Narrator: This is Science Today. Muscle atrophy refers to the shrinkage of muscle fiber from lack of forceful exertion. Dr. Kenneth Baldwin of the University of California, Irvine worked with NASA to come up with an exercise routine to prevent this from occurring in astronauts traveling through space. Since muscle atrophy parallels the aging process, Baldwin says their findings can also be applied to the general public - especially those over forty.

Baldwin: What we've learned over the years is that we should be using more activity regimens that are called high force, low frequency - as in lifting against a very heavy object.

Narrator: But how does one know if they're putting enough stress on their muscles?

Baldwin: One simple way is that if you are lifting weights and you can basically generate about ten contractions during one session and by the tenth contraction you can hardly move that object, you are pretty sure that that individual muscle group is being adequately stressed.

Narrator: For Science Today, I'm Larissa Branin.