While at Foothill College, Karl was the coordinator of the Adaptive Fitness Technician Program and Lifelong Learning Institute. He taught disabled students and undergraduates about corrective exercise. In addition to teaching, Karl developed the "Fitness Educators of Older Adults Association" to guide trainers of older adults. Currently Karl is a director at the International Sports Science Association and is on the advisory board of PBS's Sit and Be Fit show.

In his spare time he has spoken at conferences, authored many articles, and written numerous books on topics ranging from water workouts to fitness therapy. He was a frequent guest on both radio and print media on issues pertaining to senior fitness and the disabled.