Background Paragraph: 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. 
Story: Danny started weight lifting two years ago, he wanted to be bigger. His brother Arnie preferred athletic competitions such as running, so he became a runner.
Which brother didn't increase the efficiency of his cardiac muscle? Which brother didn't increase the size of his muscles? Which brother didn't increase the strength of his cardiac muscle? Which brother gradually increased the size of his muscles? Which brother gradually increased the strength of his muscles? Which brother had fewer skeletal muscles contract against a resisting force? Which brother had more skeletal muscles contract against a resisting force? Which brother increased the efficiency of his cardiac muscle? Which brother increased the strength of his cardiac muscle? Which brother increased the strength of his muscles less?