCR in LPS stimulated blood, plasma catecholamines, and cortisol. Blood cell count was analyzed by flow cytometry. Rectal temperature (T(re)) was monitored continuously.

Exercise with PRO resulted in significantly greater increases in T(re) (39.2 +/- 0.2 degrees C in PRO vs. 38.0 +/- 0.1 degrees C in CON) and plasma epinephrine and norepinephrine (+70% and 150%, respectively). Plasma cortisol increased only at the end of PRO exercise (+33%). Leukocyte and lymphocyte cell count was 14% and 18% higher, respectively, but there were no significant changes in T cytotoxic and NK cell counts compared to the CON trial. Only T helper lymphocyte count was lower (-29%). During both exercise trials, T helper lymphocytes were significantly decreased at the end of exercise and recovery. With or without protective clothing, exercise was associated with an inhibition of TNF- alpha expression in stimulated monocytes (approximately -50% at min 20 and 40, and approximately -30% at min 60).

Protective clothing wearing induces significant thermal challenge during exercise. The inhibition of TNF-alpha appears to be mediated primarily by exercise and not the added thermal load associated with protective clothing.