Muscle stiffness after a stroke, known as spasticity, happens when damaged brain pathways lose the ability to send normal relax signals. Instead of resting, affected muscles stay in a constant, high-tension state. This leaves arms or legs feeling heavy, rigid, and hard to move, making straightening a joint feel like stretching a thick rubber band. Muscles may flex involuntarily on their own without your control. Over time, this continuous contraction triggers deep muscle ache