Other things such as the length of an arm wrestler 's arm , his\/her muscle and arm mass\/density , hand grip size , wrist endurance and flexibility , reaction time , as well as countless other traits , can add to the advantages of one arm wrestler over another . Other factors such as the length of an arm wrestler 's arm , his\/her muscle and arm mass\/density , hand grip size , wrist endurance and flexibility , reaction time , as well as countless other traits , can add to the advantages of one arm wrestler over another .