Andy Devaney
For anyone using HIIT to get fitter without spending half their life in Lycra purgatory, new research suggests the bike may offer a gentler route to the same broad anti-inflammatory benefits as running — with less of the inflammatory aftermath that can leave beginners walking downstairs like a retired wicketkeeper.
Researchers from the University of Delaware found that running-based high-intensity interval training triggered a stronger inflammatory immune response than cycling HIIT, even when the workouts were matched for intensity, cadence and duration.
That matters because soreness is not just an inconvenience. For new or recreational exercisers, it can be the difference between building a routine and quietly deciding that the sofa had a point all along.
Why This HIIT Study Matters
High-intensity interval training has become a fixture in gyms, studios and home workouts because it promises a lot in not much time: bursts of effort, short rests, a raised heart rate and the satisfying sense that something useful has happened.
But while exercise science has long studied immune responses after endurance events such as marathons, less is known about how the body responds to HIIT in its more popular, everyday format.
The new research, published in ImmunoHorizons, looked at how running and cycling HIIT affected short-term immune markers in young, healthy participants. The key finding was not that running is bad or cycling is magic. It was subtler, and therefore more useful: different forms of HIIT may place different demands on the body, even when the workout looks similar on paper.
Running HIIT Produced A Stronger Inflammatory Signal
The study involved 26 young, healthy participants. Blood samples were taken before they completed a HIIT workout made up of four rounds of four minutes at high intensity, with three-minute rest periods between efforts.
Further blood samples were collected immediately after exercise, then again one hour and 24 hours later. Researchers analysed the samples for cytokines, immune markers involved in inflammation and recovery.
The inflammatory marker IL-8 increased after running and remained elevated through 24 hours of recovery. That same rise was not seen after cycling.
IL-8 is released by immune cells in response to micro-tears in muscle tissue caused by exercise. In plain English, it is one of the reasons your legs can feel as though they have been cross-examined by a hill.
Cycling Delivered Similar Anti-Inflammatory Benefits
The more encouraging part for recreational athletes is that both running and cycling produced increases in cytokines linked with beneficial exercise responses.
For both types of HIIT, IL-6 increased immediately after exercise. IL-6 is associated with energy use and anti-inflammatory effects during exercise. IL-10 then increased after 24 hours, acting as a feedback loop that helps turn off inflammation and limit further muscle damage.
That makes cycling an interesting option for people who want the fitness stimulus of HIIT without the same high-impact load that comes with running.
“Our findings will help recreational athletes select their exercise programs to optimise 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.
A Useful Nudge For Beginners And Returners
This research is particularly relevant for people starting exercise, returning after a break, or trying to balance fitness with recovery.
Running is effective, accessible and brutally honest. It also involves repeated impact, which can be unforgiving if the body is not used to it. Cycling, by contrast, can deliver a serious cardiovascular challenge while reducing that pounding through the legs.
According to Dr Moore, the findings suggest that people unaccustomed to aerobic exercise may still achieve similar anti-inflammatory benefits from cycling HIIT, while avoiding some of the muscle damage associated with high-impact running.
“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.
Running Is Not The Villain Here
It would be easy, and slightly daft, to turn this into a running-versus-cycling cage fight. That is not the point.
Running HIIT still has obvious value for people training for running performance, field sports, endurance events or general conditioning. The greater inflammatory response may also reflect the specific muscular demands of running rather than some flaw in the workout itself.
But for the average exerciser chasing consistency, cycling HIIT may be the more forgiving gateway. Less soreness can mean better adherence, better recovery and fewer abandoned fitness plans by week two.
In other words, the best workout is not always the one that leaves you dramatically sprawled on the floor. Sometimes it is the one you can repeat.
More Research Is On The Way
The researchers plan to expand the work by studying additional HIIT protocols, other forms of exercise such as resistance training, and wider groups including different age ranges and clinical populations.
That will be important because this study looked at 26 young, healthy participants. Useful, yes. Universal, no.
Still, the takeaway is practical enough: if running HIIT leaves your legs barking for days, the bike may offer a smarter route into high-intensity interval training. You still get the engine working. You may just avoid feeling as though your calves have filed a formal complaint.