- New research says that high-intensity interval training (HIIT) can improve your metabolic function or how well your body converts food and drink into energy.
- The study says HIIT workouts can also influence mitochondrial proteins, making muscles more fatigue-resistant.
- You can do HIIT workouts on your bike, in the gym, or at home in under 30 minutes to experience the benefits.
When it comes to optimizing your metabolic function—a.k.a. the process of converting food and drink into energy—just a few weeks of high-intensity interval training (HIIT) may have a profound effect, according to a new study published in the journal eLife. And you can accomplish HIIT workouts while cycling, as well as at the gym or at home.
Researchers in Denmark recruited eight healthy, untrained young men to complete five weeks of high-intensity cycling training. They worked out three times per week, with four minutes of cycling done at a target intensity of about 90 percent of their maximum heart rate, followed by a two-minute rest. They repeated the pattern four to five times per workout. (That’s about 24 to 30 minutes total for the session.)
Collecting tissue samples before and after the training, researchers analyzed changes in the composition of about 3,000 proteins and found an increase in those used to build mitochondria—which produce energy in cells—as well as more proteins related to muscle contractions.
These higher amounts of proteins in skeletal muscle translate to better energy metabolism and muscle function, first author Morten Hostrup, Ph.D., associate professor in the department of nutrition, exercise and sports at the University of Copenhagen, told Bicycling.
“Our study underlines the remarkable adaptability and complexity of our muscles,” Hostrup said. “Only a few weeks of HIIT elicits a broad spectrum of changes in the exercised muscles and the net effect of this is that they become better in metabolic function, in a way that may increase performance.”
There are many forms of HIIT, he added, but all can be done in a similar way to the research here—short bursts of intense exercise done at nearly maximum capacity, followed by a few minutes of active recovery between sets.
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Hostrup said that although they expected HIIT to alter the behavior of muscle proteins, they were surprised HIIT changed the regulation of so many mitochondrial proteins, which affects muscles in ways that can be beneficial, including optimized muscle contractions and less muscle fatigue.
The study does have notable limitations, particularly the small number of participants and testing only men. Hostrup added that the results would likely be similar for women, but there are differences in muscle fiber composition between men and women, and in the responsiveness to various exercise stimuli, which means more research needs to be done to confirm whether these results apply to everyone.
That said, HIIT does seem to provide some notable effects in general, especially compared to endurance training, and the reason for that is stress, study co-author Atul Deshmukh, Ph.D., associate professor at the Novo Nordisk Foundation Center for Basic Metabolic Research at the University of Copenhagen, told Bicycling.
“HIIT imposes much more stress on the body in specific ways than typical endurance exercise,” he said. “This stress triggers a multitude of adaptations in muscle fibers, not only boosting their abilities to metabolize substrates like carbohydrates and fat, but also makes muscle fibers more fatigue-resistant."
In other words, HIIT workouts help to train your muscles to efficiently use carbs and fat for fuel, while also helping you ride for longer without tiring out—making them a workout worthy of a spot on your training plan.
Elizabeth Millard is a freelance writer focusing on health, wellness, fitness, and food.
