This band collects sweat that escapes around your wrists and ankles.
Jo Song-won & Song Rui-hao
A rubber band with a color-changing sensor built into it can measure the acidity of sweat coming from your skin, indicating how hard your muscles are working.
The device could be used to improve worker safety in physically demanding jobs, such as the construction industry, and could help sports athletes optimize their training, they said. John Rogers At Northwestern University in Illinois.
“If you see your pH dropping to a very low level, it’s probably a good idea to stop exercising,” says Rogers. “Otherwise, your muscles will get sore. But it’s also a sign that you’re not exercising enough.”
During high-intensity exercise, your muscles produce a chemical called lactic acid. As you continue to exercise, the levels of this chemical in your blood begin to spike as your body approaches its endurance limit. This can lead to a burning sensation in your muscles, sudden loss of energy, and extreme fatigue. The fitter you are, the longer and harder you can exercise before your blood lactic acid levels start to rise to high levels.
For this reason, blood lactate levels in elite athletes are often monitored during training. This requires obtaining a sample from a finger prick, so many groups are trying to develop noninvasive alternatives.
The solution Rogers and his team came up with is an elastic band with a series of small reservoirs that fill with sweat at different intervals. Inside each reservoir is a sensor that changes color depending on things like lactate concentration or the acidity of the sweat. The results are read by taking a picture with a smartphone or attaching an electronic monitor.
In a study testing sweat monitors on 12 volunteers while they rode exercise bikes, the researchers found that while lactate levels in sweat did not match blood lactate levels, the acidity of the sweat did.
“What we found was that sweat pH was a better indicator of blood lactate concentration than sweat lactate concentration,” says Rogers.
However, this only applies to sweat coming from the skin near the working muscles, which was monitored by wrapping the band around the ankle. Measurements made with the band around the cyclist’s wrist did not reflect blood lactate levels.
“This isn’t the answer to everything people want to know, but it does provide new types of data that weren’t available before,” Rogers said.
A company he co-founded, Epicore Biosystems, already produces a disposable patch that measures sweat loss and electrolyte levels, which it says can help prevent dehydration. Rogers says some companies are using the patch to monitor athletes and people who exercise in very hot and humid environments.
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