The response of leukocyte subsets and plasma hormones to interval exercise.

Aerobic exercise has an established role in modulation of peripheral leukocyte concentrations. However, the effects of intense interval exercise, as employed by athletes in a range of sports, has been given little attention. Eight trained male athletes of mean age (SD) = 31.5 (4.5) yr; VO2max = 64.3 (3.8) ml.kg-1.min-1 undertook an intense interval exercise protocol (treadmill running) to exhaustion. Subjects completed an average of 15.6 1-min efforts. The protocol produced a biphasic leukocytosis: an initial (immediately posttest) leukocytosis resulting from mobilization of lymphocytes (CD3+, CD4+, CD8+, CD16+/56+, CD3+HLA/DR+) (all P < 0.01), with the later (6 h) leukocytosis resulting from mobilization of granulocytes and monocytes (both P < 0.01). This protocol modified significantly the peripheral blood concentration of the hormones cortisol (both total and free), norepinephrine, DHPG, and dopamine (all P < 0.01). Modulation of peripheral leukocyte subsets induced by interval exercise correlated with both the number of exercise efforts performed and the concomitant changes in peripheral hormone concentrations. Sustained alterations in plasma catecholamine levels in the posttest period may have important metabolic and immunological implications for athletes undertaking regular interval training.