Soon You'll Be Able to Tell What's Going On Inside Your Body While You Work Out

No more staring at the droplets on your sternum after a rigorous workout and whispering, "My children. If only you could speak."  I don't actually do that. That would be weird, especially in public. But I am a bit of a competitive FitBitter and like the idea of knowing how my body is doing during a workout. Researchers at Northwestern University have developed a first-of-its-kind microfluidic device that easily adheres to the skin and analyzes biomarkers in sweat to show how the wearer's body is responding to exercise.

The device, which is being called a "lab on the skin," measures total sweat loss along with four specific biomarkers: pH, lactate, chloride, and glucose concentrations, to tell you things like whether you need to drink more water or replenish electrolytes. As chloride ions are a biomarker for various diseases, researchers are also working toward using it to diagnose cystic fibrosis and other conditions.

A little larger than a quarter, the device will be inexpensive and designed for one-time use of a few hours, placed directly on the skin of the forearm or back. After your sweat is collected, your smartphone camera and an app read and analyze the results.

"Sweat is a rich chemical broth containing a number of important compounds with physiological health information," says lead researcher John A. Rogers, professor of materials science and engineering, biomedical engineering and neurological surgery at Northwestern University. "The sweat analysis platform we developed will allow people to monitor their health on the spot without the need for a blood sampling and with integrated electronics that do not require a battery but still enable wireless connection to a smartphone."

One practical application would be for marathoners and other endurance athletes to preemptively avoid "hitting the wall," or "the bonk," as we call sudden fatigue caused by a depletion of glycogen stores. Based on my personal experience, the bonk is a bitch.

Until now the standard for this sort of measurement has been sponges, pads, or fabrics, taped to the skin and analyzed in a lab. The device, according to a research report from Northwestern, was tested for accuracy and durability on two different groups of athletes: one cycling indoors in a fitness center and the other participating in the El Tour de Tucson, a long-distance bicycle race.

It will be another year or two before the "lab on the skin" goes to market.