Sprint interval exercise disrupts mitochondrial ultrastructure driving a unique mitochondrial stress response and remodelling in men.
Level 2 - randomized trial
Individual randomized controlled trial.
PubMed 41326383 · doi:10.1038/s41467-025-66625-8
What was done
An open-label counterbalanced randomized controlled trial compared sprint-interval exercise (SIE; n = 14) to moderate-intensity continuous exercise (MICE; n = 14) in men. The researchers assessed acute mitochondrial ultrastructure, the unfolded protein response (UPRmt), integrated stress response (ISR), and mitochondrial quality control (MQC) pathways, as well as chronic mitochondrial adaptations following eight weeks of sprint-interval training (SIT) versus moderate-intensity continuous training (MICT).
What was found
The abstract does not report specific numerical values, percentages, or effect sizes. Directionally, acute SIE triggered morphological and structural mitochondrial alterations, a mitochondrial stress signature, UPRmt, ISR, and MQC pathway activation relative to MICE. After eight weeks, MICT increased mitochondrial content and complex I activity with an enrichment of tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS) proteins. In contrast, SIT improved mitochondrial respiratory function, upregulated 1-carbon metabolism and protein quality control pathways, and led to specific accumulation of COX7A2L in III2 + IV1 supercomplexes.
Why it matters
These findings show that exercise intensity selectively dictates mitochondrial adaptations, establishing that high-intensity sprint training induces structural stress and specialized supercomplex remodeling rather than the general increase in mitochondrial content seen with moderate continuous training.
Limits
The sample size was small (14 participants per group), the trial was open-label, and the study was conducted exclusively in men, limiting generalizability to females. The abstract provides qualitative directional findings without reporting exact effect sizes, variance, or p-values.
Cited by
- supports Very vigorous exercise, such as all-out Wingate cycling sprints, can acutely and transiently reduce or impair mitochondrial capacity immediately post-exercise.