The new regulations are intended to prevent serious injuries - and the subsequent insurance payouts - resulting from what's known as kumitaiso, the building of human pyramids in gymnastic displays, the Kyodo news agency reports . Education Minister Hiroshi Hase told reporters that new rules on the activity, which is a popular feature of school sports days, would be in place by the end of March. Mr Hase, a former professional wrestler , said: "It involves the lives of children, and some of the casualties reported have led to serious injuries."