Many health practitioners recommend yoga as a means of combating stress—which, they point out, can compromise the neuroendocrine and immune systems. Stress by itself does not cause problems. In fact, the human body has a very efficient, built-in mechanism for dealing with stress.
What scientists call “fight or flight” response is triggered when we become frightened, anxious, agitated, or threatened. If you’ve ever stepped off the curb and just barely missed being hit by a bus, for example, you know what this syndrome feels like: As your adrenaline soars, your blood pressure increases, your heart pounds wildly, you sweat like crazy, your mind becomes hyperalert, blood rushes to your large muscle groups (in the arms and legs), and your breathing becomes shallow and rapid. To bring as much power as possible to your sympathetic nervous system (which controls this response) so the body can react quickly and efficiently, the body diverts energy from your digestive, reproductive, and immune systems, slowing them down to a bare maintenance level.
Once you realize that you’re out of danger, you begin to calm down and your system returns to normal. Unfortunately, those who constantly feel the threat of external stressors don’t give their systems a chance to return to normal. Their adrenal glands become exhausted from constantly pumping adrenaline into the system; the digestive and immune systems remain sluggish. A consistent yoga practice goes a long way toward mitigating the effects of the fight-or-flight response by giving your body the opportunity to rest completely.
But yoga does even more than that. Yoga can stimulate the bones to retain calcium, provided the body gets enough calcium in the first place. It does this through weight-bearing poses (like arm balances, inversions, and standing poses) that affect the whole spine, arms, shoulders, elbows, legs, knees, ankles, and feet, while encouraging full range of motion. B.K.S. Iyengar, master of yoga’s therapeutic applications, explains the benefits of yoga by means of what he calls its “squeezing and soaking” actions. He contends that through the process of squeezing out the old, stale blood or lymphatic fluids and soaking the area with fresh, oxygenated blood or fluids, yoga helps the body to utilize the nutrients it needs.
Inversions offer a perfect example of this phenomenon, particularly Sarvangasana (Shoulderstand) and Halasana (Plow Pose). These poses, according to Iyengar, regulate the thyroid and parathyroid glands (critical for metabolism) located in the neck, by creating a “chin lock” that squeezes stale blood from the area. As we come out of the pose and release the lock, the neck region is bathed in fresh, oxygenated blood. Iyengar also teaches that forward bends quiet the adrenals, and backbends energize them. Twists like Parivrtta Trikonasana (Revolved Triangle Pose), he says, are equally effective for regulating the adrenal glands, which we rely on to provide adequate amounts of estrogen and androgen for healthy bones.
A consistent yoga practice can give us confidence and stability as we move through the world. Many older people experience falls because they lose confidence in their ability to move properly; others suffer from poor eyesight, weakened muscles (often from lack of use), poor posture, or arthritis. Yoga can improve posture and coordination, strengthen muscles, increase flexibility, and create balance.