Differential patterns of the number and proportion of blood leukocytes following endurance exercise of moderate, strenuous and severe conditions

Abstract

A study was conducted to elucidate the acute effects of endurance exercise on white blood cells by setting three conditions of different intensity and duration; (a) an upper limit of aerobic exercise for health promotion and (b) superior limits within endurance exercise tolerance for untrained persons were prescribed separately for the same healthy untrained male student volunteers (n = 10) at intensities of 85% and 95% of the individual anaerobic threshold (AT) values for 1 h and 1.5 h, respectively, on a bicycle ergometer. In addition, (c) participants in a 100 km marathon race (n = 20) who continued running for 10-13 h were examined. Every condition caused significant leukocytosis due to predominant neutrophilia and, to a minor degree, a significant increase in monocyte number, the magnitude of which depended on the severity of endurance workload and persisted even 1 h after the termination of exercise. Simultaneously microscopic evaluation of blood smears revealed the occurrence of an increased proportion of band neutrophils and a decreased proportion of hypersegmented neutrophils (shift to the left) following exercise in condition (b) but not in (a), suggesting that neutrophils are mobilized partly from the bone marrow reserve to the circulation. On the other hand, peripheral lymphopenia was observed after the termination of endurance exercise. These phenomena closely mimicked the known effects of exogenous glucocorticoid administration, suggesting an association with endogenous stress hormone (cortisol) secretion following strenuous exercise. Based on these findings, it is estimated that the threshold workload intensity at which the prominent neutrophilia is induced following endurance exercise with duration over 1 h would correspond to the level of the individual anaerobic threshold.