Background: 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.

Situation: Jane decided to get in shape for the summer. She went to the gym and started jogging on the treadmill everyday. She also lifted weights a couple days a week.

Question: are janes muscles getting bigger or smaller?

Situation: Jane decided to get in shape for the summer. She went to the gym and started jogging on the treadmill everyday. She also lifted weights a couple days a week.

Question: are janes muscles getting more or less efficent?

Situation: Jane decided to get in shape for the summer. She went to the gym and started jogging on the treadmill everyday. She also lifted weights a couple days a week.

Question: Is jane's heart getting stronger or weaker?

Situation: Jane decided to get in shape for the summer. She went to the gym and started jogging on the treadmill everyday. She also lifted weights a couple days a week.

Question: Is janes body able to pump more or less blood?

Situation: 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.

Question: Where Ann's cardiac muscles getting weaker or stronger when she was running?

Situation: 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.

Question: Where Ann's cardiac muscles getting weaker or stronger when she was not able to run?

Situation: 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.

Question: Were Ann's leg muscles getting weaker or stronger when she was running?

Situation: 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.

Question: Were Ann's leg muscles getting weaker or stronger when she was not able to running?

Situation: 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.

Question: Where Ann's cardiac muscles more efficent before or after she broke her leg?

Situation: 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.

Question: Where Ann's leg muscles bigger before or after she broke her leg?

Situation: 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.

Question: Where Ann's leg muscles smaller before or after she broke her leg?

Situation: 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.

Question: Where Ann's leg muscles weaker before or after she broke her leg?

Situation: 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.

Question: If an walks everyday will her leg muscles gat stronger or weaker?

Situation: 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.

Question: If an doesn't walk will her leg muscles gat stronger or weaker?