to keep their arms warm and loose so they don't cramp or get cold
Shooting sleeves.
there just basketball shooting sleeves
Those are actually called "shooting sleeves" and basketball players wear them to help maintain their shooting form.
Sweatbands, wristbands, shooting sleeves, and some have specially designed sneakers
to support an injury to the elbow or bicep or to keep sweat off their shooting hand
Sleeves
to keep their muscles/arms warmed up for the game
www.customsportssleeves.com
turtles
There are sun sleeves and there are compression sleeves. Sun Sleeves, like Crazy Arms, are made from UPF50+ fabric, that is designed to stay cool in hot sun, but they also serve to protect from wind chill on cold mornings cycling or out on morning walks. Compression sleeves are for use with high intensity work outs, and while they will likewise provide some protection from wind chill, they are not advised for longer exercise or activity. You can find out more at the Crazy Arms website.
on the Syracuse basketball team there is 18 players
Emos wear long sleeves to cover the cuts on their arms, forearms, and wrists.