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Biosensor That Warns when Athletes are about to 'Hit The Wall'

A new biosensor, designed by researchers Joseph Wang and colleagues of the Department of Nanoengineering, University of California San Diego, actively monitors the production of warning signs an athlete or anyone performing intense physical activity, is coming to the end of their physical endurance, and is about to simply lock up, with their muscles physically unable to go any further.

Credit: American Chemical Society

The biosensor, which simply affixes to the skin like a temporary tattoo – peel and stick – works by analysing the content of the sweat extruded from the skin during exercise. Its' entire adhesive side is one big microfluidic laboratory.

The biosensor is checking for one compound in particular: Lactate.

Lactate is a form of lactic acid which is released in sweat when the muscles need more energy than the body can supply from aerobic respiration. Aerobic respiration is the normal oxygen-based means of supplying ATP to the muscles that happens all the time, except when the body is under intense pressure, such as in extreme or long-term athletics.

When aerobic respiration is not enough, the body shifts to an “anaerobic” metabolism which makes up for the difference, but has a disastrous side effect: the muscles produce lactic acid as a waste product. The specific form of lactic acid known as lactate builds up in the muscles, and in the body in general, the longer the anaerobic process goes on.

Eventually the lactate waste builds up beyond the muscle's ability to contain it, and the energy supply is throttled out, forcing the muscles to work without receiving their fuel. This causes extreme exhaustion, and the infamous 'hit the wall' effect, where the person just cannot go any further – their muscles have hit their physical limit and have nothing left to give.

However, because that same lactate is released into the bloodstream, it ends up in the sweat. As the lactate levels in the body climb, so do the levels released in the sweat. This is exactly what the biosensor is monitoring. It can tell how close the athlete is to 'hitting the wall' in real-time by monitoring these levels.

At the moment, this sensor is undergoing its first clinical trials, with ten athletes having volunteered to wear it whilst they train. Currently, there is no map of what levels of lactate in the sweat equate to dangerous territory for the muscles, and that is where these trials, plus additional research by Wang and team come in.


First human tests of new biosensor that warns when athletes are about to 'hit the wall'

Electrochemical Tattoo Biosensors for Real-Time Noninvasive Lactate Monitoring in Human Perspiration (paper)

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