T.J. Davenport pulls his way to the top of a 100-foot oak during a recreational tree climbing course at Camp Wyman in Eureka, Mo., last month. Such climbs offer good full-body workouts, advocates say.

What's Your Workout: Tree Climbing Ann Koenig is an urban forester for the Missouri Department of Conservation. In her downtime, she's up in the trees -- as a competitive tree climber.

“Rock climbing is not dangerous when beginning but when top roping or bouldering, it could be,” said Brown, who earned college credits by going on a 500-foot climb in Canada. Both Brown and Lankard ...