In exercises such as weight lifting, skeletal muscle contracts against a resisting force (see Figure below ). Using skeletal muscle in this way increases its size and strength. In exercises such as running, the cardiac muscle contracts faster and the heart pumps more blood. Using cardiac muscle in this way increases its strength and efficiency. Continued exercise is necessary to maintain bigger, stronger muscles. If you don’t use a muscle, it will get smaller and weaker—so use it or lose it.
Ann loves running. She ran five miles every day until she broke her leg. After that she had to wear a cast for 2 months . When the cast was removed Ann tried to walk and realized that she could not.
Where Ann's cardiac muscles more efficent before or after she broke her leg?