Researchers uncover how high-intensity interval training alters inflammatory responses

New research published in ImmunoHorizons shows that running a high-intensity interval training (HIIT) workout triggers a more inflammatory immune response than cycling HIIT. These findings could help everyday athletes make informed decisions about their workout choices to achieve the known anti-inflammatory benefits of exercise while limiting excessive tissue damage.

To date, the effect of exercise on the immune system has not been well studied using the popular HIIT format, despite extensive research on the immune response following long-duration exercise and elite events, such as marathons.

“Our findings will help recreational athletes select their exercise programs to optimize performance and recovery, and maybe even help new athletes stay consistent if they choose less inflammatory exercises,” said Dr. Juliet Moore, assistant professor in the Department of Kinesiology and Applied Physiology at the University of Delaware, and lead author of the study.

Muscle soreness is an important factor influencing exercise adherence, especially in new athletes. According to Dr. Moore, their findings demonstrate that those unaccustomed to aerobic exercise can achieve similar anti-inflammatory benefits from cycling, without the damaging high-impact associated with running.

This is because the study found that cycling versus running HIIT workouts have different effects on the short-term immune response when matched for intensity, cadence, and duration. 

Blood samples were taken from 26 young, healthy participants before completing a HIIT workout consisting of four rounds of 4 minutes at high intensity with 3-minute rest periods.  More blood samples were taken immediately, one hour, and 24 hours after exercise. The blood samples were then analyzed for immune markers called cytokines.

The inflammatory marker IL-8 increased after running and remained elevated through 24 hours of recovery. This increase in IL-8 was not seen after cycling. IL-8 is released by immune cells in response to micro-tears in muscle tissue caused by exercise and likely contributes to prolonged muscle soreness.

For both running and cycling, the cytokine IL-6 increased immediately after exercise and IL-10 increased after 24 hours. IL-6 is associated with energy use and anti-inflammatory effects in exercise. Release of IL-10 by immune cells acts as a feedback loop to turn off inflammation and prevent further muscle damage.

“Given that cycling produced a similar anti-inflammatory effect compared to running, it could be used in exercise programs to achieve the beneficial anti-inflammatory effects of exercise without additional tissue damage,” shared Dr. Moore.

The researchers plan to expand these studies to incorporate additional types of HIIT protocols along with other types of exercise such as resistance training as well as expand to other age groups and clinical populations.

The research article will be available in ImmunoHorizons or you can read more AAI News & Views on May 28, 2026.

Requests for a full copy of the research article and interviews with authors, ImmunoHorizons, or the American Association of Immunologists can be made to kpalmer@aai.org.

About The American Association of Immunologists

The American Association of Immunologists (AAI) is one of the world’s largest organizations of immunologists and scientists in related disciplines. Our mission is to improve global health and well-being by advancing immunology and elevating public understanding of the immune system. AAI members are responsible for some of the most significant biomedical discoveries of the past century, including the development of life-saving cancer immunotherapies, antibody therapies, transplant technologies, and vaccines. We support scientists across the field of immunology through knowledge dissemination, community building, advocacy, and public outreach.

About ImmunoHorizons

ImmunoHorizons is a fully open access peer-reviewed journal committed to advancing the knowledge of immunology and immunology education. ImmunoHorizons is owned by the American Association of Immunologists and published in partnership with Oxford University Press. 

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