KumiTaisou(A set gymnastics)

"
A set gymnastics,
On the basis gymnastics,
Without using tools generally
Is a group art to be performed using the human body.
In Japan
It is a kind of mass game be showcased often in sports festival and field day of school.
Alias "assembly gymnastics"
Or for short "assembly"."
(From Wikipedia)

Although at one time was waning accident students serious injury is or place,
Where to revival seems to have increased recently.