How is it poor form if it is used to get a 500lb bench press!!? During any exercise, you want your whole body tight, not just one part of your body. If your body is in a relaxed state, you won't be able to preform well. Doing pushups with just your arms is stupid, you'll only be able to bang out like 15 for one set. However, if you utilize your abdominals, lower back, and upper back, you'll be using your entire body to preform a movment. Now, I don't know about you, but I'd rather use my whole body to move my body, rather than just my arms to move my entire body.