Increasingly, research shows that practicing yoga quiets the stress response system by regulating the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic nervous system (SNS). (Read more on how stress works.)
Studies reveal that yoga practice:
- decreases levels of salivary cortisol, blood glucose levels, plasma rennin levels and 24-hour urine epinephrine and norepinephrine levels
- regulates the heart rate and significantly decreases systolic and diastolic blood pressure
- increases immune system function and decreases markers of inflammation
In addition to these physiological effects, yoga has also been shown to decrease anxiety, relieve symptoms of depression, and increase feelings of emotional, social and spiritual well-being.
So science has confirmed what yogis have known for centuries: yoga reduces stress. But how does it work?
The eight limbs of stress-relief
The traditional system of hatha yoga, as described in Patanjali’s Yoga Sutras, is composed of eight limbs of yoga. These eight limbs are the practices which lead a yogi on his path to enlightenment.
Guidelines for living, the yamas and niyamas, direct a practitioner in his behavior and thought. The yamas include compassion, honesty, non-stealing, self-control, and non-greed. The niyamas include cleanliness, contentment, discipline, self study, and recognition of a higher power. Living by these guidelines helps avoid the complications that dishonesty and lack of self-control bring about, as well as the negative thought patterns that lead to judgment, discontent and greed. By adopting an attitude of compassion for ourselves and all beings, we gain balance and peace of mind.
Physical postures, or asanas, promote strength, balance, flexibility, and the optimal functioning of the human body. Many poses directly calm the sympathetic nervous system. Forward bending poses which squeeze the abdomen against the thighs momentarily increase perceived blood volume and pressure, and the body responds by dilating blood vessels and decreasing the heart’s pumping volume to lower blood pressure. Slight prone backbends which put pressure on the abdomen (like bhujangasana, or cobra pose) have a similar affect. Heart-opening poses that place pressure on the adrenals mildly stimulate them, which can be helpful if chronic overstimulation of the HPA Axis has led to their dysfunction or fatigue. Other restorative poses, such as savasana (corpse pose) or viparita karani (legs-up-the-wall pose) allow the skeletal muscles to relax completely, releasing physical tension.
Breath control, or pranayama, can stimulate or calm the nervous system in addition to focusing the mind. While poor or abnormal breathing patterns can chronically overstimulate the autonomic nervous system (leading to anxiety or fatigue), deep and even breaths engage the diaphragm and induce a calming effect. In particular, inhaling and exhaling at a 1:2 ratio (in which the exhale is twice as long as the inhale), increases oxygen and decreases carbon dioxide in the body—this increase of oxygen is picked up by receptors in the brain stem and the aortic and carotid sinuses and initiates the body’s relaxation response by slowing the heart rate and reducing blood pressure.
Non-attachment, referred to as pratyahara, or withdrawal of the senses, is the practice of detaching one’s mind from external objects and occurrences. While practicing non-attachment, we may be aware of the object, but we control the mind’s focus to keep it from engaging with the object. This prevents us from becoming personally affected by what arises outside and allows us to maintain inner peace.
Meditation comprises the final three limbs: dharana, immovable concentration of the mind; dhyana, meditation on the profound or divine; and finally samadhi, union with the divine, to the degree that the concept of self dissolves as the practitioner becomes one with the universe. Meditation and deep relaxation practices quiet the mind and body and enhance the practitioner’s awareness of his entire being (corporeal as well as psychological and spiritual).
In a typical group yoga class, students practice postures and breathing, and often meditation. These three exercises alone can activate the body’s relaxation response and quiet the mind. The other limbs, especially the guidelines for living (yamas and niyamas) and the practice of non-attachment cultivate a peaceful presence that you can carry into all areas of your life, on and off the yoga mat. This state of peace is a foundation from which you can respond to situations in a healthful, objective and effective manner, instead of allowing them or their consequences to overwhelm.
Ross, A., & Thomas, S (2010). “The health benefits of yoga and exercise: A review of comparison studies.” The Journal of Alternative and Complementary Medicine, 16, 3-12.