I mean physically, all round (arm, leg, core etc.) strength? Nadal doesn't look as bulky these days. I've seen some pictures of Murray where it looked like he had been working out pretty hard... but he still looks like someone has photoshopped a scrawny guy's head onto someone else's body. Tsonga doesn't look so toned but he is pretty big and shows his power on court. But also how important is muscular strength? Would players be better off improving endurance and technique?