Activation of natural killer cell function in recreational athletes with paraplegia during a wheelchair half-marathon race

OBJECTIVE: To investigate a part of the immune homeostasis in recreational athletes with spinal cord injury (SCI) during and after a wheelchair half-marathon race. DESIGN: Case-control study in an actual race. SETTING: The half-marathon division of an international wheelchair marathon race in Japan. PARTICIPANTS: Seven male wheelchair racers with SCI between T7 and L1. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Changes in the number and function of natural killer (NK) cells and the endocrine effects, including plasma catecholamines and cortisol in blood samples obtained the day before the race, immediately after it, and 1 day after the race. RESULTS: Both the percentage and absolute number of peripheral NK cells did not change significantly throughout the experiment. Mean NK cell cytotoxic activity +/- standard deviation increased significantly, from 45.5%+/-7.5% to 56.1%+/-5.1% (P<.01) immediately after the race and remained increased until the next day. Plasma adrenaline levels were increased (P<.05) immediately after the race and recovered 1 day later; the plasma concentration of cortisol did not change throughout the experiment. CONCLUSIONS: The wheelchair half-marathon race induced activation of NK cell function in recreational athletes with SCI between T7 and L1.