Document Type : Review Article
Authors
1 Professor, Department of Sport Sciences, Faculty of Humanity sciences, Lorestan University
2 MSc. in Exercise Physiology, Faculty of Humanity Sciences, Lorestan University, Lorestan, Iran.
Abstract
Skeletal muscle has a high plasticity in adapting to stressors such as contractive activity (strength training, endurance training, electrical and neuromuscular stimulation), loading conditions (unloading, diseases, lack of movement, and spaceflight), and interventions and environmental factors (hypoxia). Existing evidence shows that skeletal muscle fibers have a unique ability to remember their previous chronic contractile activity and in response to the training period, even after a prolonged lack of training, show faster growth. Scientists have called this phenomenon muscle memory. Primary studies attributed this phenomenon to motor learning through the central nervous system, but subsequent studies suggest that muscle memory may be associated with the content of skeletal muscle nuclei. Although the biological basis of muscle theory is not established correctly, one of the possible mechanisms is that the primary period of exercise training leads to an increase in myonuclei and these nuclei remain stable even after a long period of detraining in skeletal muscle. Therefore, following the retraining period, a muscle whose nuclei have increased in the initial training period can grow more efficiently and show a faster hypertrophy response. However, later studies showed that myonuclei might not be stable and may be destroyed after periods of detraining. Therefore, recent studies investigated other mechanisms such as epigenetics in justifying the theory of muscle memory. In general, the available evidence does not support the stability of myonuclei in the theory of muscle memory, and it is suggested that other evidence such as epigenetics be examined by researchers to justify this theory.
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