Adaptation of skeletal muscle to endurance exercise.
Level 5 - mechanism / opinion, no new human data
Narrative review of biochemical and physiological mechanisms.
What was done
This review synthesizes findings on the biochemical and ultrastructural adaptations of skeletal muscle in response to endurance exercise, such as long-distance running. It examines changes in substrate oxidation (pyruvate and long-chain fatty acids), mitochondrial protein content, respiratory chain components, and enzyme kinetics.
What was found
Endurance exercise increased the oxidative capacity of skeletal muscle homogenates and mitochondrial fractions. Mitochondrial protein content increased by 60%, and cytochrome c concentration doubled. Increases in enzyme activity were selective: certain citric acid cycle and respiratory chain enzymes increased 2-fold, others rose by 35% to 60%, while mitochondrial alpha-glycerophosphate dehydrogenase, creatine phosphokinase, and adenylate kinase did not increase. Electron microscopy demonstrated increases in both mitochondrial size and number, shifting skeletal muscle toward a cardiac-like enzyme profile.
Why it matters
This work outlines the classical biochemical basis of exercise-induced mitochondrial biogenesis and the metabolic remodeling that supports enhanced aerobic capacity.
Limits
The abstract provides a narrative summary without systematic search methods, specified study cohorts, or statistical precision estimates.
Cited by
- supports Training for a marathon can double the quantity of mitochondria in skeletal muscle.