Answer;
ATP is needed to relax the muscles;
Muscles require more energy even if they are not very active in the moment because ATP or energy is needed for their relaxation.
Step-by-step explanation;
Relaxation of muscles takes place when the stimulation of nerves stops. Calcium is then taken back into the sarcoplasmic reticulum breaking the link between actin and myosin. Actin and myosin return to their unbound state causing the muscle to relax. ATP is involved in displacing actin from myosin head. Therefore; ATP is required for muscle relaxation.