I am going to assume you are referring to the straps used to keep gymnasts from falling off the bars while learning difficult skills. All of the straps I've seen are made of nylon webbing that is the same type used in rock climbing and mountaineering. It is extremely strong and able to hold up the extreme forces and heavy use in gymnastics. The straps are made in a variety of sizes to accommodate gymnasts of different ages and sizes.
There are different kinds of guards: wrist guards, or grips "palm guards" Grips are made of touch leather and are used for uneven bars, parallel bars (p-bars), rings, and high bar. Are used to grip the equipment and help protect hands from severe calluses and "rip" (open calluses that rip on your hands) Wrist guards which are also made out of leather, are made for all the evens except the ones listed above. They are used to protect the wrist from certain movements and help support wrists.
mouth guards are made of rubber
The ancient Greeks invented gymnastics
He has made gymnastics his whole life.
1972 by cellin stone
The ancient Greeks
They were originally made of hay.