大象传媒

You may have seen noticed some Olympians - including the American swimmer Michael Phelps - with dark purple spots on their backs and shoulders.

There've been plenty of pictures online - and it's provoked a lot of comment. It's the result of "cupping" - a Chinese therapy that uses cups to produce suction, pulling the skin away from the body. It's said to promote blood flow and supposedly ease aches and pains - but experts say there's no scientific proof it works. In fact, some doctors say it's "nonsense". The purple spots typically fade after three or four days.

Jonathan went to meet Dr Rizwhan Sulliman to find out what it's all about...