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Hi, Mr. Shepard.

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Hi, you must be Tony. I understand you have some questions for me.

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Yes, our friend Jacob quarantined himself in the treehouse to avoid getting sick,

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but we don't think that's a very good idea.

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Isn't exercise important for staying healthy?

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Yes, exercise is very important in maintaining a healthy body.

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As the lead astronaut strength, conditioning, and rehabilitation specialist

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here at Johnson Space Center, my main responsibility is to design and implement

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strength and conditioning programs for the astronaut corps

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so they can remain healthy here on Earth and in space.

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Astronauts exercise in space?

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Yes, but it begins here on Earth.

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There are three segments to the astronaut fitness program.

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First, there is the pre-flight training phase,

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where we work on improving the astronauts' weaknesses and enhancing their strengths.

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With only microgravity in space, why do astronauts have to be strong?

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Sometimes astronauts need to perform an extravehicular activity, or EVA for short.

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This is where they go outside the spacecraft

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and sometimes work on a satellite or the space station.

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An EVA is very strenuous work, and it requires a lot of strength.

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What is the second segment of training?

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Well, the second segment is in-flight training,

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where the astronaut focuses on maintaining or increasing their level of fitness

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and limiting their physiological losses.

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What are physiological losses?

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Living in a microgravity environment can cause bone and muscle loss,

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a reduction in cardiovascular responses,

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and a decrease in the neuromuscular system.

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Exercise can help decrease those losses

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and can even make you feel better mentally by increasing your endorphins or your happy hormones.

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Why does your body lose bone and muscle in space?

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In a microgravity environment, everything is floating, including yourself,

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and it makes living pretty easy since you don't have to lift, pull, or push very much.

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Therefore, the body tells itself that it doesn't need to keep the muscles strong or the bones dense.

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And the heart figures out that it doesn't need to work very hard

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since the blood can float where it needs to go.

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How do astronauts exercise in space?

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On the International Space Station, there is a cycle ergometer, a treadmill, and a weight-lifting device.

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Astronauts exercise about two and a half hours a day.

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Wow, that must help.

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Exercise is very important in maintaining a healthy body and a good mental attitude at all times.

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Thank you, Mr. Shepard. You've given us a lot of information.

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You're welcome, and call if you need any help putting together a fitness program for Jacob.

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NASA Jet Propulsion Laboratory, California Institute of Technology