I've been working hard on my push ups lately. It's not an exercise that comes easily to me. I'm still doing them with my hands elevated to make them easier, although I've substantially decreased the amount of elevation over the past year. A couple of weeks ago, I actually managed to grind out 10 good reps using one of the plyo boxes at my workplace gym to elevate my hands.
Yesterday, I was at Planet Granite, and the Smith machine happened to be free. (A Smith machine is basically a barbell on rails that you can lock so that the bar won't travel downward past a certain point. Theoretically, its purpose is to allow people to squat and bench press heavy weights without any danger of dropping the weight on themselves. In practice, its use for this is controversial, because it forces the bar to travel in a straight line, and the human body doesn't really operate in straight lines. But I digress. Smith machines make great adjustable incline push up, inverted row, and pull up machines.)
So, I locked the bar at about the height of the plyo box I've been using, grabbed the bar, and was surprised to discover that I could do 12 reps easily. I lowered the bar a few inches and did a couple more sets in the 6-8 rep range.
While it's possible that I've made a sudden drastic jump in strength, I think that what's actually happening there is that the action of grabbing the bar actually produces a little extra activation in my triceps, deltoids, and pectorals, effectively making me stronger than when I do pushups with my hands flat on a box. It's pretty easy to demonstrate this activation - clench your hand in a fist, and you'll notice that the muscles in your upper arm tense up. I had no idea that it could make such a dramatic difference in strength, though.
This poses an interesting question - will I make faster progress with pushups if I use the bar to elevate my hands, thus achieving greater muscle activation? Or will it be better in the long run to use the box, and try to learn to consciously activate the muscle fibers that I'm unconsciously activating when I use the bar?
(In practice, I'll probably use whichever is most convenient or not in use by someone else. But it's an interesting question.)