It's no stretch. Medical practitioners are reminding Hongkongers about basic exercise principles after dozens of residents have injured themselves practising yoga since the beginning of the year. 'If you're not prepared for it, or you don't do it properly, you can cause injury for sure,' said Tim McCosker, a registered physiotherapist in Hong Kong. A person can't 'go from zero to hero in the space of a week or two', he said. 'You have to do it gradually just like any other training programme.' Also, 'people should ask for other people's qualifications. If they're paying money and they're going into a gym ... then they should ask, 'What training have you had to teach me this stuff?'' Added Priscilla Poon, vice-president of operations for the Hong Kong Physiotherapy Association: 'We think that yoga is still a type of activity which can improve your strength and also improve your physique.' Nevertheless, she urged those interested in yoga 'to have a good instructor and know your body quite well. You have to do yoga based on the principles of stretching exercises - that means you have to do it slowly, and with sustained movement, no jerky movements should be allowed. And you have to do it based on your own ability or capabilities'. Chiropractor Claudia Ng, said people should tell their doctor before they begin yoga classes, 'and have a good understanding and proper analysis of their structure and body mechanics. And see whether yoga is really the exercise of choice'. If given the green light, a patient should ask their doctor for stretching advice, and then begin stretching for a month before joining a class. Dr Ng also suggested that people might want to think again about shedding their shoes while practicing yoga poses on a thin mat. 'Just about 80 per cent I see have flat feet or ... in-rolling of the ankles. That alone is enough reason for not doing any [standing] exercises in bare feet ... Over a period time, they could get hurt.' Dr Ng said she encourages many of her patients to do yoga. 'Yoga is a great form of exercise because it incorporates stretching, strengthening, endurance, balance, and co-ordination,' she said.