The influence of exercise modality on the inflammatory response to high-intensity interval training

The effect of exercise on immune system activation and regulation has been well studied in athletes following long-duration exercise and elite events, and across various modalities; however, little work has been performed using shorter-duration, high-intensity protocols and in recreational athletes. This study examined the comparative effects of both treadmill running and stationary cycling, high-intensity interval training (HIIT) on circulating inflammatory biomarkers. A total of 26 young, healthy participants completed both exercise modality protocols in a randomized order using a crossover design. Blood samples were collected at baseline, immediately after exercise, and 1 and 24 h postexercise time points, then processed for cytokine concentrations. Interleukin (IL)-6 increased immediately following both exercise modalities (P < 0.001). IL-8 increased following treadmill running (P = 0.02) and continued to increase during 1 h and 24 h recovery postexercise (P < 0.001). IL-10 increased following 24 h recovery in treadmill running (P < 0.01) and stationary cycling (P < 0.05). There were no significant changes in IL-1ra or tumor necrosis factor α. C-reactive protein trended to increase 24 h after treadmill running with a large effect size (η2 = 0.22). Treadmill running and stationary cycling HIIT provide the necessary stimulus to alter circulating cytokine concentrations. IL-6 and IL-10 increased to the same extent following both exercise modalities. IL-8 was found to increase significantly following treadmill HIIT but not following cycling HIIT. These findings may inform the design of future studies investigating the influence of HIIT on measures of inflammation and health in healthy and clinical populations.