Marathoners and others who engage in intense exercise often describe "hitting the wall" — when the body feels like it's shutting down after a period of prolonged exertion — as a key challenge to push past to complete a competition.  But scientists have developed a new sensor that can alert athletes when they’re about to hit that wall.

 

The device, which is applied to the skin like a temporary tattoo, can help "extreme" athletes monitor their stamina and fitness and help them prepare for that "wall" by tracking a form of lactic acid, released in sweat when the body is highly stressed.

 

In a new report published in the American Chemical Society journal Analytical Chemistry, the sensor's developers say describe the first human tests of the device and say that it could help soldiers and others who engage in intense exercise — and their trainers — keep tabs on their bodies' endurance.
 

"Such skin-worn metabolite biosensors could lead to useful insights into physical performance and overall physiological status, hence offering considerable promise for diverse sport, military, and biomedical applications," said the sports scientists.
 

Joseph Wang and colleagues explained that the sensor monitors lactate, which forms when muscles need more energy than the body can supply from the "aerobic" respiration that suffices during mild exercise. At such times, the body shifts to "anaerobic" metabolism, producing lactic acid and lactate. That helps for a while, but lactate builds up in the body, causing extreme fatigue and the infamous "wall," where an athlete feels that he or she cannot continue.
 

Existing methods of measuring lactate require blood samples or do not give instant results. But tests of the new lactate sensor on 10 volunteers showed that it accurately measures lactate levels in sweat during exercise, is easily applied to the skin like a temporary tattoo, and stays on and flexes with body movements.
 

The research was funded, in part, by the National Science Foundation and the National Institutes of Health.