P Shek | PubMed Health

PubMed1992

Immune responses and increased training of the elite athlete.

Ten elite male runners (age, 29.8 +/- 1.7 yr; maximum oxygen consumption, 65.3 +/- 4.9 ml.kg-1.min-1; 10-km times, 31 min 43 s +/- 1 min 46 s) deliberately increased training schedules by an average of 38% for 3 wk. Resting heart rate and maximal oxygen intake were unchanged, but the heart rate response to acute exercise was decreased. Following heavy training, blood samples taken at rest showed trends to a decreased helper/suppressor cell ratio, an increased phytohemagglutinin (PHA)- and concanavalin (ConA)-stimulated lymphocyte proliferation, and a decreased production of immunoglobulins IgG and IgM. Whereas PHA-stimulated lymphocyte proliferation was initially unchanged by acute exercise, after 3 wk of heavy training the same acute exercise caused an 18% suppression of proliferation. Acute exercise following heavy training did not alter pokeweed-stimulated IgG or IgM synthesis. There was no correlation between changes in lymphocyte subpopulations, helper/suppressor ratios, and mitogen-induced cellular proliferation. The immune system of endurance-trained athletes at rest seemed to tolerate the stress of heavy training, but superimposition of a bout of acute exercise on the chronic stress of heavy training resulted in immunosuppression, which was transient and most likely not of clinical significance.

Adult↗

PubMed1991

Physical activity and the immune system.

Methods of examining immune function include a charting of susceptibility to infections, differential blood counts or lymphocyte counts, and measures of cell proliferation and immunoglobulin synthesis in response to external mitogens. The reported acute response to exercise is transient and quite variable, depending upon the type of exercise, the immunological methodology used, the intensity of effort relative to the fitness of the individual, and the timing of observation. A leucocytosis, a granulocytosis, a small lymphocytosis, and a decrease in the proportion of T to B cells reflect mainly changes of blood volume, demargination, and migration of cells. Lymphocyte subsets show a decreased helper/suppressor cell ratio and an increase of natural killer cells. Because of the lymphocytosis, mitogens induce an increased overall cell proliferation, but proliferation for a given number of cells is decreased. Prolonged exercise leads to a decrease of serum and salivary immunoglobulin levels. Soluble factors such as interleukin-1 and interferon are increased by a bout of exercise. Cross-sectional comparisons and training experiments suggest that under resting conditions well-conditioned individuals show some lymphocytosis, increased natural killer cell activity, higher levels of interleukin-1, and possibly an enhanced reaction to mitogens. Moderate training does not greatly change exercise responses at a given fraction of maximal effort. Excessive training suppresses immune function, but the changes are small, variable, and thus difficult to relate to overtraining. Moreover, because of their transient nature, they have only a limited influence upon the risks of infection or cancer.

Exercise↗