The aims of the study were to determine the effect of short-form Sun-style t'ai chi (SSTC) (part A) and investigate exercise intensity of SSTC (part B) in people with chronic obstructive pulmonary disease (COPD).Part A: after confirmation of eligibility, participants were randomly allocated to either the t'ai chi group or control group (usual medical care). Participants in the t'ai chi group trained twice weekly for 12 weeks. Part B: participants who had completed training in the t'ai chi group performed a peak exercise test (incremental shuttle walk test) and SSTC while oxygen consumption (VO 2 ) was measured. Exercise intensity of SSTC was determined by the per cent of VO 2 reserve.Of 42 participants (mean¡SD forced expiratory volume in 1 s 59¡16% predicted), 38 completed part A and 15 completed part B. Compared to control, SSTC significantly increased endurance shuttle walk time (mean difference 384 s, 95% CI 186-510); reduced medial-lateral body sway in semi-tandem stand (mean difference -12.4 mm, 95% CI -21--3); and increased total score on the chronic respiratory disease questionnaire (mean difference 11 points, 95% CI 4-18). The exercise intensity of SSTC was 53¡18% of VO 2 reserve.SSTC was an effective training modality in people with COPD achieving a moderate exercise intensity which meets the training recommendations.KEYWORDS: Anxiety and depression, chronic obstructive pulmonary disease, exercise capacity, exercise physiology, health-related quality of life, rehabilitation T 'ai chi, an exercise involving both upper and lower extremities, originated from China. T'ai chi is characterised by posture alignment, weight shifting and circular movements that incorporate elements of muscle endurance and strengthening, balance, relaxation and breathing control. The movements of t'ai chi are unique and are often described as slow, smooth flowing and graceful.T'ai chi has become a popular training mode in western countries and requires no exercise equipment or specific training venue and thus is easily implemented in the community. Currently, a number of t'ai chi styles are utilised, including Yang, Chen and Sun styles. Each of these styles is characterised by emphasis on slightly different forms (movements). The benefits of t'ai chi on balance, exercise capacity and muscle strength have been demonstrated in the healthy population [1,2] and people with chronic conditions, such as chronic heart disease [3] and osteoarthritis [4].In comparison with other styles of t'ai chi, shortform Sun-style t'ai chi (SSTC), also known as t'ai chi for arthritis, is a modified t'ai chi programme with 21 forms. This is one of the most common styles of t'ai chi and training courses for instructors are available worldwide. Each form can be broken down into several movements which are easy to teach and learn. Compared to some other styles of t'ai chi, SSTC involves less difficult movements, such as less deep-knee bending and single leg standing, which may make it more suitable for older people.Recent studies examining t'ai ...