Lymphocytes and NK cell activity during repeated bouts of maximal exercise

Effects on the immune system of 6-min ''all-out'' ergometer rowing were investigated over 2 days (2 x 3 bouts) in eight male oarsmen with a maximal oxygen uptake of 5.5 +/- 0.1. l/min (mean +/- SE). Blood samples mere obtained before, during, and 2 h after each bout and on the day after the last bout. Compared with levels at rest, the first bout of exercise increased the concentration of leukocytes (2-fold); neutrophilic granulocytes (2-fold); lymphocytes (2-fold); monocytes (a-fold); the blood mononuclear cell (BMNC) subsets CD3(+) (2-fold), CD4(+) (2-fold), CD8(+) (3-fold), CD16(+) (8-fold), CD19(+) (2-fold), and CD14(+) (2-fold); the NK cell activity (2-fold); and plasma interleukin-6 (3-fold) (P < 0.05). During the last bout even higher levels were noted for leukocytes (3-fold); neutrophilic granulocytes (3-fold); lymphocytes (4-fold); the BMNC subsets CD4(+) (3-fold), CD8(+) (5-fold), CD16(+) (13-fold), CD19(+) (5-fold), and CD14(+) (3-fold); and for the NK cell activity (4-fold) (P < 0.05). During the recovery periods all values were at or above the level at rest, and elevated concentrations of leukocytes (38%), neutrophilic granulocytes (48%), and lymphocytes (46%) reflected in the BMNC subsets and increased NK cell activity (119%) were also noted on the day after the last bout (P < 0.05). The results show that maximal exercise with large muscle groups provokes higher immune responses during repetitive bouts.