Forward and backward bending postures, as well as flexion and extensi< i in general, always take place in relation to earth's gravitational field. I t twisting is fundamentally different because you can twist the body or soi e part of the body without altering its relationship to gravity. For examp , you can twist your head as far as possible right and left, but unless u combine this with flexion, extension, or lateral flexion, the relationshij of the head to earth's gravity is unchanged.
Bends and twists not only differ in nature, they differ in how they cc le about. Any movement that involves bending -whether whole-body bend ig, or flexion and extension of a limb—gets its impetus either from interact j us with gravity or from a force like that created when children in swing 'ts kick their feet forward and then backward to get themselves going, or ke that created when you push off from the end of a swimming pool. All he twisting motions with which we are concerned here, however, are initi ed by torque. It is torque that starts someone spinning around on a rota ng chair, and it is torque that the rotators of the hip use for rotating the ng axis of the thigh with respect to the pelvis.
(Technical note: To be accurate, it has to be admitted that nearly all movemei at joints use torque, whether bending your elbow, kicking a football, or grasj ti a pencil. That is why I was careful not to say that linear movements are use for pushing off from the end of a swimming pool. That would have been incoi -ct; torque is used there as well to extend the hips, knees, and ankles. The diffi ice is that for those movements the axial center of rotation is in each specific nt, whereas in this chapter our main concern is with forces that operate to create 'is* on the long axis of the body or limb from the perimeter of an imaginary circli liat surrounds the axis of the affected body part.l
Bending and twisting differ in at least three more ways. First, for ird and backward bending are often symmetrical, but twisting can neve be: it always pulls structures on the right and left sides of the body in opp 't® directions. Second, forward and backward bending need not increase dal tension in the body, but twisting, unless it is utterly unresisted, ah »>'s compresses structures that lie in the axis of the twist. Last, while fon ird
and backward bending are comparatively simple expressions of flexion and extension, there are several different kinds of twists: rotations of synovial joints, more constrained spinal rotations, and whole-body swivels that combine both of the above.
Simplistically, and for purely practical purposes, we can state that torque is any mechanical force that can produce a rotation. It is initiated by muscular effort, but like any other force, that effort does not have to produce a visible result. It is like a push. You can push against a sapling and bend it, or you can push against a tree trunk to no avail. And so it is that a torque can either actuate a twist or it can be an isometric effort that attempts a twist but fails—trying to twist a locked doorknob, trying unsuccessfully to escape having both shoulders pinned to the floor in a wrestling match, or tugging on the rope of a frozen lawnmower engine. In hatha yoga the muscular effort to come into a spinal twist creates torque throughout the body, actuated in some regions, in others not.
synovial rotations in the extremities
The simplest kind of twisting involves free and easy rotation at synovial joints, in which the slippery cartilaginous mating surfaces of bones offer little or no resistance to movement. We see this when we "twist" a screw into a board, alternately pronating and supinating the forearm. As shown earlier (figs. 2.8 and 4.3), these rotations take place because two pivot joints, the proximal radio-ulnar joint at the elbow and the distal radioulnar joint at the wrist, permit the ulna and radius to come into an X configuration for pronation and into a parallel configuration for supination. Other familiar examples of synovial rotations are the rotary movements of the femur in the ball-and-socket hip joint and the rotary movements of the humerus in the glenoid cavity of the shoulder joint (fig 1.13).
The second kind of rotation, and the one that the hatha yogi first thinks of as a twist, is rotation of the spine. Whether standing, sitting, supine, or mverted, spinal twists involve the entire torso, but they all start with axial rotations between adjacent vertebrae. Taken together, such rotations—24 °t them in all between Ci and the sacrum—add up to a lot of movement, even though this takes place against the resistance of intervertebral disks, facet joints between the vertebral arches, the rib cage, and muscles and ligaments from the head to the pelvis. We rarely do complete spinal twists in everyday 'ife, but they are one of the five fundamental gestures in hatha yoga.
jK6 ANATOMt OF HATHA YOGA
Another kind of twist might better be called a swivel. It involves rotatii ^ the pelvis and thighs around so that the torso faces to one side, and t invariably begins in a standing position with the thighs at least partial y abducted. The swivel can be limited to the lower extremities, but mo e commonly it is a whole-body twist in which the hips, shoulders, and toi o are all rotated in the same direction, usually at the same time. Swivel in), is a combination of spinal and synovial twisting—a spinal twist superimpo!- d on synovial rotation of the hip joints. In sports we often see these mo e-ments taken to their extremes, as when skiers negotiate a steep drop w h short, side-to-side excursions while keeping their shoulders perpendici ir to the fall line of the downhill slope. And in everyday life, any time m face the torso in a direction other than straight ahead but do not shift >ie feet, you swivel at the hips. In hatha yoga practically any stanc lg posture that involves planting the feet and then turning the rest of he body is a swivel—a spinal twist combined with medial rotation of ne thigh and lateral rotation of the other.
For practical purposes, how a posture feels to us is our major conc -n, so from this point on, if it feels like a twist we'll call it a twist, wheth it is a free and easy synovial rotation, a constrained spinal rotation, a s\\ el, a torque that goes nowhere, or a torque that produces a movement e\ ry-one recognizes as some kind—any kind—of a twist.
stability in twisting
Tiy to imagine how difficult it would be architecturally to design a mt that is stable enough to twist as well as permit flexion and extension You would probably limit flexion by allowing the joint to fold in on 1
completely, but you would need to include both ligaments and bony >ps to limit extension. That's easy enough. But to permit that same joi to twist as well, you would have to include a complex of muscles to act ate the twisting, and you would have to superimpose any number of sped; /.ed ligaments and muscles on the joint to keep the twisting within reaso ble bounds.
This is not a small order, and as a general rule, wherever extensive fl ion and extension take place, we see that twisting is limited. In the lu bar region of the spine, which is the site of most spinal forward and back ard bending, little twisting is permitted, but in the chest, where backber ing and forward bending are limited, we see excellent potential for twi ng-
And in the extremities, the fingers and toes permit flexion and extei ion but little twisting. Only in the cervical region of the spine, in the hip: md shoulders, and in the flexed knees will we see extensive flexion and extei i°n as well as the additional potential for rotation, and those regions are as si ible
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as they are only because of robust, muscular support and numerous restraining ligaments. Even so they are all hot spots for dislocations and other injuries.
asymmetry and twisting
Whole-body twisting is always accomplished by pairs of obliquely oriented muscles, one on the right side of the body and one on the left. The muscle on one side shortens concentrically, creating the twist, while the muscle on the other side lengthens, resisting the twist. The external and internal abdominal oblique muscles in the abdominal wall are a case in point. As you twist to the right, the right external and the left internal abdominal obliques shorten concentrically, and the right internal and left external abdominal obliques lengthen against resistance. On the other hand, vertical muscles such as the right and left rectus abdominis, as well as horizontal muscles such as portions of the right and left transvcrsus abdominis, remain the same length during a twist and simply come under isometric tension equally on both sides.
All ligaments that run obliquely on the two sides of the body are also brought under asymmetrical tensions by twisting. If you bend your knees and twist the torso to the right, as you do when you ski to the left while your shoulders are facing downhill, excessive lateral rotation of the left leg will be checked by the collateral ligaments of the left knee, and excessive medial rotation of the right leg will be checked by the cruciate ligaments of the right knee. Skiing to the right, of course, mirrors these tensions. By contrast, if you stand in a symmetrical knock-kneed position with the toes facing in and heels out, the ligaments are stressed symmetrically rather than asymmetrically Excessive medial rotation of both legs is checked equally by the cruciate ligaments on both sides. Or if you stand with the feet wide apart, heels in and toes out, excessive lateral rotation of both legs is checked equally by the collateral ligaments of both sides.
Ordinary activities such as walking keeps the two sides balanced, but when you twist you usually favor one side—always holding a book to one side and twisting the neck in the same direction, or always coming up on the same side for air when you are swimming freestyle. Or if you consistently hold the top of the handle of a snow shovel with the right hand and throw the snow to the left, you will develop more strength, stamina, and flexibility for twisting to the left.
Twisting habitually to the same side during the course of daily activities distorts the body's bilateral symmetry, and such biases sooner or later Produce asymmetries in its structure. For this reason twisting postures should always be done in both directions, and to correct imbalances they should be done three times—twice on the less flexible side.
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