Background: While chronic exercise is largely recognized to have beneficial effects on health, the effects of acute exercise on the immune system are hotly debated and remain blurry to some extent. Athletes with life-long experience in exercise training represent an interesting population in that context to investigate potential alteration in the immune response after acute exercise. Typically, exercise intervention studies explore the effects of either endurance or strength exercises on the immune system, with very few studies comparing both exercise types.

Aim: Therefore, this study aims to investigate the impact of life-long exercise history on chosen lymphocytes to an endurance and strength exercise challenge. Three hypotheses were formed. First, it is hypothesized that exercise interventions significantly impact the lymphocyte response. Second, it is hypothesized that different types of exercise interventions (endurance or strength) elicit distinct effects on the lymphocyte response. Third, it is hypothesized that an individual's training history significantly influences the lymphocyte response.

Methods: Twenty-four healthy men were recruited and divided into three groups based on their exercise history: strength athletes (SA), endurance athletes (EA), and controls (C). The study employed a cross-over design, with each participant performing both endurance and strength exercises, separated by a two-month wash-out period. Prior to the interventions, all participants underwent VO2 peak and 1 RM leg tests. Blood samples for immune cell analysis were collected at four timepoints: before exercise, immediately after, one hour post-exercise, and three hours post-exercise. Six specific lymphocyte populations (CD4+, CD8+, double-positive T-cells, NK cells, T-regs, γδ T-cells) were analyzed using mass spectrometry at the Karolinska Institute.

Results: Analysis revealed no significant difference for the type of intervention across all lymphocyte subsets. In contrast, except for CD8+, all immune populations showed statistically significant differences between timepoints. Moreover, separate T-test analysis for each of the 48 timepoints revealed no significant differences between endurance athletes, strength athletes and controls, with four exceptions including the CD8+ and double positive T-cell (DPT) population. 

Conclusion: Key findings of this study indicate that lifelong exercise history has a minimal impact on lymphocyte response, suggesting a general lymphocyte reaction to exercise that is independent of training history. Both strength and endurance interventions had similar effects on lymphocyte dynamics, contrary to expectations. The similar responses to both endurance and strength exercises across the three groups imply potential applications for this exercise protocol in clinical settings to stimulate comparable immune responses.