How much are you really sweating when you exercise? You may not need to wring yourself dry to find out.
Researchers say they've developed a flexible device that sticks to the skin, analyses your sweat and sends the results to your smartphone.
That's not all. Researchers say the device – about the size of a quarter – offers insight into whether you need to drink more water or down an energy drink to boost electrolyte levels.
"The intimate skin interface created by this wearable, skin-like ... system enables new measurement capabilities not possible with the kinds of absorbent pads and sponges currently used in sweat collection," said John Rogers, lead author of a study reporting development of the "lab on the skin".
Read: Sweat is sexy
Rogers is a professor of materials science and engineering, biomedical engineering and neurological surgery at Northwestern University's McCormick School of Engineering in Evanston, Illinois.
The device is disposable, designed to be used once for a few hours while attached to the skin of the forearm or back.
A rich chemical broth
Why bother analysing sweat?
Because, Rogers said in a university news release, it's "a rich, chemical broth containing a number of important chemical compounds with physiological health information".
Read: 6 surprising truths about sweat
Researchers tested the device on two groups of cyclists and report their findings in the journal Science Translational Medicine.
They said the device gave accurate accounts of the acidity of sweat and concentrations of glucose, chloride and lactate.
To get the data, a user takes a smartphone photo of the device. An app then analyses that photo and displays the information.
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