Andy Murray has vowed to find an answer to the cause of the cramps that arose in his first-round win over Robin Haase at the US Open.
Murray progressed to the second round at Flushing Meadows with a 6-3, 7-6 (8-6), 1-6, 7-5 win over the Dutchman but suffered terribly with cramps.
And the 2013 Wimbledon champion, who won the US Open back in 2012 after his Olympic success in London, will seek clarification on the potential issue.
"I felt extremely good before the match, and I did train very, very hard to get ready for the tournament," he said.
"For me it was unexpected, and therefore quite difficult mentally to deal with. Sometimes it can happen in one area of your body but when it starts to go everywhere, you don't know exactly where it's going to creep up next.
"When you stretch one muscle, something else then cramps, too. It was tough and very unexpected, especially after an hour and a half.
"So it's unlikely, I would say, that it's down to poor physical condition, because I have trained and played matches. I don't know if it's something I have done in the last few days that's been wrong or not, but I need to try and find out why.
"It's not the worst I have ever felt, but it's the worst I have ever felt after an hour and a half of a tennis match. That's what was worrying about it, is it came after such a short time."
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