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Your training program also impacts how quickly you detrain and lose muscle. Endurance athletes may experience muscle atrophy slower in part because their muscles are leaner and predominantly slow-twitched muscle fibers compared to power athletes, who predominantly have fast-twitch muscle fibers. For example, the book “Sports-Specific Rehabilitation” reports that endurance athletes such as rowers took up to 12 weeks to lose muscle mass and slow-twitched muscle fibers. On the other hand, power lifters, competitive weightlifters and football players can lose muscle strength as early as two weeks with inactivity.
Muscle loss with an increase of fat in the muscle, also known as sarcopenia, is a common aging process. Because this occurs, the elderly may experience quicker muscle loss or more muscle loss during inactivity compared to younger individuals. A 2009 University of Queensland study found that elderly men and women experienced an increase in sarcopenia after 24 weeks of inactivity. Unlike age, gender has not been shown to influence the rate of muscle loss with detraining.