What Is It?
Yoga is an ancient philosophy of life as well as a system of exercises that encourages the union of mind, body, and spirit. In fact, the word yoga is derived from the Sanskrit word meaning "yoke" or "union." The ultimate goal of yoga is to achieve a state of balance and harmony between mind and body.

There is evidence that yoga was practiced as early as 5,000 years ago, although the first written description is found in the Yoga Sutras, a book from the second century B.C. that is partially attributed to the Indian physician and Sanskrit scholar Patanjali. The Yoga Sutras describe a multi-fold path to spiritual enlightenment that includes Hatha yoga, the system of physical exercises, breathing techniques, and meditation that is most often followed by Western yoga practitioners today. (Other forms of yoga include Bhakti, Jnana, Karma, Laya, and Raja.) All types of yoga subscribe to the belief that the body and mind are seamlessly connected, and that, for optimal health, they must be in a state of balance.

How Does It Work?
What sets Hatha yoga apart from some other forms of yoga and general exercise programs is that it places an equal emphasis on mental and physical fitness. This mind-body integration, proponents believe, is what helps Hatha yoga practitioners feel calmer and more "centered," and is why it's often recommended for stress reduction.

Hatha yoga concentrates on three areas: pranayama (breathing), asanas (postures), and dhyana (meditation). The controlled breathing of pranayama helps to focus the mind and is important for relaxation and meditation. Its deep, slow breathing patterns have a beneficial effect on the respiratory system: Studies show that people who do yoga regularly have lowered breathing rates and increased lung capacity. The postures, which include standing, balancing, forward and backward bends, and twists, strengthen the body, increase flexibility, and encourage relaxation. In addition, Hatha yoga has been shown to improve posture and increase circulation. Dhyana, the meditative aspect of yoga, calms and focuses the mind. All three practices build on and complement one another.

Although scientists don’t know exactly how yoga produces its physiological benefits, some speculate that it does so primarily by reducing stress. It may also promote the release of endorphins, the body's natural painkillers.

What You Can Expect
Hatha yoga can be learned from books or videotapes, and easily lends itself to practice at home. However, beginners initially will be better served by taking classes with a trained yoga teacher. A good teacher can help you learn proper breathing and meditation techniques and specific postures, and can help you address your particular needs and physical limitations. Classes generally last 60 to 90 minutes, and beginners usually take one or two classes weekly.

A Hatha yoga class may begin with a period of quiet. The teacher will then take you through gentle warm-up exercises and into a series of postures, which are each held anywhere from a few seconds to several minutes. As your abilities improve, you will be taught progressively more difficult postures. Movement throughout the class should always be gentle, never painful.

Proper breathing, through the nostrils, is emphasized throughout the classes, and the teacher may suggest that you focus on exhaling during certain postures and on inhaling during others. A class generally ends with a period of deep relaxation, with students lying comfortably on the floor.

Whether you attend classes or practice yoga at home, it is important to work in a warm, quiet room. Be sure to wear loose, comfortable clothing so you can move easily. While classes often provide a special "sticky mat," which helps prevent slipping, you can use a blanket or towel for the same purpose. It is also recommended that you practice yoga barefoot.

There are no hard and fast rules about how often to do yoga, but regular practice will help you achieve the full benefits. Many teachers recommend a 20- to 30-minute routine every day. For comfort's sake, always practice on an empty stomach. Many people prefer a yoga session upon awakening in the morning; others find that doing yoga before bed helps them to fall asleep.

Health Benefits
A substantial amount of research has been conducted on the health benefits of yoga, and further studies are ongoing. In addition to improving the body's strength, flexibility, coordination, and range of motion, yoga has been shown to decrease blood pressure, slow respiratory rate, improve the fitness of the heart and other muscles, and reduce stress and anxiety.

Studies have shown yoga to be particularly helpful for musculoskeletal ailments: A study published in the Journal of the American Medical Association in 1998 showed that yoga reduced pain and increased grip strength in people with carpal tunnel syndrome. Another study, published in the Journal of Rheumatology in 1994, showed that yoga reduced pain and increased range of motion in people with osteoarthritis of the hands.

Because it promotes relaxation, yoga also aids sleep and digestion. While yoga on its own is not a cure for any condition, it is often recommended as a complementary therapy for cancer, arthritis, asthma, diabetes, depression, fibromyalgia, and migraines. It can also be beneficial during pregnancy.

How To Choose a Practitioner
Most health clubs, YMCAs, YWCAs, and community centers offer Hatha yoga classes. Among the more popular types of Hatha yoga classes are:

Iyengar, which stresses precision and uses props.

Astanga (or "power yoga"), which is strenuous and for those who seek an aerobic workout in addition to yoga's other benefits. It's not for those out of shape.

Kundalini, which emphasizes breathing and chanting.

Viniyoga, the precursor of Iyengar and Astanga, which stresses harmonious sequences of postures. To find classes, ask for references from friends who study yoga and don't be afraid to shop around. Many centers allow prospective students to take a first class for free. Others offer "sampler" days when new students can try out shorter versions of regular yoga classes.

Because yoga instructors are not medical professionals, no licensing is required. Certification can be obtained through some yoga schools, however. Look for a teacher who has at least several years of experience and who continues to study and practice yoga actively.

While classes are recommended for beginners, there are also many yoga books and videotapes available to guide you.

Cautions
Before starting a yoga class, be sure to tell your teacher about any concerns or physical limitations you may have.

Always warm up gradually and work at your own pace. While some stiffness may occur after the first classes, you should not feel pain.

Avoid upside-down postures, such as shoulderstands or headstands, if you have high blood pressure, glaucoma, or a hernia.

If you are pregnant, tell your instructor, so he or she can modify postures for you. If you prefer, there are special yoga classes available for expectant mothers. Avoid postures that put pressure on the uterus.

Avoid or alter back-bending postures if you have disk or other back problems.

If you’re not in good athletic shape, think twice before you enroll in currently popular Astanga or "power yoga" classes, which can be physically challenging.