Differential Effects of Acute and Chronic Exercise on Human Neutrophil Functions

AB Exercise effects on immunity are highly dependent on exercise intensity, duration, and frequency. Purpose: Because neutrophils play an essential role in innate immunity, we investigated whether acute severe exercise (ASE) and chronic moderate exercise (CME) differentially regulate human neutrophil functions. Methods: Thirteen sedentary young males underwent an initial ASE (pedaling on a bicycle ergometer with increasing loads until exhaustion), and they were subsequently divided into exercise (n = 8) and control groups (n = 5). The exercise group underwent 2 months of CME (pedaling on the ergometer at a moderate intensity for 30 min each day) followed by 2 months of detraining. The control group was abstained from regular exercise during these 4 months. Additional ASE paradigms were performed every month (in the exercise group) or every 2 months (in the control group). Neutrophils were isolated from blood specimens drawn at rest and immediately after each ASE for assaying chemotaxis, phagocytosis, citrate synthase activity, and mitochondrial membrane potential ([DELTA][PSI]m). Additional blood specimens were drawn from the exercise group before and immediately after the first bout of CME to determine the acute moderate exercise (AME) effects on neutrophil functions. Results: The study's results are the following: 1) the initial ASE enhanced chemotaxis and induced [DELTA][PSI]m depolarization; 2) AME did not influence any measured parameter in neutrophils; 3) CME increased chemotaxis, phagocytosis, citrate synthase activity, and [DELTA][PSI]m; 4) the CME effects remained after detraining except phagocytosis; and 5) the ASE effects disappeared after CME and were partially restored after detraining. Conclusions: ASE and CME differentially affected neutrophil functions, whereas AME was ineffective. Moreover, the fact that CME improves neutrophil functions may partially explain why physically active subjects have a low risk of infection. (C)2012The American College of Sports Medicine