I have yet to experience a spinning class that was not challenging to me. It is a different workout however. I love to tour, do 50-120 miles and the spinning class is far different from that. More of an aerobic workout. And it got this novice out of the saddle for extended periods, which helped me over mountain passes and the like. In winter, it's just part of a varied list of activities I do. Basketball, weights, flex, core, skiing. And yes some biking when the weather allows. In the warm months, biking is king and little else for exercise.