Does anyone know the purpose of the "bunge cord-like" bands that college and nfl players wear mostly on their arms, most are just above the elbow. They are not sweat bands, they are a rubber-like substance. There is no advertising, they are round and about 1/4 to 1/2 inch in diamater, so no advertising is on them. I assume they are training or health issue related... but what is their purpose?