EFFECTS OF EXHAUSTIVE ENDURANCE EXERCISE AND ITS ONE-WEEK DAILY REPETITION ON NEUTROPHIL COUNT AND FUNCTIONAL STATUS IN UNTRAINED MEN

Whereas endurance exercise is known to induce marked neutrophilia, it remains to be fully understood as to whether the cell functions are al tered as well as whether the adaptability of the responses to training occurs. To address both of these issues, we undertook the present lon gitudinal investigation in ten healthy untrained men (20-24 years, VO( 2)max 39.1 +/- 4.2 ml/kg/min). The exercise protocol was 7 consecutive sessions of the same workload performed each day for 1.5 h at an inte nsity of 70 % of VO(2)max. Peripheral blood samples were obtained befo re, immediately after, and 1 h after exercise on Days 1, 4, and 7, and served for determination of total and differential leukocyte counts, chemotaxis and chemiluminescence of neutrophils. Acute endurance exerc ise caused marked peripheral neutrophilia with significant increase in both absolute number and relative proportion of band neutrophils (p < 0.01, respectively), indicating partial recruitment of bone marrow ne utrophils. While chemotaxis remained unaltered following exercise, rea ctive oxygen species generation of neutrophils, measured by luminol-de pendent chemiluminescence upon stimulation with opsonized zymosan, was not only significantly enhanced following exercise (p < 0.01), but al so associated with the proportional increase in band neutrophils (r = 0.727, p < 0.05), suggesting that neutrophils mobilized from the bone marrow following endurance exercise may possess higher responsiveness. On the other hand, the magnitude of the exercise-induced changes was reduced gradually by daily repeated exposure to endurance exercise, bu t none of the trends were significant except the decline in resting se gmented neutrophil counts (p < 0.05) at least during a 1-wk period of repeated exercise sessions.