I routinely use the above each and every week with my private training clients. It's a great way to train the core musculature, the chest, shoulders, triceps, etc. It's also a great mental toughness type exercise because of its grueling nature. Think your fit? Try 3 rounds of the above doing 1:00 pillar bridges and 20 push-ups at at a time without stopping to rest, put your knees down, etc. Have fun!