The Centers for Disease Control and Prevention Director's Physical Activity Challenge: an evaluation of a worksite health promotion intervention.

In 1996, the Centers for Disease Control and Prevention launched a 50-day exercise campaign called the "Director's Physical Activity Challenge" to stimulate its employees to exercise. Of the 5822 eligible employees, 3740 (64%) joined, but pre- and post-data was available on only 1192 (20.5%) people. Of this group, 86% of those in contemplation and 64% of those in preparation, and 34% of those in action advanced to a higher stage.