We spoke with Dr. Stuart McGill, world-renown spinal expert and a professor of spine biomechanics at the University of Waterloo (Ontario), to find out if this exercise is as dangerous as it looks to the naked eye.
Unlike a traditional Sit-Up, it is performed on a glute-ham machine, which takes the floor out of the equation, so you are able to lower beyond parallel and hyperextend your spine, sometimes touching the ground with your hands before extending your knees and exploding up to complete the Sit-Up.
The spine is a series of joints made from collagen fibers arranged in rings. It can flex, extend and laterally flex to either side within a limited range of motion, but its inherent structure is designed for constrained movement and stability. The GHD Sit-Up does not treat it this way, taking the spine to the limits of its range of motion.
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