How To Keep Your Ab Crunches Safe

Abs and core. Abs and core. Abs and core. Sometimes it seems like that’s all we hear about in fitness. Some of us would love to get rid of the fluff around our middle by doing a bunch of ab crunches. Others are aware that a good, solid group of core muscles is essential for most of our movements. In addition, a good core is supposed to protect your low back from injury.

But, there is another consideration here. Sometimes, you can actually put undo stress and strain on your low back by doing abdominal exercises. Is there some sort of fine line where doing too many can hurt you? Or is it something else?

Your Psoas Muscle

Here’s the something else. It’s called your psoas muscle. While not actually part of your abdominal group, it often plays a part when you are crunching. Why?

Your psoas muscle is a big one that starts by joining up with all of your lumbar vertebrae (that’s what makes up the spine segments of your low back). It ends up attaching to the top of your thigh bone. When this muscle contracts, it brings your leg closer to your torso. Or, if your torso moves toward your leg, it will also contract. In other words, it is the muscle that flexes your hip, your hip flexor. Now, in case you hadn’t noticed, many of the exercises we do for our abdominals involve bending our legs at the hip.

Why would that ever be a problem?

Turns out that whenever you bend at the hip, the psoas gets activated. That’s just fine UNLESS for some reason the contraction of that muscle ends up pulling on your low back. If that happens over and over, it can be a recipe for disaster for you and your back. This is just what happens in many common abdominal exercises.

Let’s take a look at three different ab exercises to discover the difference in terms of the health for your low back.

1. The ab curl.
This is where you lay on you back, knees bent, hands behind your head (see below). Once in that position, you curl forward, using your abs to get the curl. You only go as far as to get your shoulder blades mostly off the floor. Then you go back, slowly uncurling, to get to the starting position.

This exercise is just fine for you and your low back. That’s because, even though the hip is bent (flexed), as you curl forward, you do not ask your hip flexor to bend even more to get you to come up further. So there is no additional pulling or strain. The psoas stays mildly contracted but nothing else, and your abdominals are given a chance to work.

2. The classic “sit up.”
Here you start out in the same position as the ab curl (see below). However, you keep going on up, past the place where your shoulder blades come off the floor, and end sitting all the way up. If you have ever done these, you may have felt a pull on your low back as you come up. The deal is that once you get past just getting your shoulder blades off the floor, your psoas has to contract even more to help you get up. Your abdominal muscles actually stop working as a major player, and your psoas is doing much more of the work. So, not only are you not working your abs at this point, but the exercise can produce strain on your back. Something that may catch up with you eventually as an unwanted injury.

3. Straight leg lifts.
This exercise is where you take both legs, keep them straight, and lift them up and down off the ground. (see below) There are a bunch of variations of this, but this is the basic one. The trouble here is that as you lay there, your low back has its normal curve. That’s OK, but when you lift your legs off the floor, your hip flexors are working very hard to get this move done for you. Your psoas is contracting like crazy. And, since your low back is in a curve already, the psoas pulls on that curved part, puts an enormous strain there, and can even force your vertebrae out of alignment. Ouch!

THE BASIC LESSON: Your abdominal muscles are there to help you curl your torso, scrunch it together, bringing your head toward your naval. That’s it. They are not there very much as you go from laying down to sitting up or as you lift your legs off the ground. Those activities will call your psoas into play. You may feel your abs working in those exercises, but that’s because they are bracing and stabilizing against the powerful psoas.

P.S. There are plenty of exercises for your abdominals that may be mixtures of the exercises presented. In general, using your abs to help you curl your torso with variations will keep you in the low risk zone. Meanwhile, do your best to stay away from exercises like #2 and #3.

All the best
Kristen