An influential medical report released in 1996 confirmed that daily accumulation of 30 minutes of moderate physical activity would significantly lower the risks of many chronic diseases (Physical Activity and Health: A Report of the Surgeon General. Atlanta, GA: U.S. 1996). The report also recommended walking as one of the best forms of exercise that suitable for both healthy and patient population in all ages. To meet the daily 30 minutes exercise guidelines, a popular health promotion campaign -- 10,000 steps of walking per day, has been widely implemented in western countries, and has been recently promoted by the Health Info-World of HK Hospital Authority. Some studies demonstrated various health benefits from regular walking. The most recent study by Murphy et al. (Med Sci Sports Exerc. 2002) provided an excellent example that, in a 6-week walking program (5 days per week), one single bout of continuous 30 minutes of walking per day yielded similar health benefits as three 10-minute walks per day. The exercise intensity for both walking exercises was 70-80% of maximal heart rate, and resulted in significant increase in HDL-cholesterol, and decreases in triglycerides and total cholesterol. Both walking exercises improved body composition significantly. Moreover, tension/anxiety were also decreases significantly. Similar health benefits were also noted by several other studies (Moreau KL, et al. Med Sci Sports Exerc 2001. Wullink M et al. Med Sci Sports Exerc 2001. O'Hara RB et al. ACSM's Health Fitness J 2000). In these studies, the walking intervention periods varied from 6 weeks to 24 weeks, and daily walking times varied from 20 minutes to 50 minutes. Exercise intensities varied from 50% to 70% of VO2max. However, the energy cost of a typical walking bout of HK adults is not clear. Since body composition of HK Chinese is different from those reported for westerners, it is reasonably believe that the energy expenditure of walking for HK Chinese is different from those found in the literature. The CVD benefits result from walking have not been reported for the Chinese population. These outcome measures derived from walking and Tai Chi have not been compared.

Tai Chi is an ancient form of Chinese fitness exercise. A number of studies have investigated the positive health improvement effects from Tai Chi for patients (Channer KS et al. Postgrad Med J 1996. Fontana JA et al. Nurs Clin North Am 2000. Lan C et al. Med Sci Sports Exerc 1999), as well as for healthy individuals (Lan C et al. Med Sci Sports Exerc 1998. Zhuo D et al. Can J Appl sport Sci 1984). These health benefits include an improvement of aerobic fitness (Lai JS et al. J Am Geriatr Soc 1995. Hong YL et al. Br J Sport Med 2000) and energy metabolism (Zhuo D et al. Can J Appl sport Sci 1984. Schneider D et al. Int J Sport Med 1991), muscular strength and balance (Hong YL et al. Br J Sport Med 2000. Chan WW et al. Phys Occup Ther Geriatr 2000. Schaller KJ et al. J Gerontol Nurs 1996), as well as mental control (Jin P. J Psycho-som Res 1992. Fasko Jr D et al. Clin Kinesiol 2001). Compared to walking, it is intuitively perceived that Tai Chi is characterized by lower exercise intensity and metabolic cost. But surprisingly, Lan et al. reported that the exercise intensity of a typical session of Tai Chi (24 minutes Yang style) exceeded 70% of maximal heart rate (Lan C et al. Arch Phys Med Rehabil 1996). However, the energy cost of this single bout of Tai Chi has not been investigated. Tai Chi and walking seem to provide similar benefits but has not been compared simultaneously except in one study. Jin reported that heart rate, blood pressure, and urinary catecholamine changes for Tai Chi were similar to walking at a speed of 6 km/h (Jin P. J Psycho-som Res 1992). However, the energy cost and CVD risk measures were not investigated in this study. Although both walking and Tai Chi are believe to have positive health benefits, the extents to which these exercises contribute to raising the energy metabolism as well as CV health improvement have not been documented. Which form of exercise would elicit higher energy demand and produce greater CV health effects? Currently no scientific data available to report such results for HK Chinese. Results from this study will be valuable for practitioners to provide quantifiable prescriptions for obese individuals for weight control, as well as for those who need to improve CV health.

AIMS

Increasing energy expenditure has been considered a crucial role for reducing obesity. Raising the level of energy expenditure has also been found to produce improvement in cardio-respiratory fitness and lowering CVD risks. However, the energy cost from Tai Chi and walking have not been fully studied and their training effects on CVD risks have not been compared. The purpose of the present study was to examine the level of energy expenditure of Tai Chi and walking, and to compare the training effects from Tai Chi and walking in terms of lowering CVD risks. Specific aims of the project were as follows:

1. To evaluate the changes of energy expenditure, aerobic fitness, body composition, SF-12, blood serum lipid profiles (total, LDL, and HDL-cholesterols), fasting blood glucose, dietary habits and physical fitness after the 12 weeks of Tai Chi and walking training, respectively.
2. to compare the effects of Tai Chi and walking exercises on improving energy expenditure, aerobic fitness, body composition, SF-12, blood serum lipid profiles (total, LDL, and HDL-cholesterols), fasting blood glucose, dietary habits and physical fitness after the 12 weeks of Tai Chi and walking training.
3. compare the energy metabolism during these two exercises at similar practice intensity (approximately at 50-70% of age-predicted maximal heart rate, and 30 minutes of exercise bout).