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Now let's focus our attention on exercise.

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You know, exercise and nutrition go hand in hand.

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Dr. Don Hagen, the exercise lead in the Human Adaptations and Countermeasures Office

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at NASA Johnson Space Center, can tell us more.

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Hello. Jennifer is correct.

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Good nutrition and exercise are interconnected.

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My job as the exercise lead in the Human Adaptations and Countermeasures Office

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here at the Johnson Space Center is to work with a team of specialists

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to determine the exercise requirements for astronauts in long-duration spaceflight.

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A long-duration spaceflight can be anywhere from months on the International Space Station

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to years if we ever travel to other planets.

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Before I continue, let's take a look at the following questions.

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Why is it important for astronauts to exercise in space?

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Do astronauts have to be elite athletes to endure a long-duration spaceflight?

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Explain.

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What are some of the ways you measure your level of fitness?

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Students, as your teacher pauses the program,

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take a few minutes to answer and discuss the questions with your class.

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When astronauts work in the International Space Station,

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they are working in a microgravity environment.

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They appear to be floating in the ISS.

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The apparent weightless environment places a reduced load on the leg and back muscles.

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Astronauts hardly use their leg muscles in space.

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The lack of muscle activity can cause the muscles to weaken or reduce in size.

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We call this muscle atrophy.

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It is possible astronauts on long missions may lose up to 25% of their muscle mass

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while working in space.

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The loss of muscle mass and strength during these missions

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could pose dramatic problems when they return to Earth.

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Muscles support the bones in your body,

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and if you have a combination of weak muscles and weak bones,

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can you imagine the harmful effects your body could face?

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To prevent muscle atrophy, astronauts must be in good physical condition

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while here on Earth or working in space.

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Do astronauts need to be elite athletes?

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There are no physical requirements to be astronauts

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other than you have to be healthy and pass a physical examination.

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Astronauts perform physical conditioning on a regular basis as part of their training.

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This also applies to them when they are working in space.

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The NASA team is responsible for pre-flight, in-flight, and post-flight

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exercise performance testing for all astronauts.

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We want to make sure astronauts are in good shape before they go into space,

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lose the least amount of muscle mass while in space,

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and rehabilitate their whole body when they return from space.

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We can conduct research to measure the muscle performance of astronauts

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by simulating an apparent weightlessness environment here on Earth.

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Any ideas on how we can do that?

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Exposure to spaceflight is very similar to prolonged bed rest.

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Remember, a cause of muscle atrophy in space is lack of muscular activity.

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That's why bed rest is a good model because it minimizes activity,

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and like astronauts, you lose muscle mass primarily in the legs.

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During prolonged bed rest, the body gradually degrades

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and loses muscle mass, bone mass, and endurance capacity.

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Let's look at an example of how we measure muscle performance.

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Suppose we use Norbert as our test subject and want to measure

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his exercise power output during pre-flight, in-flight, and post-flight.

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In pre-flight, we would first have Norbert use a resistive device

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to measure his leg power.

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As you can see in the animation, Norbert's legs are pretty strong.

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He was able to lift 100 kilograms ten times.

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Next, we simulate in-flight testing by putting Norbert in bed

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for an extended period of time, say 20 days.

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During that period, Norbert conducts all his activities in bed

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except for using the restroom.

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On day 20, we measure his leg power again while in bed

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using the same resistive device

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and see that Norbert can only lift 75 kilograms ten times.

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What percentage decrease in leg power did Norbert lose over the 20 days?

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If you say 25%, then you're right.

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After 20 days, Norbert is removed from the bed

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and the rehabilitation process begins to rebuild his leg muscles.

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This is considered post-flight.

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He undergoes an exercise program that will allow him

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to regain the strength he lost in his legs.

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I'm sure glad he purchased that Galactic Fitness 9000 treadmill.

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In reality, the recovery process is different for most astronauts.

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It takes about 30 days for muscle strength and exercise capacity

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to return to normal,

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but bone density may take six months to a year to return to normal.

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The research we conduct in space and here on Earth

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may one day benefit many populations,

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such as the elderly or people who have had major operations

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and are subjected to extended bed rest.

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The important thing for you is that exercise and good nutrition

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help to build strong muscles, bones, and endurance capacity,

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and that both are needed throughout your life

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in order to optimize your health and thus prolong your life.

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Well, Jennifer, back to you.

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And by the way, how is your friend's exercise and nutrition program coming along?

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Well, I think RJ really understands the importance of good nutrition and exercise

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and that they go hand in hand to maintain good health overall.

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At the beginning of the program,

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do you remember RJ saying that his energy level was pretty low?

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Well, energy fuels growth, movement,

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and all the processes in every cell inside the human body.

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You know, now is a good time to go back and visit our friends

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at the New Mexico School for the Deaf

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to see how they're coming along on their second activity, Your Energy Needs,

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and how it applies to RJ's workout.