Clothmos already attaq me in replies...OK. Ancient Germanics also went shirtless frequently even in cold weather, and always the bravest went shirtless or nude into battle. Berserks imported into ancient Near East as mercs are shown in stone reliefs as same
It's illogical for athletes to wear shirts especially in sports like tennis. No need to go full nude as in ancient Grek competitions, but wearing of shirts in sports is bizarre from natural point of view...holdover of clothmo Oriental prudery