Heart patients should interrupt sedentary time every 20 minutes with a seven minute bout of light physical activity to prolong life, according to a study. Previous research has shown that being sedentary for long periods could shorten life but taking breaks to move around may counteract the risk, particularly if it means burning more than 770 kilo calories (kcal) a day. This study, presented at the annual Canadian Cardiovascular Congress in Toronto, investigated how many breaks, and for what duration, are needed to expend 770 kcal. -- PTI