The following is a learned article from
[Medical Editor: William C. Shiel Jr., MD, FACP, FACR]. (I have added highlights, emphases and broken up long into shorter paragraphs)
Who is Richard Weil? He is an exercise physiologist and certified diabetes educator. He is director of the New York Obesity Research Center Weight Loss Program at St. Luke's Roosevelt Hospital Center in New York City. He is the author of dozens of articles on exercise and health and has written or contributed to the exercise chapters of several books, including Time-Life's "The Gym Workout." He has appeared on many TV and radio shows in the USA.
What are the benefits of tai chi?

 In China, it is believed that tai chi can delay aging and prolong life, increase flexibility, strengthen muscles and tendons, and aid in the treatment of heart disease, high blood pressure, arthritis, digestive disorders, skin diseases, depressioncancer, and many other illnesses.

 Unfortunately, there hasn't been a good deal of scientific evidence to support all of these claims. In a special study of tai chi called a meta-analysis, where many studies on one subject are reviewed, the author concludes that although there is some evidence to support the positive effects of tai chi on health,fitness, and balance and falling, many of the studies are limited by small numbers of subjects and wide variation in the type and duration of tai chi used. Bearing these limitations in mind, here are some of the documented benefits.
Balance and falling  
Most of the research on tai chi has been done in older individuals in the area of balance and fall prevention. This area of research is important because fall-related injuries are the leading cause of death from injury and disabilities among older adults. One of the most serious fall injuries is hip fracture; one-half of all older adults hospitalized for hip fracture never regain their former level of function.

Because tai chi movements are slow and deliberate with shifts of body weight from one leg to the other in coordination with upper body movements (sometimes with one leg in the air), it challenges balance and many have long assumed it helps improve balance and reduce fall frequency. This assumption has been credited and strongly supported by some research.
One study compared men age 65 and older who had more than 10 years of experience practicing tai chi and no involvement in any other regular sports and physical activity, with similar-aged men who had not practiced tai chi or any other physical activities (they were sedentary). It was found that the men who studied tai chi performed better on tests ofbalance, flexibility, and cardiovascular function.
In another study involving 22 men and women aged 22 to 76 years with mild balance disorders, it was found that eight weeks of tai chi training significantly improved function on a standard balance test (called the Romberg test).
Fear of falling and improvement in self-confidence
In an interesting twist on studies of falling, researchers found that the frequency of fear of falling was reduced from 56% to 31% in a large group of adults 70 years and older who practiced tai chi regularly. Confidence about not falling, and self-confidence in general, may be an unintended benefit of tai chi but one that is certainly worth pursuing.
In a similar tai chi study of older adults, 54% of the subjects who practiced tai chi attributed their improved sense of confidence to improved balance. The authors concluded that "when mental as well as physical control is perceived to be enhanced, with a generalized sense of improvement in overall well-being, older persons' motivation to continue exercising also increases."
Strength and endurance
One study took adults in their 60s and 70s who practiced tai chi three times a week for 12 weeks (60-minute classes). These adults were given a battery of physical-fitness tests to measure balance, muscular strength and endurance, and flexibility before and after the 12 weeks. After just six weeks, statistically significant improvements were observed in balance, muscular strength, endurance, and flexibility measures. Improvements in each of these areas increased further after 12 weeks. The authors of the study concluded that tai chi is a potent intervention that improved balance, upper- and lower-body muscular strength and endurance, and upper- and lower-body flexibility in older adults.
Aerobic capacity
Aerobic capacity diminishes as we age, but research on traditional forms of aerobic exercise show that it can improve with regular training. In another meta-analytic study, researchers looked at seven studies focusing on the effects of tai chi on aerobic capacity in adults (average age 55 years). The investigators found that individuals who practiced tai chi for one year (classical yang style with 108 postures) had higher aerobic capacity than sedentary individuals around the same age. The authors state that tai chi may be an additional form of aerobic exercise.
Walking speed decreases with age and research suggests that it may be associated with an increased risk of falling. In one study, however, it was found that individuals who practiced tai chi walked significantly more steps than individuals who did not. Walking has clearly been associated with a decreased risk of cardiovascular disease, diabetes, and other chronic illness, and so if tai chi can improve walking, then it's certainly worth giving it a try.
Fibromyalgia (FM) is one of the most common musculoskeletal disorders and is associated with high levels of impaired health and painful symptoms that frequently flair up without relief. The cause of FM is unknown, and there is no known cure. In a study of 39 subjects with FM who practiced tai chi twice weekly for six weeks (one-hour classes), it was found that FM symptoms and health-related quality of life improved after the study. This could be good news for many other individuals who suffer from this disorder.

The demands of living are stressful for adults of all ages. Although one cannot directly point to studies showing areduction in stress from practicing tai chi (though in one study subjects who practiced tai chi reported that mental control wasone of the benefits), the breathing, movement, and mental concentration required of individuals who practice tai chi may be just the distraction you need from your hectic lifestyle. Themind-body connection is one that deserves special attention, as it has been reported that breathing coordinated with body movement and eye-hand coordination promote calmness.
I know that when I practice yoga or tai chi, the inner sense of peace and calm is indisputable, and so I suggest that you give tai chi a chance if you're looking for a creative and physically active way to improve how you mentally and physically respond to stress.
Some more reasons to practice tai chi:
   Movements are low-impact and gentle and put minimal stress on your muscles and joints.
   The risk of injury is very low.
   You can do it anywhere, anytime.
   It requires very little space (no excuses apartment dwellers!) and no special clothing or equipment.
   You do it at your own pace.
   It's noncompetitive.
   It can be done in groups or by yourself (find a tai chi instructor to come to your workplace at lunch hour!).
   There are lots of movements to keep you interested, and as you become more accomplished you can add those to your routine.   
How much tai chi should I do?
There's not enough research to suggest what the optimal dose of tai chi is to accrue benefits. Studies have shown effects with as little participation as one hour of training per week, although, as in any new activity (such as dancing) there is a sharp learning curve in the beginning, and many individuals might find participating two to three times per week, at least in the beginning, is probably a more effective dose. It is the conventional wisdom in tai chi circles that a person needs at least one year of tai chi before one becomes proficient.
How do I get started with tai chi?
Tai chi is becoming more popular in the United States as Americans look for new and different ways to exercise. Video tapes are one way to get started with tai chi. Check and for a selection of tai chi tapes; everything from tai chi for seniors to urban tai chi. Although I frequently recommend video tapes, you may be better served learning tai chi hands on...that is, with an instructor.
The movements should be done properly, and a watchful instructor might be better at helping you than a video tape if you have difficulty with movement. Check your local community recreation center, health club, martial arts studio, Y, or senior center for tai chi classes. Of course, if there are no classes in your area, then a video tape is the next best thing.
As I mentioned, there are several styles of tai chi. The wu style seems best for balance and fall prevention, but your choices may be limited, and so I suggest that you practice whatever is available to you. As tai chi gains in popularity, your local options may increase as well. However, since all styles of tai chi involve slow, flowing movements with attention to breathing, you'll benefit from whatever style you can find
What clothing should I wear for tai chi?
Comfortable and loose-fitting clothing that won't restrict your movements are best. Sweatpants, tights, or leotards, and a T-shirt will do. Although it doesn't look like very arduous work (because the movements are so slow), you may work up a sweat, and so overdressing is not recommended.
What precautions should I take before practicing tai chi?
Tai chi is gentle enough for almost everyone. However, if you have arthritis that affects your joints (theArthritis Foundation recommends tai chi), orthopedic conditions that limit your mobility (back pain, sprains, fractures, and severe osteoporosis), if you're pregnant, if you have a hernia, or if you have any other medical condition that might be affected by exercise, then it's a good idea to speak with your doctor before you try tai chi. If you're concerned about the class that you're considering, then watch the class or speak with the instructor before you start. You want to feel comfortable with the activity, so speak up! What have you got to lose?
That's tai chi. Practicing it regularly can improve your aerobic capacity, muscular strength, flexibility, and balance; and it can improve your well-being and decrease your stress. It's a martial art that has been practiced for centuries by millions of Chinese. Could all of them be wrong? My suggestion is to give it a try. You've got a lifetime of fitness ahead of you, and so adding something new and different to your fitness skills that has this much potential is worth a try, and certainly worth the effort!
What resources are available to people interested in tai chi?
Medically reviewed by Jonathan Miller, MD; Board Certified Physical Medicine and Rehabilitation
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