75Immobilization Causes Rapid Muscle Strength Loss and Atrophy
This systematic review analyzed data from 318 healthy adults across studies of bed rest lasting 5 to 120 days to quantify how quickly muscles weaken and shrink during inactivity. The researchers found that muscle strength declines rapidly during the earliest stages of immobilization, with the greatest rate of loss occurring in the first few days. Notably, strength declined much faster than muscle size, with strength loss outpacing atrophy by a factor of 4.2 on day 5. Approximately 79% of strength loss could be explained by muscle atrophy, while the remainder was due to neural and cellular changes. These findings demonstrate that even short periods of inactivity can significantly weaken muscles, supporting the need to maintain circulation and prevent atrophy during recovery from injury.