Hormonal

Prolonged physical inactivity combined with chronic hypercortisolemia (simulating clinical stress/illness) causes significantly greater loss of lean muscle mass and strength than inactivity alone, driven primarily by a chronic reduction in muscle protein synthesis rather than increased breakdown.

If you are recovering from an injury or illness requiring bed rest, your body's stress hormones (cortisol) will significantly accelerate muscle loss by shutting down protein synthesis. This loss is worse than inactivity alone. While you cannot always avoid the need for rest, recognizing this mechanism highlights the importance of medical interventions that support protein synthesis during recovery, rather than assuming muscle loss is inevitable.