Think of this exercise as a push-up that's mostly for your shoulders instead of your chest. It forces the shoulders to work hard to drive your body back using a natural arc and push angle.
The Push-Back Push-Up
Level 1: Drop down, explode straight back, and return to push-up position.
Level 2: Same basic movement, but put your feet up on a braced bench. Your abs will be screaming.
Bodybuilding guru Scott Abel says that training for hypertrophy, size, thickness, density, and shape is not the same as strength training. If the question is how to gain unadulterated muscle mass, is hybrid training the answer?