How Monitoring Your Sweat Could Reveal The State Of Your Health

"Wow, you're really salty," says Stefan van der Fluit, glancing at the numbers on my screen. I could have told him that myself - after a sweaty 45-minute workout on the exercise bike, salt is already starting to form on my T-shirt. But van der Fluit knows exactly how salty I am. According to the data, I've sweated out 347 milligrams of sodium in 370 millilitres of water. Thats on the high end in terms of sodium loss, and I definitely need to replenish.

Van der Fluit is the co-founder of Flowbio, a London-based company that specializes in sweat analysis for athletes. During my workout, I wore a sensor called the S1 on my upper arm, which collects sweat in a small channel, measures its volume and sodium concentration, and sends the data to a smartphone app. The app then calculates my total sodium loss.

For an endurance athlete, this kind of information would be invaluable - potentially the difference between winning and losing. I'm not an athlete at that level, but van der Fluit certainly is. As a competitive cyclist, hes struggled with dehydration for years. But ever since he started using the sweat sensor, those issues have disappeared, and his performance has improved.