Comparing Effects and Neural Mechanisms of Tai Chi and Light-to-Moderate Intensity Aerobic Exercises

In this three-year project, investigators will target on sedentary middle-aged and older adults with cardiovascular risks, prescribe 24-week Tai Chi or aerobic exercises and examine: 1. Whether both exercises are effective to reduce cardiovascular risks, prevent leukoaraiosis and associated declines in physical and psychological functions at Week 12 and 24; 2. Will Tai Chi exercises be more effective on improving psychological health (cognition, psychological well-being, and exercise self-efficacy) than aerobic exercises at Week 12 and 24? If yes, are these effects mediated by specific brain structural and functional mechanisms? 3. Will aerobic exercises be more effective on improving physical health (motor functions, physical fitness, and heart rate variability) than Tai Chi exercises at Week 12 and 24? If yes, are these effects mediated by other specific brain structural and functional mechanisms? 4. After 12 and 24 weeks of Tai Chi and aerobic exercises, what are the relationships between reduction of cardiovascular risks and changes in brain structure and functions? An assessor-blind randomized controlled clinical trial will be used. Based on known effect size of Tai Chi exercises on cognitive function (please refer to CM03, pages 9-10), 120 sedentary middle-aged and older adults with cardiovascular risks will be recruited and randomly assigned to the Tai Chi, Aerobic, or Control (usual care) group. The Tai Chi and Aerobic groups will receive three one-hour exercise sessions weekly for 24 weeks, supervised for the first 12 weeks and unsupervised for the next 12 weeks. The Control group will maintain the original life style. Clinical measures of cardiovascular risks and blood markers, brain structures and functional images, psychological (cognitive, psychological well-being and exercise self-efficacy) and physical (motor functions, physical fitness, and heart rate variability) functions will be collected at baseline, Week 12, and Week 24 to compare differences among the three groups across the three time points. Investigators will also examine the interrelationships of changes in brain structural and functional organization with changes in other measures, in an effort to understand the neural mechanisms of exercise effects.