Instructions
Kneel on the floor grasping a loaded barbell. Position the barbell near your knees and lean over it with arms extended downward, supporting your upper body. Keeping your arms straight and core braced, roll the barbell out as far as possible while you lower your body down to the floor. Raise your body back up by flexing your hips and pulling your arms back until your body is in its original position. Repeat.
Tips
To decrease the intensity of this exercise do not roll the bar out as far. Use a wall to stop you from going further than you can control. You can see a demonstration of this in this video.