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

This study characterised 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 randomised crossover design, thirteen healthy adults (mean +/- SD age: 22 +/- 2 years; seven male, six female) cycled for 30-minutes, once at 52 +/- 5% V̇O_2peak and on another occasion at 74 +/- 9% V̇O_2peak. Blood was sampled at baseline, immediately post-exercise, and 15- and 60-minutes 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-minutes later. Lymphocyte mobilisation 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.