This could happen in many cases, but drill teams often do this.
Bicycle clip
What extra bones ?
a group of horses is called a herd, and a male horse is a stallion
It is called an arena. For Western riders, it's often called a pen.
The skilled horse riders who were nomads were mosveans.
Horse riders in competition are "equestrians", just atop a horse is the adjective "mounted".
couriers moof couriers
Moof counries
A group of horses is called a herd.
It is generally best practice to have all riders mounted before asking the horse to canter. This ensures safety for both the riders and the horse. However, if some riders are dismounted, it is best to have the horse walk or stand still until all riders are ready.
The person who rides a horse would be called either a equestrian or horse rider, but if the person only rides in shows, they may also be called show riders.
There is no typical name for it besides helmet, but it can also be called an equestrian helmet