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To evaluate if exhaustion after maximal exercise suppresses the immune system; ten healthy male oarsmen (maximal oxygen uptake, 5.7 +/- 0.2 l.min-1; mean and SE) performed a six minute "all-out" bout on a rowing ergometer (394 +/- 12 watt). Rowing increased the blood leucocyte count as reflected in the concentrations of lymphocytes, monocytes, and neutrophils. Two hours after rowing the leucocyte and neutrophil numbers remained elevated, while the lymphocyte count decreased below the prevalue. The concentrations of cluster designation CD3+ (pan T), CD4+ (T subset), CD8+ (T subset), CD19+ (B cells), and CD16+ natural killer (NK) cells increased during rowing with the elevation in CD16+ cells being sevenfold. Only the concentration of CD3+ and CD8+ cells decreased below prevalues two hours after exercise. The lymphokine activated killer (LAK) cell activity of blood mononuclear cells (BMNC), and the NK cell activity of BMNC (%lysis per fixed number of BMNC), either unstimulated or stimulated with interleukin-2, interferon-alfa or indomethacin, also increased in response to rowing, and returned to the prevalues after two hours. In contrast, the BMNC proliferative responses did not change significantly. The evaluation of NK and LAK cell activities, and the proliferative responses of BMNC suggest that six minute maximal exercise does not suppress the immune response during recovery, even when a large muscle mass is involved.

This study evaluated whether the reduction of the neutrophil oxidative burst by N-acetylcysteine improves pulmonary gas exchange during a six minute maximal ergometer row. Healthy trained oarsmen were double-blinded randomized to either N-acetylcysteine (6 g daily for three days) or placebo groups. As determined by the relative changes of the zymosan-stimulated luminol-enhanced chemiluminescence response, N-acetylcysteine suppressed the exercise-induced enhanced neutrophil oxidative burst response to rowing (-7 +/- 6% vs. 17 +/- 8%; P0.05). This was the case although the concentration of neutrophils remained similarly elevated above the pre-exercise level in both trials (to 5.4+/-0.5 vs. 5.9+/-0.6 x 10(9) cells x l(-1), respectively, P0.05). In the placebo and N-acetylcysteine groups, pulmonary ventilation increased and the arterial CO2 partial pressure decreased to the same extent during exercise. Also, at the end of exercise the arterial O2 partial pressure (77 1 vs. 78+/-1 mmHg), haemoglobin O2 saturation (92 +/- 1% vs. 93 +/- 1%) and O2 uptake (5.0 +/- 0.2 vs. 4.9 +/- 0.21 x min(-1)) were not significantly affected by N-acetylcysteine. Equally, two hours after exercise, the pulmonary diffusion capacity was reduced by 7 +/- 2% below the pre-exercise with no significant influence of N-acetylcysteine. We conclude that the neutrophil oxidative burst to exercise does not influence pulmonary gas exchange during and after maximal rowing.

It is not clear how the immune system is modulated in response to physical stress (e.g. trauma, surgery, burn and sepsis). In order to better understand the stress-induced immune changes, effects of isolated stressors are evaluated. Human experiments include hypoxia, head-up tilt, hyperthermina and exercise, which influence all lymphocyte subtypes and especially so the natural killer (NK) cells. In essence, the immune response is enhanced even by light physical stress, but suppressed after prolonged, intense stress.