The diamond pushup is an advanced progression of the standard pushup which increases the demands on the triceps and shoulders.
Get into the standard pushup position with your hands together directly beneath your chest so that index fingers and thumbs are touching to form a triangle or "diamond" shape.
Keeping your core tight, slowly lower your body to the ground. Make sure to keep your elbows tucked in close by your sides so they make a 45-degree angle with your torso. Without altering your hand placement, pause and push yourself back to the starting position.
Do not place your hands too far in front of you. Your chest should touch the triangle at the bottom of the pushup.
Avoid moving hips out of alignment. Instead, keep your core tight and back flat throughout the movement.