The main objectives of this thesis were to investigate the effects upon leukocyte
trafficking and bacterially-stimulated neutrophil degranulation of a chronic intensive training period in a military population (Chapter 4), a 48 h period of fluid, energy or combined fluid and energy restriction at rest and after exercise in healthy males (Chapter 5) and a 2 h exercise bout with and without additional heat stress in trained male cyclists (Chapter 6). Furthem1ore, a water-immersion technique was used to delineate the thermal effects and associated hom1one and cytokine involvement in neutrophil trafficking and bacterially-stimulated neutrophil degranulation responses after prolonged exercise in healthy males (Chapter 7). Twenty weeks of intensive physical training with periods of sleep deprivation, energy restriction, exposure to environmental extremes and psychological stressors had limited effect on leukocyte trafficking and bacterial-stimulated neutrophil degranulation. During training 48 h periods of recovery and rest were adequate to prevent cumulative decreases in circulating cell counts and neutrophil function. Interestingly, 48 h of either fluid, energy or combined fluid and energy restriction equalling ~90 % of daily energy requirements caused decreases in circulating leukocyte, lymphocyte, CD3+ and CD4'
counts and no alterations in circulating neutrophil counts or bacterial-stimulated
neutrophil degranulation. In this incidence 6 h recovery and re-feeding was adequate to normalise circulating leukocyte and lymphocyte counts.
During 48 h period of energy and fluid restriction it may be a combination of small changes in several immune parameters such as circulating leukocyte and lymphocyte counts that compromise resistance to minor illnesses such as URTI rather than a specific alteration in one immune parameter.
Core temperature does not appear to mediate neutrophil responses to prolonged
exercise. Bacterial-stimulated neutrophil degranulation decreased after prolonged cycling and deep water running regardless of heat stress and thermal clamping. This decrease appears not to be associated to activation status (CD 11 b ), band cell counts, cortisol, Granulocyte Colony Stimulating Factor (G-CSF) and Interleukin (IL)-6). It would appear that when athletes and military personnel are not clinically immune deficient, it may still be possible that the combined effects of small changes in several immune parameters may compromise resistance to minor illnesses such as URTI.
Despite some limited findings in this thesis it should be recommended to athletes and military personnel to avoid overtraining, providing adequate rest and recovery during the training cycle and after competitions, limiting exposure to sources of infection, ensuring adequate nutrition, and limit the exposure to environmental extremes such as heat will all help to maintain leukocyte cell counts and neutrophil function.