How fast will muscle atrophy occur when you stuck in bed from an injury?

Strength loss first. It is amazing how quickly lack of activity can impact the body. Muscle weakness, and even loss of muscle mass is a common and quick effect of illness and being bedridden. I warn patients that for every day in bed especially if critically ill, it can take 4 days of therapy to regain strength to the previous level. Activity is so important for overall and muscle health!