Relationship between moderate intensity endurance training volume and natural killer cell cytolytic activity

Background. This study was designed to examine the relationship between end urance training volume and natural killer cell (NK) cytolytic activity, We hypothesized that a dose dependent relationship exists between forced tread mill training volume and training induced increases in NK cell cytolytic ac tivity. Methods. Experimental design: female, Swiss Webster mice were assigned to t readmill control (TC) or treadmill trained groups (n=10 per group). Trained mice ran at 12 m per min. (8 degrees grade) for: 15 (EX15), 30 (EX30), or 60 minutes (EX60) per day, five days per week for 11 weeks. Splenic NK cell activity was expressed as median lytic unit (LU), median LU per asialo GM( 1) (AsGM(1)(+)) cell, and median LU per spleen. Results. Median NK activity was not significantly increased by training vol ume, A trend toward greater median LU per AsGM(1)(+) cell was observed in E X30 group versus TC (p=0.1). Training volumes less than or greater than thi s level produced smaller increases in NK cytolytic activity, Conclusions. These data provide preliminary evidence indicating that traini ng induced increases in splenic NK cell cytolytic activity do not exhibit a dose dependent relationship with treadmill training volume.