With the side-to-side plyo push-up, place one hand on a stable elevated surface and keep the other arm on the floor. As with the all plyo push-ups, the goal is to project yourself explosively. In this variation, you switch hand positions in mid-air. Keep your glutes and abs tight.
Absorb the impact with your elbows at about 90 degrees. Do not lower the chest all the way to the ground.
The right kind of lifting will increase mobility and flexibility better than stretching or goofy mobility drills. And you'll build muscle too. Check this out.