You can often tell who's new to yoga and who's not by looking at their backs and trunks in Paschimottanasana (Seated Forward Bend). Newbies tend to round the spine deeply and collapse the front of the body, while those who have been around the yoga block a few times are more likely to completely flatten the spine and fully open the front of the body. You may be surprised to learn that neither position is optimal.
Early on in your yoga practice, someone probably told you that it's dangerous to round your back. This is true: If you round too far, you can rupture a spinal disk, tear a ligament, or strain a muscle. Keeping your spine straight as you bend forward can help you avoid those risks, and it has other positive effects, too, such as strengthening the back muscles and freeing the breath in the front of the body. This is why many teachers advise you to create a "forward fold" from the hip joints rather than a forward bend from the spine.
The problem is, taking this advice to an extreme and holding your spine completely straight as you bend forward can cause trouble of its own. For starters, it makes you more likely to tear a hamstring tendon or strain the sacroiliac joint. Not only that, but by keeping your spine superflat in a forward bend, you miss out on some of the best structural and psychological benefits of the pose: namely, developing suppleness in your spine, easing tension in your back and neck muscles, and cultivating a contemplative, inwardly focused state of mind. To experience the richness of for ward bends you have to—guess what?—actually bend your spine forward. The trick is to learn to bend it just the right amount.
Joy of the Flex
Moderately rounding your back on a regular basis is not only good for your spine, it's also essential to its health. In order to stay flexible and functioning at its peak, the spine needs to move in every direction on a regular basis, through flexion (rounding forward), extension (arching backward), rotation (twisting), and sidebending. These movements nourish and mobilize the spinal disks, ligaments, muscles, and tendons by squeezing fluids into and out of them, gently stimulating the cells within or around them, and preventing adhesions (spots where tissues stick together). The benefits of judicious rounding are more than just physical.
The muscles of your back and neck hold your trunk and head upright when you interact with the world around you, and some of the same parts of your brain that make your mind alert and active also tense these muscles. Stretching and releasing the muscles allows you to quiet those activating parts of your brain, promoting a state of rest and calm. You can enhance this effect by bowing your head slightly, which turns your gaze away from the distractions of the outside world and directs your attention to the universe inside.
To reap the rewards of rounding, you have to find the middle way between too much and too little spinal flexion. Rounding too much is by far the more dangerous of the two, especially in seated, straight-legged forward bends. To understand why, imagine a woman with tight hamstrings struggling to perform Paschimottanasana. She's sitting on the floor with her legs straight out in front of her, pelvis rocked backward, hands gripping her feet, pulling hard with her arms to sharply curve her trunk forward and down in a futile effort to bring her head to her knees.
The tightness in her hamstrings prevents her pelvis from tilting forward at the hip joints, so as she pulls, her spinal vertebrae tilt forward. This pinches the fronts of the vertebrae together and opens up the spaces between them in back, which overstretches the ligaments, muscles, and the rear walls of the disks that hold the back of her spine together. It also squeezes the front part of the disks that lie between the vertebrae, which can force the jellylike nucleus in the center of a disk to push backward against a weakened rear wall. This pressure can make the wall bulge or rupture. Either a bulge or a rupture can push on a nearby nerve, causing, for example, sciatica.
A rupture lets some of the "jelly" escape from the disk; this is a herniated disk (commonly but inaccurately called a "slipped" disk). This imaginary Paschimottanasana illustrates a very real and sobering fact: If you force your back to round in a forward bend, particularly a seated, straight-legged one, the strain goes directly to your spine. In mild cases, the strain simply weakens the ligaments and muscles there, making your spine less stable and strong. In more extreme cases, it can rupture a disk or tear a ligament or muscle. Such injuries can put you out of commission
Although being too straight is not nearly as risky as being too rounded, it's still not ideal. If you bend forward only from your hip joints in Paschimottanasana, and stop trying to move deeper into the pose the moment your hamstrings pull taut, keeping your back completely flat probably won't hurt you, but you won't get nearly as much mental or physical relief as you would have gotten if you had gently rounded your back. If you insist on pulling your trunk ever closer to your thighs while holding your spine rigidly straight, the movement has to come from somewhere, and that can spell trouble. Either you will end up tilting your pelvis further forward, which will focus the force of the pose on your hamstrings, potentially leading to a tear in one of the tendons that connect the hamstrings to the sitting bones. Or you will tilt your sacrum forward relative to your pelvis, which can destabilize your sacroiliac joints.
When in Yoga...
Happily, it's not difficult to find a safe and rewarding path between too little and too much rounding of your back in forward bends. To visualize it, imagine what the best forward benders in the world look like. You've seen their pictures in yoga magazines like this one, folding neatly into Paschimottanasana, hamstrings so loose that their hips flex forward without a hint of resistance, the entire length of their front body resting, long and comfortable, on their thighs. But look again and you'll see that even these uber-benders round their backs in the pose. In fact, it's anatomically impossible to keep the back perfectly straight when you go all the way down, chest to thigh, in Paschimottanasana; the pelvis simply cannot tilt forward
If a superflexible person moves into the pose by tilting forward only from the pelvis, keeping the back straight, the pelvis will hit the thighs and stop tilting before the chest reaches the thighs. The only way to get the chest down the rest of the way is to round the back, and the amount of rounding will be limited because the breastbone and rib cage soon press firmly against the thigh muscles.
This natural stopping point creates a comfortable curve of the trunk that avoids extremes of flexion or flattening. Thus, to round your own back by a reasonable amount in a forward bend, all you need to do is create the same long, even curve in your trunk. But before you get your hamstrings in a knot just imagining bending as far forward as a "yoga supermodel" does, take heart: You can easily create the identical amount of spinal curve even if your pelvis barely tilts forward at all. You do this by tilting your pelvis forward until it naturally stops, then creating a gentle, smooth arc of your trunk, neck, and head by systematically tilting each vertebra forward a little bit.
Here's how: Sit with your legs straight out in front of you in Dandasana (Staff Pose). Using folded blankets, or even a chair, elevate your pelvis high enough that you can easily tilt the top of your sacral area forward of your tailbone. Then, keeping your legs completely straight, inhale as you push your hands down into the floor, blanket, or chair seat alongside your hips, lift your chest high, and draw your lower back slightly forward into your body. As you exhale, push your hands down and backward to elongate your spine as you slowly bend forward from your hip joints. Move your pelvis, spine, and head forward as a unit, keeping your head in line with your body, as in Tadasana (Mountain Pose).
The moment the hamstring stretch stops your pelvis from tilting further forward, stop your spine too. Now it's time to begin systematically rounding your back.
Keeping your pelvis where it is, deliberately round your spine forward from the junction between your lowest lumbar vertebra (L5) and the top of your sacrum (S1). Continue moderately bending your spine forward, one vertebra at a time, from the bottom to the top. Make sure that each segment contributes evenly to the bend, and that none overworks. You should feel absolutely no strain anywhere in your back.
If your torso moves so far forward that your hands can no longer effectively push down and back alongside your hips, then bring your hands to your shins or feet and use them to support and control your descent into the pose; otherwise, leave your hands by your hips. When you have worked your way up your spine to your neck, tilt your chin down a little so your head bends forward moderately. Do not drop your chin too far or hang your head.
If someone were to look at you from the side, they would be able to trace a smooth, even curve from the side of your hip joint upward, along the sides of your waist and rib cage, through your shoulder joints, along the sides of your neck, and through the openings of your ears. Although your pelvis and ribs may be nowhere near your thighs, the curve of your trunk should be identical to the one you would see on a well-aligned person doing a belly-and-chest-on-thighs forward bend.
If, after holding this position for a few breaths, you feel you can release your hamstrings a little more without forcing them, then exhale as you tilt the top of your pelvis forward a bit more. This will partly flatten your lower back. Now, keeping your pelvis stationary, restore the same forward-flexing curve you had in your back a moment ago by rounding systematically from L5 to S1, then from L5 to L4, and on up the spine.
Once you're at your reasonable maximum, stop, move your eyes slightly toward your lower lids, look inward, and enjoy the asana. Now you not only have the spinal curve of an uber-forward bender, you have the mind of one, too.
Roger Cole, Ph.D., is a certified Iyengar Yoga teacher and a research scientist specializing in the physiology of relaxation, sleep, and biological rhythms. He trains yoga teachers and students in the anatomy, physiology, and practice of asana and pranayama. He teaches workshops worldwide. For more information, visit http://rogercoleyoga.com.