Push-ups are an amazing exercise because they work your whole body. They work the chest muscles and the core muscles at the same time, so a lot of the benefits you get from planks, you get from push-ups.

Push-ups are great for people of any age and fitness level, because they can be modified and changed in difficulty, so you can do easy push-ups on your knees, medium difficult traditional push-ups and very difficult plyometric clapping or one-legged push-ups, all with the same exercise.

But it's also easy to get them wrong — in the IronStrength classes I teach, I see people with their hands too close together, their bodies sagging and yet getting nowhere close the ground.

Here's how to do it better:

Start with your hands slightly wider than your shoulders. This will give you a more full range of motion to lower to the ground.

Keep your core engaged. Think of this as a plank position in motion.

Fight the sag. Your butt should still have some lift to it.

Keep your elbows back and close to your torso.

Lower down to about an inch from the floor. If you can't do this from a plank position, simply try it from your knees.

Push back up, but not too fast! Pause on the way up to really work the muscles.

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Jordan D. Metzl, MD is a sports medicine physician at the Hospital for Special Surgery, author of The Workout Prescription and creator of the IronStrength workout.