A push-up is a push-up, right? Not so fast — all push-ups strengthen the muscles of the chest, shoulders and triceps, but the degree to which those muscles play a role depends on how you do a push-up.
Modify your push-up so that your hands are higher than your feet at an incline, and put more emphasis on the middle portion of the chest. Place the hands lower than the feet at a decline, and your upper chest and fronts of the shoulders feel the burn.
Incline push-ups primarily target the middle to lower region of the chest, known as the sternal region. They take a little pressure off the fronts of the shoulders and triceps, making them great for anyone who finds a full push-up just too hard.
In a standard push-up, where your feet and hands are parallel to the floor, you resist about 70 percent of your body weight. An incline push-up uses physics to your advantage. When you angle your upper body higher, your lower body supports a greater amount of that weight, so you end up pushing less resistance.
The higher the platform you use for the incline, the easier the incline push-up is to complete. A kitchen counter push-up is much more manageable than a push-up done with your hands on a low stair step.
Because an incline push-up means less resistance, it's also less effective for muscle development if you're capable of doing a regular push-up. Muscle grows in response to stress. The incline push-up may not tax your pecs, shoulders and triceps enough to tear down muscle fibers, so they're prompted to grow bigger. Incline push-ups are usually best reserved as a modification when full push-ups are too hard.
A decline push-up is more intense than the standard push-up. When you place your feet on a plyo box, weight bench or step so that your hands are below your feet, you send more of your body weight into the upper body, taxing the fronts of the shoulders and upper chest, or clavicular region, more than you do during a standard or incline push-up.
An extreme decline, such as a pike push-up or handstand push-up, uses your anterior deltoids -- the fronts of your shoulders -- as the primary muscle. Your upper and lower chest become synergists, or helpers. The pecs still work, but not as hard as they might with a less significant decline or a flat push-up.
Before trying a decline push-up, be sure you can successfully pump out a set of 12 regular push-ups with relative ease. Modify a decline push-up by choosing a very modest angle. Another modification has you support your knees on a stability ball and put your hands on the floor to drive more activation into your shoulders.