Three Tai Chi instructors auditioned and were selected by one of the investigators (FL) to teach the classes. All instructors had a minimum of 10 years prior Tai Chi teaching experience and came from different ethnic and cultural backgrounds. The Tai Chi intervention was the classical 24-Form Yang style incorporating elements of balance, postural alignment, and concentration (China National Sports Commission, 1983; Yan & Downing, 1998).
Human growth hormone Mexico
Participants in the intervention group attended a 60-minute Tai Chi practice session twice a week for 6 months. The sessions consisted of a 15-minute warm-up, 30-minutes of Tai Chi, and a 15-minute cool-down period. During the practice, participants were led by an instructor and replicated the motions, postures, and speed of movement of the instructor.
Participants in the control group were instructed to maintain their routine daily activities and not to begin any new exercise programs. These participants were promised a 4-week Tai Chi program at the end of the 26-week intervention study period.

Measures
Background information. A short inventory was administered at baseline to assess demographic characteristics such as age, gender, education, income, and race/ethnicity.
Health-Related Quality of Life. HRQL was assessed with the Short-Form General Health Survey (Stewart et al., 1988) measured at baseline (Week 1), middle (Week 12), and termination (Week 24) of the study. The SF-20 was designed for use in clinical practice, research, health policy evaluation, and general population surveys. The SF 20 has proven useful in monitoring general and specific populations, comparing the burden of different diseases, differentiating the health benefits produced by different treatments, and in screening individual patients. The instrument comprises twenty items representing six domains of HRQL: physical functioning, role functioning, social functioning, bodily pain, mental health, and health perceptions. Each is defined below.
Physical function was assessed by six items assessing the extent to which health interferes with a variety of activities (e.g., carrying groceries, climbing stairs, and walking). Each item was measured on 3-point scale ranging from 1 (= limited for more than 3 months) to 3 (= not limited at all). Higher scores indicate better physical functioning.
Role functioning was assessed by two items assessing the extent to which health interferes with usual daily activity such as work or housework. Each item was measured on a 3-point scale ranging from 1 (= yes, for more than 3 months) to 3 (= no). Higher scores indicate better role functioning.

A single item determined participants levels of social functioning and measured the extent to which health interferes with normal social activities such as visiting with friends during past month. This item scale was measured on a 6-point scale ranging from 1 (= none of the time) to 6 (= all of the time) with higher scores indicating better social functioning.
Mental health was assessed by five items assessing general mood or affect, including depression, anxiety, and psychological well-being during the past month. Each item was measured on a 6-point scale ranging from 1 (= all of the time) to 6 (= none of the time) with higher scores representing better mental health.

The health perceptions dimension used five items designed to provide overall ratings of current health in general. Each item was measured on a 5-point scale from 1 (= definitely true) to 5 (= definitely false). Higher scores represent better health perceptions.

The scale of bodily pain was measured by a single item assessing the extent of bodily pain in previous four weeks. This item was measured on a 5-point scale from 1 (= none) to 5 (= severe). The bodily pain subscale was recoded so that a high score represents less pain.