To grip the buttocks or not to grip the buttocks? That is the question. At least it's the question I hear most often when I teach backbends. Gripping the buttocks in backbends can lead to compression and pain in the lower back, yet you may feel you can barely get your hips off the ground if your buttocks aren't active. What's a student to do?
A better understanding of the movement of the hips in backbends—and of the muscles involved—may help solve the dilemma. In all backbends, you need full extension of your hips. Extension is the position of the hips when you are standing fully upright, and it is the opposite of hip flexion. The hips are flexed to 90 degrees when you sit and more deeply flexed when you pull your knees toward your chest. When you prepare to lift up into a supine (face-up) backbend like Setu Bandha Sarvangasana (Bridge Pose) or Urdhva Dhanurasana (Upward-Facing Bow Pose), you lie on your back with your hips partially flexed. As you lift your pelvis off the floor, you move into hip extension.
When you have even a little bit of bend at the hips, the tailbone drops down and the back waist lifts up. This position, called "an anterior tilt of the pelvis," creates a sharper bend in the lower back and often causes feelings of compression or pain.
There are two major causes of too much anterior tilt—in other words, lack of full hip extension—in backbends: tight hip flexors and weak or imbalanced hip extensors. If you have tight hip flexors, a very common condition in our sedentary society, it's important to stretch them before backbends by practicing lunges or Virabhadrasana I (Warrior I Pose).
But instead your problem may be partially or completely due to weak or unbalanced hip extensors. There are two primary hip extensor muscles: the gluteus maximus and the hamstrings. The gluteus maximus is the large, potentially powerful muscle that forms the shape of the buttock. It originates on the back of the pelvis and attaches to the outer upper femur (thighbone). The hamstrings, of course, lie on the back of the thigh. They originate on the ischial tuberosities (the sitting bones) and attach just below the knee on the tibia and fibula (the lower leg bones). Both muscles are potentially strong hip extensors, and your neuromuscular computer, otherwise known as your brain, may select one or both to lift your pelvis and open the front of your hips.
The answer to the question about gripping the buttocks lies in balancing these two muscles. If the gluteus maximus is doing too much of the work, you will begin to feel one of its secondary actions, external rotation of the hip and leg. To feel this for yourself, lie down on your stomach and put your left hand on your left buttock. Keeping your knee straight, lift your left leg off the floor (hip extension). Let your left leg externally rotate: Your knee and foot will point outward. The hand on your buttock should detect a strong contraction of the gluteus maximus. If you now try these actions of extension and external rotation with both legs at the same time, you will probably feel that you are "gripping the tailbone" with your buttocks.
The problem with this gripping action is that strong external rotation actually limits the ability of the pelvis to move into the posterior tilt desirable for backbends; it locks the pelvis in a position of anterior tilt and sets the stage for compression and discomfort in the lower back. To avoid this, it's ideal to create hip extension without external rotation, and the help of the hamstrings is essential.
The hamstrings are actually a group of three muscles. As a group, they help extend the hip and flex the knee. Individually, however, they perform different rotations: The biceps femoris on the outer back thigh helps with external rotation, while the semitendinosis and semimembranosis on the inner back thigh help with internal rotation.
To keep a balanced leg position in backbends, you need the gluteus maximus and the hamstrings working together to extend the hip, plus the inner hamstrings' action of internal rotation to cancel out the external rotation of the gluteus maximus. To feel this for yourself, lie again on your stomach with your left hand on the left buttock. Keep your left leg neutral, without external rotation, so that your kneecap points straight to the floor and your little toe is just as close to the floor as your big toe. Now lift your left leg off the floor, keeping your knee straight. With your hand you should feel that the gluteus maximus is firm, helping to lift the weight of the leg but not gripping the tailbone. If you press in with your fingers on the back of the upper thigh near your sitting bone, you should also be able to feel the contracting upper hamstring and its tendon. This is the optimal position for Salabhasana (Locust Pose), an excellent pose for training the hamstrings and gluteus maximus to work in a balanced way.
Why doesn't this balanced action come more naturally? Usually the most significant of many possible reasons are two problems that reinforce each other: tight external hip rotators and weak hamstrings. The external rotators include potentially very strong muscles: the gluteus maximus; the outer hamstring; the deep hip rotators (including the piriformis) underneath the gluteus maximus; and the iliopsoas, an external rotator in addition to its better-known role as a hip flexor. All of these can easily become chronically tight, especially if the opposing muscles (the two inner hamstrings and, in some positions, the adductors of the inner thigh) are not strong enough to hold the legs in neutral rotation. The second reason for the struggle with hip alignment in backbends—weak hamstrings—is actually fairly common among yoga practitioners. After all, a typical yoga routine contains hamstring stretches but often no hamstring strengthening.
Building Hamstring Strength
What poses should you use to help build hamstring strength and endurance? Ironically, the supine backbends, which can so easily cause lower back discomfort, are excellent hamstring strengtheners if practiced with proper hip alignment. To explore this, come into Setu Bandha Sarvangasana. As you lift your pelvis off the floor, the first clue about hip rotation is the balance of weight on your feet. If weight has shifted to the outer aspect of your feet, your legs are externally rotating. Directing weight into the inner heel and base of the big toe will put your hips and legs in a more neutral position—so will keeping your thighs parallel. If your feet and knees are turning out, your legs are externally rotating; knee pain in supine backbends is often due to overworking the external rotators, including the outer hamstring (biceps femoris). Holding a block between your knees in Bridge Pose can keep the thighs parallel, engaging the inner hamstrings and adductors to balance the action of the external rotators.
You can also more deeply engage the hamstrings in Bridge Pose with the help of a friend. Have her kneel at your feet and place her fingertips on the upper shin just below the kneecap. As you lift your pelvis, emphasize the lift of the tailbone so that you get a posterior tilt of the pelvis and full hip extension, avoiding lower back compression. Now pull your upper shins away from the helper's fingertips, fully engaging your hamstrings as well as giving more lift to your chest. Do not let the external rotators do all the work: Keep your thighs parallel and the weight balanced between the inner and outer aspects of each foot.
You can apply similar awareness to your feet, thighs, and shins in Urdhva Dhanurasana. Again the goal is to get a big lift of the pelvis and tailbone without externally rotating the legs and hips. Put a belt around your thighs, just tight enough to hold your thighs parallel. Lift into the pose and press your thighs out against the belt, using the gluteus maximus as an external rotator. You will notice that this action grips your tailbone and shifts your weight to the outer edges of the feet. Try the pose again: This time, after pressing out against the belt, keep the lift and lightness in your pose and pull your thighs in, away from the belt. While this action isn't easy for many of us, it does create a big, open backbend without lower back compression.
Now that I've provided you with all this anatomical information, you should be able to answer our original question: In backbends, the buttocks should be active and firm, but not gripping the tailbone.
A licensed physical therapist and certified Iyengar Yoga teacher, Julie Gudmestad runs a private physical therapy practice and yoga studio in Portland, Oregon. She regrets that she cannot respond to correspondence or calls requesting personal health advice.