Skeletal Muscle Mitochondrial Adaptations to Varying Exercise Intensities

Abstract

Introduction: Mitochondria play a vital role in skeletal muscle function, and their adaptations to exercise are regulated by key proteins like PGC-1α (mitochondrial biogenesis) and mTOR (muscle hypertrophy). Varying training modalities, including endurance, HIIT, resistance, and concurrent training, induce distinct mitochondrial changes.

Methods: A literature review was conducted using PubMed to identify human studies published after 2014 on exercise-induced mitochondrial adaptations. The accepted articles focussed on different training intensities and their effects on the skeletal muscle mitochondria.

Results: Endurance and HIIT training enhance mitochondrial biogenesis and efficiency, increasing oxidative capacity and mitochondrial density. Resistance training improves mitochondrial function to support muscle growth, though its effects on mitochondrial biogenesis are less pronounced. Concurrent training, combining endurance and resistance training, optimizes both mitochondrial adaptations and muscle hypertrophy by activating both PGC-1α and mTOR pathways.

Discussion: Exercise intensity and modality-specific adaptations are regulated by the interaction of PGC-1α and mTOR pathways, with mitochondrial fusion and fission enzymes playing a crucial role in maintaining mitochondrial function. Endurance and HIIT training focus on mitochondrial function, while resistance training primarily addresses muscle hypertrophy. Concurrent training optimally stimulates both PGC-1α and mTOR pathways, offering synergistic benefits for mitochondrial and muscle adaptations. Due to individual variability in response to exercise stimuli, personalized training approaches are crucial for maximal athletic performance.

Conclusion: Mitochondrial adaptations depend on exercise type and intensity. Concurrent training provides a promising strategy to maximize both mitochondrial function and muscle growth. Future research should explore optimal training sequencing and molecular mechanisms to refine personalized exercise programs.