Acute high-intensity exercise enhances T cell proliferation compared to moderate-intensity exercise.

Conventional belief is that high-intensity (HI) exercise inhibits immune function; however, recent work challenges this position. The purpose of this was to quantify changes in T cell proliferative capacity following either a HI or moderate-intensity (MI) exercise. Sixteen males were randomly selected to a HI or MI exercise group. Blood was obtained baseline and immediately, 1, 4, and 6 h post-exercise for analyses of CD3⁺ T cell proliferation (co-stimulation via phytohaemagglutinin or CD3 + CD28). The proliferative response increased in T cells in the HI group and remained significantly elevated up to 6 h post-exercise in both co-stimulation conditions. In contrast, the MI group saw no change proliferative ability following exercise. Analyses of serum stress hormones, and immunomodulatory cytokines failed to reveal any correlated variations that could clarify the T cell findings. We suggest the increase in proliferative capacity following HI exercise is indicative of an exercise-induced activation that provides for enhanced functional responses to stimuli. Moreover, this study shows that HI exercise increases T cell processes, effectively priming them for activation in response to stimuli. This study is registered with ClinicalTrials.gov (NCT06638684).