The Sit Up is a great beginner movement for those looking to strengthen and tone their abs. The main difference between a Sit Up and the Crunch is that the Sit Up has you bringing your upper body much further up off the floor.
However, care must be taken to perform the Sit Up correctly, as incorrect form can place undue stress on your head and neck. This is a floor-based movement, so make sure to use a comfortable mat for your back.
Start by lying with your back and your knees bent so your feet are flat on the ground beneath you around hip-width apart.
Place your two hands gently behind your head with your elbows flared out to either side. Your neck and head should not be pushed or pulled up by your hands. Your hands will be guiding your head and neck throughout the movement, but not using force to lift them.
Contract your abdominal region, exhale, and start to raise your upper body while keeping your feet and buttocks firmly on the ground.
Lift your torso up off the floor until your chest is almost completely upright, then inhale and slowly lower yourself back down. This counts as one Sit Up. It’s fine if you find that your feet shift somewhat in front of you.
Try to keep your back, neck, and head lifting up in unison and with straight continuous posture throughout the movement.
Do as many reps as you can until failure.