Injuries from kumitaiso, a form of physical education in which people use their bodies to express shapes, including human pyramids, numbered 432 cases in the last fiscal year at elementary and junior high schools in Chiba Prefecture, officials said.

Of the figure, 112 cases involved broken bones, the Chiba Prefectural Board of Education said Tuesday, highlighting safety concerns that human pyramids and other extreme showpieces staged by schoolchildren during undokai sports days could have serious consequences.

According to the board, some cities in Chiba Prefecture, including Kashiwa, Nagareyama, Noda and Abiko, are considering entirely abolishing kumitaiso, or at least part of the moves that may involve safety risks.

Chiba Prefecture acted proactively on the issue given the recent rise in the number of injuries from those demonstrations nationwide. It conducted a survey in January and February on the prefecture's public elementary and junior high schools.

Of the 1,358 schools polled, 706 answered they staged kumitaiso events last year. Injuries occurred at 183 elementary schools and 50 at junior high schools, the survey found.

While many schools and parents have voiced safety concerns, some teachers are apparently keen on posting photos and videos online of students forming human pyramids, some with as many as 10 tiers.

In spite of the dangers, schools have students build the human pyramids for a sense of unity and achievement, according to education experts. They also pointed out that those activities are forced on all students even if they are unwilling participants.