Swiss researchers have found that tai chi practice can reduce psychobiological stress reactivity in healthy subjects. A group of 70 healthy men and women were randomly assigned to either tai chi classes or a waiting list. After three months, participants underwent a standardised psychosocial stress test, combining public speaking and mental arithmetic in front of an audience. Compared with controls, tai chi participants exhibited significantly lower stress-induced increases in heart rate and levels of salivary cortisol, as well as lower salivary a-amylase levels. The tai chi group also reported a smaller increase in perceived stressfulness and maintained a higher level of calmness in response to induced stress. (Taiji practice attenuates psychobiological stress reactivity–a randomized controlled trial in healthy subjects. Psychoneuroendocrinology. 2012 Aug;37(8):1171-80).