Any part of body, except hands and toes, resting on ground. When maximum number is reached. When resting in up position in excess of 5 seconds. When failing to complete an attempted pushup. Knees bent, feet no further than shoulder width apart.
Touch elbow to knee.
Shoulder blades must ground when down. Elbow not touching knee. Bouncing rear end off ground to gain momentum. Shoulder blades not touching ground when down. After 2-minute time limit or maximum number is reached.