Initially, about dorsal raises, they said:
The exercise has other names but this is the most common. It is performed by laying flat on your stomach and raising the upper body and legs off the floor. In this exercise the lumbar spine pays a very high compression penalty to a hyperextended spine (approximately 4000 to 6000 N) which transfers load to the facet joints and crushes the interspinous ligament. This exercise is certainly contraindicated for anyone at risk of low back injury or re-injury due to the high spine loads and the extended posture. In my opinion it should not be prescribed at all.
Then about dreaded sit-ups:
Also it brings up the question of whether anyone should perform the sit up. Next sit up is the “press the heels” made famous by Czech neurologist Vladimir Janda. The exercise is performed like a typical bent knee sit up except the feet are dorsiflexed and the heels are then pressed into the floor. It has been hypothesized that by pressing the heels into the floor and activating the hamstrings this would neurally inhibit the psoas. Thus there would be increased load on rectus abdominis and decreased low back loading.
Actually EMG data showed that by pressing the heels into the floor the psoas activation actually increased! Athletes who are intentionally trying to train psoas will find this information informative. Those with low back injury or risk of re-injury would be wise to avoid the “press the heels” sit up.
The numbers here come from the great books by the genius Prof Stuart McGill. He has a profound grasp of what’s happening in the low-back during these sorts of exercises and is very cautious about the benefits of the sit-up.
My advice is just don’t do them as there are far, far better things to be doing with your time.