December 23, 2025, 8:04 pm | Read time: 3 minutes
How training affects cells is determined not only by whether we move at all, but also by how intensely and for how long we do it. A study compared sprint interval training with traditional endurance training in terms of changes in mitochondria—with interesting results.
What was studied? For the study published in the journal “Nature Communications,” an international research group examined how both forms of training affect mitochondria.1
Mitochondria: “Powerhouses of the cells,” which—simply put—convert nutrients from our food into energy for our cells, playing a key role in our body’s energy balance.
For the study, more than 20 healthy men trained three to four times a week for eight weeks. One group completed several short, maximum sprint intervals, following the principle of high-intensity interval training (HIIT). The other group trained with longer, steadier sessions. Researchers then examined muscle samples for cellular changes and adaptations.
Results: Only the sprint interval training triggered short-term cellular stress. The mitochondria were slightly deformed, activating a repair program in the body. This temporary disruption has a positive effect. It resembles a kind of immunization of the mitochondria, making them more resilient over time.
After eight weeks, the mitochondria of the sprint group worked more efficiently and could provide more energy. A special protein acts like an adapter, connecting the individual components inside the powerhouses more closely. They form powerful “super-units,” allowing energy to be produced more smoothly. In contrast, endurance training led to cells producing more mitochondria and strengthening their basic building blocks.
Significance: Sprint interval training and endurance training have different effects, but both improve mitochondria in their own way. Short, intense sprints increase their performance, while longer endurance sessions primarily boost the number and structure of the cell powerhouses. Which training form is sensible depends on personal goals. However, a combination can be beneficial. Mitochondria not only produce energy but also play a central role in metabolism, cell regeneration, and the aging process. Since the study was conducted only with young, healthy men, it remains unclear how women, older individuals, or people with metabolic disorders might respond.
That’s Why I Regularly Do HIIT
“I don’t regularly include sprints in my routine, but I do high-intensity interval training (HIIT). My goal is to improve my maximum oxygen uptake, also known as VO₂max. However, as the study shows, HIIT also has positive effects on mitochondria, which are increasingly becoming a focus of research. An interval training session can be designed for beginners to initially include only several targeted increases in intensity. For example, during a walk, occasionally jog, or during a jog, run faster at times.”
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