A study in the Journal of Cachexia, Sarcopenia, and Muscle revealed that just three days of simulated bed rest resulted in a more than 10 percent loss of muscle tissue and increased fatty infiltration of the muscle.

"Believe it or not, you can start losing significant muscle mass in just five days of inactivity," fitness and nutrition expert JJ Virgin told The Epoch Times. She noted that athletes can see the effects of reduced activity within about three weeks if they don't maintain their workout routines.

Everson A. Nunes, a postdoctoral fellow at McMaster University, noted the variability in muscle loss during inactivity. In an email to The Epoch Times, he said that healthy young individuals can lose about 0.8 percent of muscle per day during a week of leg immobilization.

Nunes said that the primary cause of atrophy is the lack of mechanical stimulus.

"Muscles, tendons, and bones need mechanical stress to maintain size, function, and proper turnover rates," he wrote. The key to healthy muscles, tendons, and bones is continuous breakdown and rebuilding.

Muscle loss can happen during extended periods of bed rest because of illness or injury, leading to disuse-induced atrophy.

"Disuse-induced atrophy will likely affect every person in his or her lifetime, and can be debilitating, especially in the elderly," Sue Bodine, who holds a doctorate in neuromuscular physiology, wrote.

"If you're sidelined due to an injury or stuck in bed, your muscles aren't getting the workout they need to stay strong," Virgin said. Without movement, muscles begin to degrade, resulting in a noticeable loss of strength and function.

Aging and Atrophy

Aging is a significant contributor to muscle atrophy. Our bodies naturally lose muscle mass and strength as we age, a process known as sarcopenia. This decline begins as early as age 30, with muscle mass decreasing by 3 percent to 8 percent per decade, and the rate of loss doubling at about age 60, making it even more challenging to maintain muscle health, according to Virgin.

Even more troubling is the loss of strength and power, occurring twice and three times the rate of muscle mass loss, respectively, according to Virgin. These changes can significantly impact daily activities and overall quality of life.