Exercise profoundly alters muscle structure and function. It triggers a metabolic and structural remodeling process within skeletal muscles. This leads to several key changes:
Improved Contractile Properties
Exercise strengthens muscles, enhancing their ability to contract and generate force. This is achieved through several mechanisms:
- Increased Muscle Fiber Size (Hypertrophy): Resistance training, in particular, stimulates muscle fiber growth, leading to larger, stronger muscles. This involves increased protein synthesis and a reduction in protein breakdown within muscle cells. https://www.medicalnewstoday.com/articles/319151
- Improved Neural Efficiency: Exercise improves the nervous system's ability to recruit and coordinate muscle fibers during movement. This means you can use more muscle fibers at once, leading to increased strength even before significant muscle growth occurs. https://www.scientificamerican.com/article/how-does-exercise-make-yo/
Enhanced Metabolic Function
Exercise significantly boosts muscle metabolism:
- Improved Insulin Sensitivity: Muscles become more efficient at using glucose (sugar) for energy, improving insulin sensitivity and reducing the risk of type 2 diabetes. https://pmc.ncbi.nlm.nih.gov/articles/PMC5830901/
- Increased Mitochondrial Biogenesis: Mitochondria, the powerhouses of cells, increase in number with exercise, enhancing the muscle's capacity to produce energy (ATP). https://www.nature.com/articles/s42255-020-0251-4
- Reduced Muscle Fatigue: Exercise promotes angiogenesis—the formation of new blood vessels—improving blood flow to the muscles, delivering more oxygen and nutrients and reducing fatigue. https://pmc.ncbi.nlm.nih.gov/articles/PMC4048572/
Impact of Inactivity
Conversely, a lack of exercise leads to the opposite effects:
- Muscle Atrophy: Muscle cells shrink in size due to reduced protein synthesis and increased protein breakdown. https://www.piedmont.org/living-real-change/does-muscle-turn-to-fat-when-you-skip-workouts
- Decreased Metabolic Function: Insulin sensitivity declines, mitochondrial function diminishes, and the muscles' capacity to utilize energy becomes impaired.
Conclusion
In summary, exercise stimulates significant positive adaptations in muscles, improving their strength, size, metabolic function, and endurance. Conversely, inactivity causes muscle loss and metabolic decline.
