Extended periods of limb immobilization — whether from long-term bed rest, casting, spaceflight, or other circumstances — can reduce skeletal muscle mass and strength to the extent that recovery is delayed or never achieved. The biological basis for this lack of recovery, however, remains unclear. An animal study provides the first evidence that pericytes (cells integral to blood vessel formation) are important for regulating muscle mass, particularly in the context of recovery following disuse atrophy.