Britain's Andy Murray says his body is "responding well" to the rigours of Grand Slam matches as he prepares to face Italy's Matteo Berrettini in the US Open third round on Friday.
"I'm not having to worry about waking up the next day with something that is going to really impact me or hamper my tennis," said the 35-year-old Scot.
Fellow Briton Jack Draper, 20, appears in the third round of a major for the first time when he plays Russia's Karen Khachanov at about 20:00 BST.
"All the hard work that I've put in the last few years is for these moments," said Draper after beating Canadian sixth seed Felix Auger-Aliassime in the second round on Wednesday.