| Summary: | Exercise-induced muscle damage may alter the availability of glutamine for cells of the immune system following strenuous exercise. However, little is known about the effects of exercise-induced muscle damage on the immune system. Elevated serum CK activity, an indirect marker of muscle damage, was used as a post-exercise criterion to place subjects who performed the same exercise into High and Low CK groups. The purpose of this investigation was to determine whether (1) the response of plasma glutamine concentration; and (2) cellular components of the peripheral blood, particularly leukocyte numbers and subset proportions, responded similarly to high force eccentric in High and Low CK groups. Twelve female subjects performed high-force eccentric exercise using one arm and one leg, respectively. Blood samples were collected 1 d and 0 h pre-exercise, 0 and 2 h, 1, 2, 3, 5, 7, and 9 d post-exercise and analyzed for serum CK activity, whole blood glutamine concentration, complete blood count, and lymphocyte subsets consisting of T, CD4+, CD8+, B, NK, and IL-2 receptor positive (IL-2R+) lymphocytes. Seven subjects were placed in the High CK group and 5 in the Low CK group. Differences between High and Low CK groups, identified by comparing the positive and negative integrated areas of deviation from baseline, respectively, were not apparent. For all subjects combined into a single group, there was a 13% increase in granulocytes 0 and 2 h post-exercise, 24 and 29% increases in NK cell concentration and proportion of lymphocytes immediately post-exercise, a delayed increase in NK cells 3 and 9 d post-exercise, and 17 to 22% decreases in CD8+ lymphocytes 2, 5, and 9 d post-exercise (p $<$ 0.05 for all). A significant decrease in blood glutamine concentration (p $<$ 0.05) was measured 3 d post-exercise. These changes were either the result of changes at the level of the muscle induced by the exercise, but independent of factors contributing to CK efflux, or the result of as yet unidentified systemic signals initiated by the performance of the exercise.
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