Last month I attended a lecture delivered by Professor Zhang，a health expert，with the theme of"sitting for too long is bad for people's health"．From the lecture I learned that with the development of TV and computers，people today sit a lot more than ever before in history，which has a bad effect on their health．Not only can this habit make your neck or back ache，but it may also make you fat，increase the risk of heart disease and even death．To prevent these problems from happening，Professor Zhang suggested that those who sit too much，such as students and office workers，should form some good habits in life，such as going to school or work on foot or by bike rather than by car，taking the stairs instead of the elevator and standing while talking on the phone．He particularly reminded us that we students should stand up to do some activities during break time at school．