I am constantly asked by patients if they should be doing crunches to strengthen their core and reduce their back pain. The answer is an emphatic NO.
The reason is best explained by our anatomy. There are four layers of abdominals, all spanning the entirety of the abdomen from the front pubic bone to the rib cage. The rectus abdominis is the most superficial muscle group, and their function is to flex the trunk forward- as if to bend forward, or perform a crunch. The next two layers are the external and internal obliques. These rotate and side bend the trunk, and due to their insertion into the thoracolumbar fascia (tissue attatching the the spine itself), it is credited with assisting in spine stabilization, and is a member of the infamous “core”. The deepest layer of abdominals is the transversus abdominis- or the transverse abdominals. These muscle fibers transverse the spine just as a belt would, and when contracted directly stabilize the spine. They are considered an extremely important muscle group in spine health, and of course are part of the “core”.
Pictures of these structures can be seen at the human kinetics website below:
Crunches, done with feet either planted on the ground with knees bent, or hovering in the air only exercise the most superficial abdominal muscles-the rectus abdominis. They do not activate or utilize the other three layers at all. Also, interestingly, though the goal of these exercises is usually to flatten the stomach, performing repetitive crunches will actually lead to bulking of the rectus abdominis, leading to a thicker, pouchy-like abdominal appearance. Furthermore, the repetitive flexing forward can cause irritation of the spine, both at the neck and the lower back, leading to pain.
So, how do you strengthen the core in an efficient and safe way? Beginning each exercise by drawing the abdominals into your spine will activate the deepest layer of abdominals- the transverse abdominis. From there the exercise should continue to challenge these muscles. Here are some classic exercise to strengthen the core muscles and protect the spine:
Starting on your hands and knees, press legs out straight behind you, maintaining your head, hips, and knees in a straight line. Hold 30 seconds. If a full plank is too difficult for now, you can drop down onto your elbows and knees.
Start with knees hovering in the air bent at a 90 degree angle, with your back in a neutral position (not smashed into the mat or arching up away from the mat) and your belly button pulled in. Rotate your trunk bringing your Right elbow to your Left knee. Exhale and switch, bringing your Left elbow to your Right knee. Repeat 10 times on each side.
Half Roll Back
Begin sitting up tall with your knees bent and feet shoulder width apart. Engage your abdominals by pulling belly button into your spine, and reach your tailbone down towards the floor, rolling your pelvis back, and hollowing out your stomach. Keep your eyes on your knees, maitain the hollowed stomach, and bring yourself back up to seated position. Repeat 10x. This is different than a crunch due to the order of activation of the muscles, and the deliberate contraction of the transversus abdominis.
Either propped on your elbow, or all the way up on your hand with fingers facing forward, keep your bellybutton in and hold 30 seconds. Repeat 3x on each side.
Make your day great,