Lie down on your back on the ground. Your legs should be straight and your arms extended over your head holding a watermelon. Lift your arms and legs a few inches of the ground.
Bring the knees toward your chest, rotating your pelvis to lift your glutes from the ground. As you do so, flex the spine, bringing your arms back over your head to perform a crunch motion. The watermelon should be over your lower legs. Pause for a second.
Return to the starting position and repeat the exercise according to the training plan.