If you train hard, you improve the health of your mitochondria, and the intensity (high or low) does not matter much to obtain this benefit.

noli's read

This advice is widely supported by current research, which confirms that exercise is a powerful stimulant for mitochondrial function and density. Robust meta-analyses, including syntheses involving thousands of participants, show that both low-to-moderate intensity endurance training and high-intensity interval training (HIIT) promote significant mitochondrial adaptations. The idea that intensity matters little is, however, nuanced: while both modalities work, they may stimulate slightly different pathways. Training volume is often identified as a determining factor for increasing the number of mitochondria, while intensity may be more effective for improving their functional efficiency. There is therefore no exaggeration, but rather a useful simplification to encourage regular practice, as consistency remains the most critical factor for long-term metabolic health.

the sources

1. 1Rosenblat MA, Perrotta AS, Vicenzino B 2019
2. 2Silva Oliveira P, Boppre G, Fonseca H 2024
3. 3Menshikova EV, Ritov VB, Ferrell RE, et al. 2007
4. 4Milanović Z, Sporiš G, Weston M 2015