Abstract

The effect of 45 min of high- (80% VO2max) versus moderate- (50% VO2max) intensity treadmill exercise on circulating leukocyte and lymphocyte subpopulations, catecholamine and cortisol levels, and the mitogen-stimulated lymphocyte proliferative response was investigated in 10 well-conditioned males (VO2max 66.0+-1.9 ml/kg/min; 22.1+-1.3 yr). Blood samples were taken before and immediately after exercise, with 3 more samples taken during 3.5 h of recovery. Treatment order on the treadmill (graded walking at 7.3+-0.1 km/h, 6.5+-0.6% grade, versus level running at 16.1+-0.3 km/h) was counterbalanced, with subjects acting as their own controls and results analyzed using a 2x5 repeated measures ANOVA. The concanavalin A- (Con A) stimulated lymphocyte proliferative response was decreased at 1 h and 2 h post exercise relative to baseline levels following both exercise-intensity conditions. However, when adjusted on a per-T cell (CD3+) basis to account for the change in number of T cells in the in vitro assay, only the high-intensity exercise condition was associated with a 1-h post-exercise decrease (21%) in the proliferative response relative to baseline. Exercise at 80% versus 50% VO2max resulted in significantly greater increases in cortisol and epinephrine concentrations, providing a physiological rationale for the immediate-postexercise lymphocytosis, 1-to 3.5-h lymphocytopenia, and the decrease in Con A-stimulated lymphocyte proliferative response (per CD3+ cell) that occurred in greater measure after high-intensity work. Verf.-Ref.