THE EFFECTS OF INCREMENTAL SUBMAXIMAL EXERCISE ON CIRCULATING LEUKOCYTES IN PHYSICALLY ACTIVE AND SEDENTARY MALES AND FEMALES

To study the effects of exercise on circulating leukocytes and leukocy te subsets, physically active (n = 32) and sedentary (n = 32) male and female subjects were randomly assigned to an exercise or control cond ition. Exercise involved a continuous incremental protocol consisting of cycling for three periods of 6 min at power outputs corresponding t o 55%, 70% and 85% maximal oxygen uptake (VO2max). Blood samples were drawn from a venous catheter at baseline, and at 6 min, 12 min, and 18 min after beginning the exercise and 2 h following completion of exer cise. Resting- and exercise-induced alterations in total leukocytes we re independent of gender and subject fitness level. Relative to baseli ne, each increment in workload resulted in a rapid increase in the num ber of circulating leukocytes. Increases in neutrophils, lymphocytes a nd monocytes accounted for the exercise-induced leukocytosis. With reg ard to lymphocytes, exercise resulted in a significant increase in the number of T cells (CD3(+)), T helper cells (CD4(+)), T suppresser (CD 8(+)) and natural killer INK) cells (CD3(-)/CD16(+)/CD56(+)). The larg est percentage increase occurred in the NK cell population. The CD4(+) : CD8(+) ratio decreased (P < 0.001) throughout exercise due to a larg er increase in the number of CD8(+) cells relative to CD4(+) cells. An exercise-induced neutrophilia, lymphocytopenia, and eosinophelia was observed 2 h into recovery. Exercise resulted in significant increases in plasma epinephrine and norepinephrine levels. There was no indicat ion of a hypothalamic-pituitarty-adrenal response during exercise. The results indicate that the rapid, albeit transient, alteration in the number of circulating leukocytes during and following an acute progres sive incremental exercise test are independent of gender and fitness.