Review on aging, unloading and reloading: Changes in skeletal muscle quantity and quality

Aging and muscle unloading are associated with a decline in muscle mass, structure, force and changes in the mechanical properties of skeletal muscle. There is a perception that reloading restores muscle architecture and function but differences in the regeneration capacity of intra- and extra-cellular compartments, age dependent susceptibility to muscle damage, particularly in the contractile machinery, make it difficult to attribute the main role of the above mentioned components. This review briefly summarizes studies that examine aging skeletal muscle during unloading and reloading. The article highlights changes in muscle mass, structure, extra-cellular matrix (ECM) components, strength, locomotion, adaptability to exercise, peculiarities of protein metabolism, susceptibility to glucocorticoids and recovery of muscle from injury.