Position yourself on all fours. Slightly lift your knees to hover above the ground. Using both your quads and your arms, push body back toward your toes (but remain stationary, feet and arms planted to the ground). When you can go back no further, swing slightly down toward the ground and cycle around back to your starting position. This exercise, while called a “push-up” will be felt in the quadriceps, not the arms.
For advanced modification, cycle forward rather than backward.