You most likely did a push-up at some stage in your life before beginning CrossFit, but you may not have done the full spectrum of motion pushups we use in CrossFit. Your arms should be absolutely straight at the top, and your chest should be in touch with the ground at the bottom.
100 meter Run 10 Muscle-Ups 200 meter Run 20 Handstand Push-Ups 300 meter Run 30 Overhead Squats (45/35 lb bar) 400 meter Run 40 Sumo Deadlift High Pull (45/35 lb bar) 500 meter Run 50 Pull-Ups 600 meter Run 60 Push-Ups 700 meter Run 70 Kettlebell Swings (1/.75 pood) 800 meter Run 80 Burpees 900 meter Run 90 Thrusters (45/35 lb bar) 1,000 meter Run 100 Air Squats