I'm sort of low weighted, so I'm building up muscle recently. I set up my target towards Sampras or federer, but after I checked, Sampras weights only 77 kg? how come? Federer is 85 kg(so is Nadal, they are all around 185 cm) this strong guy only weight 77 kg? I mean, look at his heavy ass racquet, look at his boom serve and mighty overhead is this a wrong information?