Exercise‐induced amplification of mitogen‐stimulated oxidative burst in whole blood is strongly influenced by neutrophil counts during and following exercise

This study characterized the effect of moderate‐ or vigorous‐intensity exercise on leukocyte counts, using fingertip sampling, and mitogen‐stimulated oxidative burst, measured in whole blood with a point‐of‐care test. In a randomized crossover design, 13 healthy adults (mean ± SD age: 22 ± 2 years; seven male, six female) cycled for 30‐min, once at 52 ± 5% [Formula: see text] O(2peak) and on another occasion at 74 ± 9% [Formula: see text] O(2peak). Blood was sampled at baseline, immediately post‐exercise, and 15‐ and 60‐min post‐exercise. The leukocyte differential and mitogen‐stimulated Reactive Oxygen Species (ROS) production were assessed. Lymphocytes increased immediately post‐exercise and decreased below pre‐exercise levels 15‐ and 60‐min later. Lymphocyte mobilization immediately post‐exercise was 59 ± 36% greater with vigorous‐ compared to moderate‐intensity exercise (p < 0.01). Neutrophils increased immediately after exercise (38 ± 19%, p < 0.01) remaining elevated 60‐min later (50 ± 34%, p < 0.01; averaged across intensities) and did not differ between intensities (p = 0.259). Mitogen‐stimulated ROS production was amplified immediately (+32 ± 37%, p < 0.01) and 60‐min post‐exercise (+56 ± 57%, p < 0.01; averaged across intensities) compared to rest and did not differ with intensity (p = 0.739). Exercise‐induced amplification of ROS production was abolished when correcting for neutrophil, monocyte and platelet counts and correlated most strongly with neutrophil mobilization immediately (r = 0.709, p < 0.01) and 60‐min after vigorous exercise (r = 0.687, p < 0.01). Leukocyte kinetics can be assessed using fingertip blood sampling in exercise settings. Exercise‐induced amplification of oxidative burst is detectable with a point‐of‐care test, but results are strongly influenced by neutrophil counts, which may not be routinely quantified.