The effect of intense interval exercise on selected immunological, haematological and endocrinological parameters in trained male subjects

Abstract

Exercise has an established ability to alter human physiological systems. However to this time much of the research in this area, and particularly that in relation to the human immune system, has focused on exercise that has required predominantly aerobic metabolism. Little research has been carried out into the physiological effects of intense interval exercise, commonly used as a training regime by athletes in sports such as track & field, ball sports and swimming. This study investigated the effects of intense interval running on selected physiological parameters, with special reference to the immune system and the function of neutrophils. Trained male subjects performed intense interval running protocols both in the laboratory and on a 400 metre running track. The protocols required significant anaerobic energy production as indicated by the elevated post-exercise whole blood lactate concentrations of 7.6 mmol.L-1 and 14.0 to 16.0 mmol.L -1 relating to the laboratory and "track" running protocols, respectively. Intense interval exercise induced a series of biochemical and morphological changes consistent with the multi-faceted activation of neutrophils. Such activation in vivo may have important implications for both tissue damage induced during, and immunocompetence immediately after, intense interval exercise. A single session of intense interval exercise produced significant perturbation of other physiological systems known to be capable of .altering immune function. This was manifested as a significant elevation in the plasma concentrations of several hormones, minor fluctuations in plasma cytokines concentrations and iron status parameters as well as a characteristic pattern of leucocyte mobilisation. After exercise neutrophils displayed phenotypic changes characteristic of activation in vivo. The plasma concentration of elastase (derived from the primary granules of neutrophils) was elevated significantly at 1 hr post-exercise (p<O.OS), while the expression of complement receptor 3 (:::R3;CD11b/CD18), a ts2-integrin stored intracellularly in association with the secondary granules, was increased significantly after exercise (p<0.01). These changes imply that degranulation of neutrophils in vivo was induced by intense interval exercise. Neutrophil expression of LECAM-1, a member of the selectin "family" of cell adhesion molecules, was significantly decreased after exercise (p<0.01). Neutrophils isolated after exercise showed a reduced ability to generate ROS when stimulated in vitro with phorbol myristate acetate (PMA) and opsonized zymosan (OZ), as assessed by both reduction of ferricytochrome c and by luminol-enhanced chemiluminescence, respectively (both p<O.OS). A key component of the neutrophil's NADPH-oxidase system, p47-phox, translocated to the plasma membrane during exercise. The reduced ability of neutrophils isolated after intense interval exercise to generate ROS appears to constitute a post-exercise "refractory" period and be secondary to both assembly and activation of the NADPH-oxidase system during exercise. Increased plasma concentrations of immunosuppressive hormones cortisol and epinephrine during and after intense interval exercise may accentuate the post-exercise refractory period induced after this form of exercise. Our findings indicate that intense interval exercise induced a multi-faceted activation of neutrophils in vivo and imply that both the increased susceptibility of athletes to infection during and after periods of intense competition and training, and tissue damage induced by exercise may be due to activation of neutrophils in vivo during exercise.