calisthenics / compound
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Get yourself into a laying position with your hands over your head while holding onto your workout bench or something stable (chair, low table, etc).
Keep your hips straightened and your knees taught, utilize your abdomanal region to lift yourself upward into the air.
At this point you should keep your body weight pushing directly on your shoulders and your body altogether straight. Continue to raise your legs until your body is upright to the bench.
Continue to lower your body downward while making sure to keep your body is straight until your back is flat on to the bench (chair, low table, etc).