Uninformed people may believe the stereotype that chess is a game played by old men in the park but the reality is that it takes a tremendous amount of mental and physical stamina to play elite level chess; that is why most of the top players in the world are in their teens or twenties and why the performance level of elite chess players tends to decline after the age of 40.
Bulgarian Grandmaster Kiril Georgiev has just accomplished a remarkable feat of mental and physical endurance, setting a world record by playing 360 opponents at the same time! He scored 284 wins, 70 draws and just six losses (88%) in a simultaneous exhibition that lasted for more than 14 hours. He had to walk about half a kilometer just to make one move on each board, which is why part of his training for this event consisted of walking for five to six hours a day.
I am a USCF rated expert who has done simultaneous exhibitions of between one and three hours against 10-30 players, so I can say from firsthand experience that what Georgiev did is incredible.