Women's quarters show fitness key to longevity NEW YORK (Reuters) - Victoria Azarenka paid tribute to the old brigade at Flushing Meadows after she joined five players over the age of 30 in the women's quarter-finals of the U.S. Open. The second-seeded Belarussian withstood a stern challenge from Serbia's Ana Ivanovic to post a 4-6 6-3 6-4 victory and ensure a last eight meeting with unseeded Slovakian Daniela Hantuchova on Wednesday. Quarter-finalists Hantuchova, Serena Williams, China's Li Na and Italians Roberta Vinci and Flavia Pennetta are all 30-plus, and the 24-year old Azarenka said their lengthy careers were a reward for their high levels of fitness. "Everybody's taking much more care of their bodies to be able to play longer," said Azarenka. So much more fitness has been introduced, nutrition, all those components that women and men are paying so much more attention to. It's a great thing if we have longer careers. Azarenka was unconcerned by having to play on consecutive days after rain forced her fourth round match, originally set for Monday, to be postponed. Rather, she was focused on advancing to a second consecutive U.S. Open final against reigning champion Williams thanks to improved serving and her renowned fighting spirit. "I have never aced so much in my life," said Azarenka, who has recorded nine aces through four rounds. I'm not a big server, but I think it's getting better. Daniela is playing incredible tennis right now, so it's going to be another tough battle of taking your chances, playing your game and being in control. Wednesday's other quarter-final will be the all-Italian matchup between Vinci and Pennetta. "It is going to be a really tough match for both of us," Pennetta said. I've known her since 20 years or more because we live almost in the same place. It was just 35 to 45 kilometers, my house from her house. I'm supposed to lose because she is better than me in this moment. I don't have nothing to lose.