Painful irritation or swelling of tendons due to overuse is

Overuse or strain on a joint can irritate tendons and result in tendinitis. Tendinitis is inflammation or irritation of a tendon — the thick fibrous cords that attach muscle to bone. The condition causes pain and tenderness just outside a joint.

If it's a smaller child or infant, place one on the middle of the chest and on the child's back. (if it is a bigger child with enough room for two, place one on the upper right/your left of the chest, and one on the lower left/your right) the pads should never touch each other. 

False- i believe that would be the definition of balance