Why we don’t recommend Sit-ups
Summary: Sit-ups will wreck your back and a promote disc herniation.
Solution: To build core strength, focus on bridge and plank-based exercises.
When people say they do sit-ups regularly and are complaining of low back pain, stopping them is the first lifestyle modification we recommend. It has everything to do with the amount of pressure/stress you are applying to the lumbar discs.
Any position which loads a disc in an unbalanced way puts undue stress on the outer rim of the spinal disc called the annulus fibrosus (AF). Initially, the pressure causes a disc bulge. Then overtime, the AF breaks down and allows the jelly inside of the disc, called the nucleus pulposus (NP), to leak out. This is called a herniation (See Figure 1).
This structural breakdown will typically start out as an “achy” low back pain associated with sitting or activity. If not corrected, some vague unilateral (one sided) pain may begin to develop. As the outer layers of the disc gradually break down, the disc begins to herniate. The process can be abrupt or measured. The presence of a herniation leads to a “pinched nerve,” which is a term we have all heard of? When a nerve is “pinched” the herniated NP is actually compressing the nerve root as it extends into the spine. In the lower spine it causes weakness and pain down the leg, and can sometimes lead to surgery.
So where do sit-ups come in? And why are they bad? The act of flexing at the waist loads the spinal discs as described above. Flexing and contracting actually loads the lumbar discs even more. In Figure 2 below you can see that the act of sitting increases the pressure in your lower back over two times compared to standing. You can also see that lying down reduces the pressure significantly.
So what will you do without your precious sit-ups? How else will you achieve washboard abs unaccompanied by this workout regimen cornerstone?
Even without the negative effects to your back, the sit-up really isn’t a good core exercise. The sit-up exercise is only working one muscle group called your rectus abdominis(the 6-pack muscle), and some experts don’t even consider it part of you “core” core muscles. If the rectus abdominis becomes more dominant than the other muscles in your core such as the diaphragm, pelvic floor and multifidi seen in Figure 3, your core actually becomes weaker and more unstable, because of the muscular imbalances.
The best way to stabilize your core is to do so while your lower spine is in a relatively neutral position. We start patients out with a series of exercises which builds upon an action called the “abdominal brace.” From there, our patients build up to plank and bridge-based exercises. While these exercises are not free from load, they do apply pressure more evenly to the disc. In this manner the disc is better able to distribute the applied pressure and is therefore more resistant to injury and degeneration. To see videos on how to build your core from the ground up without hurting your back click here.
Figure 2: Lumbar Disc Pressures, Adapted from https://musculoskeletalkey.com/the-lumbar-spine-3/#bib92