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<\/div>This band can collect sweat excreted around the wrists or ankles<\/p>\n
Soongwon Cho & Ruihao Song<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n
Elastic bands embedded with colour-changing sensors can reveal how hard muscles are working by measuring the acidity of sweat on skin.<\/p>\n
The device could be used to improve worker safety in physically demanding jobs, such as the construction industry, as well as to help sportspeople optimise their training, says John Rogers<\/a> at Northwestern University in Illinois.<\/p>\n \u201cIf you see your pH dropping down to very low levels, it\u2019d be a good idea to stop working out,\u201d says Rogers. \u201cOtherwise you end up with sore muscles. But it\u2019ll also tell you if you haven\u2019t worked out enough.\u201d<\/p>\n During high-intensity exercise, muscles produce a chemical called lactate. With continued exercise, levels of this in the blood start to shoot up as people near their limits of physical endurance. This can lead to a burning sensation in muscles, a sudden loss of energy and extreme fatigue. The fitter people are, the longer and harder they can exercise before blood lactate rises to high levels<\/a>.<\/p>\n For this reason, the blood lactate levels of elite athletes are often monitored during training. This requires getting samples from a finger prick, so many groups are trying to develop a non-invasive alternative<\/a>.<\/p>\n <\/p>\n The solution Rogers and his team have come up with is an elastic band with a series of tiny reservoirs that fill with sweat at different intervals. Inside each reservoir is a sensor that changes colour depending on things such the concentration of lactate or the acidity of sweat. The results are read by taking a photo with a smartphone or attaching an electronic monitor.<\/p>\n