Hatha Yoga involves physical postures (asanas), breathing techniques (pranayama), energy locks (bandhas), energy seals (mudras) and other practices to strengthen the physical body and to purify and balance one's energy to increase vitality, equanimity and joy of life.
The Sivananda and Ashtanga courses at our center are Hatha Yoga sequences of specific lineages. Where "Hatha Yoga" is indicated for a course, its sequence does not follow a specific lineage.
Initially, one’s hatha yoga practice brings a keener awareness of the physical body. The exercises keep one’s body young, dynamic, supple, strong, and healthy. All yoga postures, combined with proper breathing, improve the circulatory, endocrine, and nervous systems. Digestion and assimilation are also stimulated as well as the elimination of toxins. The lymph system, the body’s defense mechanism, is thus far better able to prevent the onset of illness and will accelerate recovery when symptoms begin.
By maintaining one’s physical body at its optimal level in a focused and mindful way, one can arrive at a deep tranquility to better mitigate stressful situations and to remain centered regardless of the ups and downs of daily living.
From a yogi's point of view, hatha yoga touches on a spiritual realm by working on the vital energy or pranic system through the purification of energy channels (nadis) to bring the alternating energies of prana and apana together in a specific manner to trigger a spiritual awakening. For a more in-depth explanation, read Fredric's article "What is Hatha Yoga?"