Harry Gaines, author of "Fitness Beyond 50: Turn Back The Clock" appeared on The Doctors to share with them why staying fit is still so important to him. At 74, the writer has adventures planned for his 80s and 90s, so it's important that he take care of himself, he says.

Gaines continues to ride his bike year-round, and still lifts what he could 15 years ago, according to his website. He wrote his book, full of similar personal testaments from active adults, to encourage others to get and stay fit, too.

Check out the video above for some highlights from Gaines' bucket list.