According to the studies on spinal disc pressure by Dr. Nachemson, there is 210% of your body weight of pressure into the spinal disc with sit ups, and 180% of your body weight of pressure with back extension.
For example: If your weight is 150 pounds and you do a sit-up, you are putting 330 pounds of pressure on your spinal discs per repetition, in other words, this is a very effective exercise to rupture a disc.
