Make sure your yoga practice is helping, not hurting, your back
A yoga practice with too much emphasis on aggressive forward bending can be risky, particularly if the student has tight hamstrings and a flattened curve in the lower back. A well-constructed yoga routine, however, can be an ideal way to learn to stretch without creating or exacerbating back pain, and a chance to practice good alignment and movement patterns which help protect the back from injury.
To understand how stretching can improve or aggravate disc problems, let’s look at how a disc works and how it gets damaged. Intervertebral discs function as shock absorbers, cushioning the brain from jarring as we walk, run, and jump. Each disc consists of two parts: the inner disc, the nucleus pulposus, made of a shock-absorbing gel-like substance, and the annulus fibrosis, the rings of ligament that surround and support the center.
A normal lumbar spine has a mild curve forward, and in this position, weight is evenly distributed throughout each disc. During toe-touching, the lower back flexes, losing its normal curve, and more weight is put on the front of the discs. The gel-like centers get pushed backward, into the now stretching support ligaments. While this can happen during forward bending even if a person tends to have excessive lumbar curve (“swayback”), it is especially problematic if the spine has lost the normal curve and become flattened.
With repetition, or if great force is applied as in heavy lifting, the ligaments weaken and may “bulge” like a bubble in the wall of a tire. Or the ligaments may tear, allowing the gel-like inner disc to leak out, resulting in a herniated disc. The bulging or herniated disc may cause lower back pain or, if it is pressing on an adjacent nerve, pain can be referred into the hip and leg. Bulging and herniated discs may be treated conservatively, with physical therapy, exercise, and other noninvasive treatments, but a badly herniated disc is a serious medical problem which may require surgery and a lengthy recovery period.
While heavy lifting is a well-known cause of back injuries, disc damage is just as frequently caused by the smaller but repetitious forward-bending movements we make during daily activities at work and at home. For most of us, half of our body weight is above the waist. Just as a child “weighs more” as he or she slides away from the center to sit at the end of a teeter-totter, our own upper body weight exerts greater force at the disc as we bend farther forward. This tremendous force on the disc, added to the strain on the supporting ligaments, sets the stage for damage.
In our society, opportunities abound for repetitive forward bending: child care, yard work, housework, shopping. Even sedentary work may exert strain on the lower back; for example, someone bending and twisting from a sitting position to lift a heavy object out of a bottom desk drawer. The greater the weight being lifted (and the weight of one’s own body), the greater the pressure on the disc.
Forward bending activities, especially combined with lifting, are also the most common cause of back “strain.” While much less serious than disc injuries, back strain is responsible for most of our lower back pain, including the Monday morning ache after weekend gardening.
Repetitive forward bending may also occur in exercise routines, including yoga. These routines can be particularly risky for people with tight hamstrings, the muscles extending from hip to knee on the back of the thigh that receive much of the stretch in forward bends. The hamstrings attach to the sitting bones—the two large bones at the base of the buttocks (called the ischial tuberosities). In a sitting forward bend, the pull of tight hamstrings keeps the pelvis from rotating forward over the legs. In fact, tight hamstrings encourage the pelvis to rotate backward, in a position called “posterior tilt.” If your pelvis is held in a posterior tilt and you reach toward your toes, all the forward movement occurs by hinging through the lower back.
Doing a series of sitting forward bends, then, can put prolonged or repetitive strain on the disc, causing or contributing to disc bulging or herniation. Ironically, the people who most need to stretch their hamstrings, to help improve posture and movement patterns, are most at risk for injuring their backs practicing forward bends.
Tight hamstrings affect posture and the health of the lower back by exerting a constant pull on the sitting bones, tipping the pelvis posteriorly and flattening the normal curve of the lumbar spine. Overly strong or tight abdominal muscles may also contribute to a habitually flattened lower back. Tight abdominal muscles pull up on the pubic bones, again contributing to posterior tilt, especially if combined with tight hamstrings. They also pull down on the front rib cage, contributing to forward-slumped posture. This posture, with posterior-tipped pelvis and forward-slumped trunk, puts chronic strain not only on the discs, but also on the lower back muscles.
Many who suffer from lower back pain have heard or read that strong abdominals are the key to pain relief. It is true that the abdominals are important support muscles for the lower back, especially for problems like arthritis and swayback.
Problems arise, however, when the abdominals are strengthened with regular exercises like sit-ups or crunches, but the back extensors—the long muscles running parallel to the spine that support it and maintain and increase the normal lower back curve—are ignored.
Over time, a muscle imbalance develops: The abdominals become stronger and tighter, while the back becomes relatively weaker and overstretched. Unfortunately, many current exercise routines emphasize several types of abdominal strengthening, and a series of sitting forward bends to stretch the legs. The end result of years of this type of exercise will be a rounded, slumped posture with a weak and vulnerable lower back.
When faced with challenging poses, students are likely to fall back on familiar positions and muscle patterns. If your usual posture is rounded forward, with a flattened lower back, posterior-tilted pelvis, and tight hamstrings, you are at risk for back injury in forward bends and need to take special care as you prepare to practice them. Your goal is to be able to stretch the hamstrings without a posterior tilt of the pelvis.
Evon Stone Rubenstein, YTRx500, RYT500