Effects of high- vs moderate-intensity exercise on natural killer cell activity

NIEMAN, D. C., A. R. MILLER, D. A. HENSON, B. J. WARREN, G. GUSEWITCH, R. L. JOHNSON, J. M. DAVIS, D. E. BUTTER WORTH, and S. L. NEHLSEN-CANNARELLA. Effects of high vs moderate-intensity exercise on natural killer cell activity. Med. Sci. Sports Exerc., Vol. 25, No. 10, pp. 1126–1134, 1993. The effect of 45 min of high- (80% VO2max) vs moderate- (50% VO2max) intensity treadmill exercise on natural killer cell cytotoxic activity (NKCA) was investigated in 10 well-conditioned (66.0 ± 1.9 ml·kg−1. min−1), young males (22.1 ± 1.3 yr). Blood samples were taken before and immediately after exercise, with three more samples taken during 3.5 h of recovery, and analyzed for proportion of NK cells (CD3-CD16+CD56+) and NKCA. Exercise at 80% vs 50% VO2max resulted in a greater immediate postexercise increase in proportion of NK cells, followed by a 1-h and 2-h decrease below preexercise levels for both intensity conditions. NKCA rose significantly above preexercise levels following high- but not moderate-intensity exercise. For both exercise intensity conditions, NKCA tended to drop below preexercise levels by 1 h postexercise, rising back to preexercise levels by 3.5 h postexercise. When NKCA was expressed on a per-NK cell basis, however, no change relative to preexercise levels occurred following moderate-intensity exercise, while a significant increase occurred after 2-h recovery from high-intensity exercise. These data demonstrate that both high- and moderate-intensity exercise are associated with significant shifts in circulating proportions of NK cells which significantly influence interpretation of NKCA data based on assays using separated mononuclear cells.