<iframe src="https://player.vimeo.com/video/272879349?background=1" width="640" height="360" frameborder="0" allowfullscreen></iframe>
Grab two dumbbells and lay on your back on a bench with your shoulders up and feet straight out and up. Hold the dumbbells with bent arms right by your armpits then press arms straight up to the ceiling while bringing your feet straight up as well, then lower arms and legs back to starting position.