The results of a recent study suggest that HIIT increases the amount of proteins important for energy metabolism and muscle contraction in skeletal muscle and chemically alters important metabolic proteins. These findings could explain the positive effects of HIIT on metabolism and pave the way for further studies investigating how exercise influences these processes.

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“Exercise has many positive effects that can help prevent and treat metabolic diseases, and this is likely the result of changes in energy use in skeletal muscle. We wanted to understand how exercise alters muscle protein levels and how it regulates the activity of these proteins through a chemical reaction called acetylation,” says Morten Hostrup, first author and co-author of the study and associate professor at the Department of Nutrition, Exercise, and Sports at the University of Copenhagen, Denmark. Acetylation occurs when a member of the group of small molecules, acetyl, combines with other molecules and can influence the behavior of proteins.

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For their study, the team recruited eight healthy, untrained male volunteers who completed high-intensity bike training for five weeks. The men worked out three times a week, cycling for four minutes at a target frequency of more than 90% of their maximum heart rate, followed by a two-minute break. They repeated this pattern four to five times per workout.

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Using mass spectrometry, the team analyzed changes in the composition of 3,168 proteins in tissue samples taken from participants before and after training. They also investigated the changes at 1,263 lysine acetyl sites of 464 acetylated proteins.

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Their analyses showed increased production of proteins, which are needed to build mitochondria, which produce energy in cells, as well as proteins associated with muscle contractions. The team also found increased acetylation of mitochondrial proteins and enzymes, which are involved in cellular energy production. In addition, they observed changes in the amount of proteins that reduce skeletal muscle's sensitivity to calcium, which is essential for muscle contractions.

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The results confirm some known changes in skeletal muscle proteins after training and also point to new ones. For example, reduced calcium sensitivity could explain why muscle contraction may be more difficult following an athlete's fatigue. The work also suggests that training-related changes in the regulation of proteins through acetylation may help to increase metabolism.

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“Using cutting-edge proteomics technology, our study provides new information about how skeletal muscle adapts to training, including identifying new proteins and acetyl sites that are regulated by training,” summarizes co-author Atul Deshmukh, associate professor at the Novo Nordisk Foundation Center for Basic Metabolic Research at the University of Copenhagen. “We hope that our work will inspire further research on how physical activity can help improve human metabolic health. ”