Comparable neutrophil responses for arm exercise and intensity-matched leg exercise

Introduction: Arm exercise is performed at lower absolute intensities than lower body exercise. This may impact on intensity dependent neutrophil responses and it is unknown whether individuals restricted to arm exercise experience the same changes in the neutrophil response as found for lower body exercise. Therefore, we aimed to investigate the importance of exercise modality and relative exercise intensity on the neutrophil response. Methods: Twelve moderately trained males performed three 45-min constant load exercise trials following determination of peak oxygen uptake for arm exercise (V̇O2peak arms) and cycling (V̇O2peak legs): (1) arm cranking exercise at 60%V̇O2peak arms; (2) moderate cycling at 60%V̇O2peak legs; and (3) easy cycling at 60%V̇O2peak arms. Results: Neutrophil numbers in the circulation increased for all exercise trials, but were significantly lower for easy cycling when compared with arm exercise (P=0.009), mirroring the blunted increase in heart rate and epinephrine during easy cycling. For all trials, exercising heart rate explained some of the variation of the neutrophil number 2h post exercise (R=0.51-0.69), epinephrine explaining less of this variation (R=0.21-0.34). The number of neutrophils expressing CXCR2 decreased in the recovery from exercise in all trials (P<0.05). Conclusion: Arm and leg exercise elicits the same neutrophil response when performed at the same relative intensity, implying that populations restricted to arm exercise might achieve a similar exercise induced neutrophil response as those performing lower body exercise. A likely explanation for this is the higher sympathetic activation and cardiac output for arm and relative intensity matched leg exercise when compared with easy cycling, which is partly reflected in heart rate. This study further shows that the downregulation of CXCR2 may be implicated in exercise-induced neutrophilia.