Andy Murray says he has undergone "sweat testing" after recent issues with cramping during matches.

Murray is now "looking for answers" as he builds up to next week's US Open in New York.

"We're trying to understand why exactly it's happening," he said.

"I'm doing sweat-testing in these conditions to see if anything's changed in that respect because the sports drinks and the electrolytes and stuff that I drink are made specifically based on my sweat tests.

"I haven't done sweat testing for quite a number of years, so we're just seeing if anything has changed in that respect.

"Some people think it can be hydration-related, conditioning-related, stress-related, whether you've not eaten the right stuff, there can be a number of factors that go into it. It could be an underlying illness that's there, so we're just trying to get some answers."

Murray, who won the US Open in 2012, will get his Flushing Meadows bid under way on Monday against Argentine 24th seed Francisco Cerundolo.

The 35-year-old is realistic that there won't be an immediate solution to his cramping issue, but hopes there is a chance of some improvement.

"If it's conditioning-related, I'm not going to get fitter in the next few days.

"But if there is something else there that I could potentially change, whether it's eating or drinking or illness or something, then there's the possibility that could change pretty quickly."