This push-up variation targets the backs of the arms like no other. To modify, Joel suggests starting on your knees and bringing your knees closer underneath your hips, and building up to doing it starting from a plank.
Begin in plank position with your arms and body straight, shoulders over your wrists. Keep your core engaged.
Bend your elbows behind you and lower your chest to the floor. Keep your upper arms tight to your body so your elbows are against your ribs on both sides.
Straighten your arms, coming back to plank position.
This counts as one rep. Do as many reps as you can with correct form.