I have been training for years and have found that any court game starting with pickle ball, tennis, etc., are fun and healthy aerobic workouts. In a gym situation I believe that the stair climber is the best. Not only is the person getting great aerobic movement, your buttock will be happy as well. I try to put my weight on my heels on a stair climber and definitely not on the toes.

Swimming and water aerobics are the only exercise routines I am permitted. I swim 3 days a week, 30 minutes or 60 laps in a 20 yd pool followed by 30 minutes of alternating deep water cross country skiing and water running followed by water walking in chest deep water forward, backward, sideways, etc. Three days I do 60 minutes of water aerobics and 15 to 30 minutes of a variety of deep water exercises before water aerobics class starts.

The first was on a trampoline, and the second on a treadmill, (not running because of asthma since childhood), bicycle is another good way.