Until Federer et al. came along, it was common knowledge that tennis was a young person's game. Competing in singles past your mid-twenties was unconceivable, a

Until Federer et al. came along, it was common knowledge that tennis was a young person's game. Competing in singles past your mid-twenties was unconceivable, at the highest levels. So, I guess the answer to all this is "fast progress in sports medicine"