Narrator:       This is Science Today. Imagine being well into your 70s and still having the muscle tissue of a 20-year old? Scientists at the University of California, Berkeley have discovered clues about what makes human muscle age. Irina Conboy, who led the study, says they've discovered biochemical pathways linked to the aging of human muscle and by manipulating these pathways in the lab, they were able to restore muscle's ability to repair and rebuild itself.

Conboy:         When people grow old, only some cells are actually old and worn out. But other cells, which are called adult stem cells, remain relatively young and they could replace the aged tissue or aged body with brand new one.

Narrator:       The promise of their discovery is not a fountain of youth, but rather prolonging quality of life.

Conboy:         A lot of the loss of independence, which is brought about by the aging process is because muscle does not work very well and muscle declines. So, people lose strength and agility. It's one of the first and most devastating aspects of aging.