Positioning the Heels in Backbend
—Bianca Wiedemann, GermanyRoger Cole's reply:
Squeezing the buttocks and keeping the heels together makes backbends harder, not easier, on the lower back. Here's why: An essential part of backbending is extension of the hip joints (the position in which the top rim of the pelvis is tilted backward relative to the thighs and the sit bones are forward). If the pelvis doesn't tilt back, you force your lower back to do too much of the backbending action, and it hurts.
Squeezing the buttocks and joining the heels engages muscles that outwardly rotate and separate (or abduct) the thighs. Some of these muscles prevent the pelvis from tilting fully back into the backbending position. In addition, rotating the thighs out and separating them brings the top, outer part of the thigh bones (the greater trochanters) behind the pelvis, where they also block a backbending movement. If the pelvis doesn't do its share of the backbend, the lower back takes too much of the bend.
A part of the buttocks (the lower part of the gluteus maximus) should contract in backbends, however. Its job is to help extend the hip joint while avoiding external rotation. To learn to distinguish helpful from unhelpful actions, try this exercise. Stand upright in Tadasana (Mountain Pose). Put all your weight on one foot. Without leaning the torso forward, lift the other leg straight behind you, keeping the knee straight.
Turn your head and look back at your lifted foot. Notice that the toes are turned part way out, the heel in. This is because the gluteus maximus muscle that lifts the leg extends the hip joint and externally rotates it. So at this point, you are contracting both muscle fibers that are helpful for backbends (those that extend) and muscle fibers that are unhelpful (those that externally rotate).
Feel the buttock of the lifted leg with one hand. Notice that most of it is contracted. Now, keeping the leg lifted, squeeze your two buttocks together. Notice that the upper part of the buttock contracts more, and the lifted foot turns out more. Now you are contracting still more unhelpful muscles that cause external rotation.
Return to standing upright on two feet in Tadasana. Turn both feet in, with big toes touching and heels separated about 6 inches (15 cm). Again lift one foot straight back as before, but this time, strictly maintain the internal rotation of the thigh, so the toes still point in and the heel stays out. Now feel with your hand which part of the buttock is contracting.
You will find that the lower buttock where it joins the thigh is firm, but the upper buttock (the place that contracted when you squeezed the buttocks together before) is now soft. This is the correct action for backbending, because it selectively contracts those muscle fibers that extend the hip joint while avoiding those fibers that externally rotate it.
Note that people who backbend very easily at the hip joint may be able to do some backbends without contracting any part of the gluteus maximus at all, even the part that extends the hip joint. However, everyone must contract those gluteus fibers at least somewhat in poses like Setu Bandha Sarvangasana (Bridge Pose), Urdhva Dhanurasana (Upward Bow Pose), and other postures that require lifting the pelvis off the floor from a supine position.
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 pPranayama. He teaches workshops worldwide. For more information, visit http://rogercoleyoga.com.