Arm swing is key to stabilizing the body. These lessons deter flailing and other excessive movement.
The primary role of the arms in running is to stabilize the body. Young children often have excessive movement when they run because they have not yet developed awareness and command of their bodies. Give them feedback on their movement patterns, always being positive and never critical, to help them develop awareness and control.
View the Form 101: Arm Movements video for the five essentials of a good arm swing for elementary school children to explore.