Surely the days when tennis players were regarded as light weight athletes is now over. Matches played by today’s pros on the men’s side can last for well over 5 hours, sometimes in intense heat, and there is no let up or break. If you get a cramp (and leg cramps are really painful), too bad, you cannot get treated!
http://www.nytimes.com/2010/01/16/sports/tennis/16tennis.html?ref=tennis
The dark side to all this is that players’ injuries are becoming devestating. Nadal is in superb shape and the least likely athlete on earth to call a quitter. Yet he could not continue to fight during the Australian Open due to injuries caused by simply playing too hard. At some point the game is going to have to look at shortening the 5 setters or making the hard court surfaces easier on the body.