This is an advanced press up exercise. The exercise incorporates your core whilst strengthening the hip flexors and upper legs.
To perform this particular press up, start in the standard press up position with your palms and the tips of your toes on the floor, your arms straight (don’t lock your elbows), and your back straight as well.
As you begin to lower your body to the floor, lift your right foot off the floor, bend your leg and bring your knee so that it touches your right elbow.
As you press back up, return your right leg back to the starting position. Repeat on the other side.