Sweat monitor could reveal when you are exercising too hard

A band that measures the acidity of sweat could flag if athletes or manual workers are overexerting themselves

By Michael Le Page

4 September 2024

This band can collect sweat excreted around the wrists or ankles

Soongwon Cho & Ruihao Song

Elastic bands embedded with colour-changing sensors can reveal how hard muscles are working by measuring the acidity of sweat on skin.

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 at Northwestern University in Illinois.

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“If you see your pH dropping down to very low levels, it’d be a good idea to stop working out,” says Rogers. “Otherwise you end up with sore muscles. But it’ll also tell you if you haven’t worked out enough.”

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.

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.