Believe it or not, one of the most difficult elements of endurance training isn’t physical fitness, but figuring out when and how much to drink. For the most part, athletes such as runners, cyclists, and triathletes use simple trial and error to figure out how much water and electrolytes they need to fuel their workouts. Because despite all the fancy fitness-tracking tech available, there’s no better way to tweak your hydration strategy—until now.
Similar to a fitness or sleep tracker, the new Nix Hydration Biosensor analyzes your sweat in real time, leading the company to dub it a “portable hydration lab.” It comes with a sensor and four stick-on patches designed to send mid-workout reminders based on how much fluid you’ve lost, and process your sweat data post-workout to suggest the right electrolyte mix for future workouts.
If you’re questioning why someone might need so much information, consider the following: According to a report published in Frontiers in Physiology; At the same time, electrolytes are essential for muscle contraction and can also play a role in preventing muscle fatigue. The longer you exercise (and the more intense the conditions under which you exercise), the more important it is to make sure you’re getting enough of both.
As someone who routinely runs two hours or more and has total meltdowns during marathons due to poor hydration choices, I appreciated the opportunity to test out Nix’s new biosensor. Here’s what I’ve learned while wearing it on both indoor and outdoor runs.
Using an adhesive sensor and an easy-to-read mobile app, the Nix Hydration Biosensor not only analyzes your sweat while exercising, it also suggests a personal hydration strategy to keep you going longer while preventing muscle fatigue. Ideal product for anyone training for long distance races, triathlons or marathons.
Before your workout, you put a patch on your bicep (the perfect area for a sweat test) and turn on the sensors. Then, when you start a workout in the Nix app, you can choose your parameters — like run/cycling, indoor/outdoor — and whether you want fluid loss and/or electrolyte loss notifications. I opted to be notified every time I lose an ounce of fluid (but you can also opt for time-based notifications). During my 35-minute treadmill run, I keep the app open on my phone to see what happens.
I started sweating noticeably around 8 minutes and wiped sweat off my face at 17 minutes, but the app didn’t register any sweat loss until 21 minutes (the app did warn that it could take up to 25 minutes Display Data). Afterwards, I could see my loss in real time; after about 25 minutes, my fluid loss decreased from 0.6 oz and 27.5 mg of electrolyte loss to 1.3 oz and 55.1 mg of electrolyte loss. You don’t need to leave the app open, though; I programmed it to send an alert to my Apple Watch during my 10-mile outdoor run.
After you’ve finished your workout, the app uses the data it collects to determine your sweat composition, or how many milligrams of electrolytes you’ve lost per ounce of fluid. During my short indoor runs, I was at 44 mg per ounce. In a longer outdoor run (37°F, 57% humidity; the sensor recorded this data), it was 25 mg per ounce.
With each workout recap, the app includes a graph showing which hydration drink matches your sweat composition best under those conditions: My indoor runs corresponded to Liquid IV, and my outdoor runs corresponded to Nuun. My takeaway: During long outdoor workouts in similar temperatures, I should aim to drink 13.8 ounces of water per hour with Nuun tablets in it.
The first time I used the Nix sensor was during a 1 hour 20 minute long run outside; the temperature was 33°F and the humidity was 41%. I definitely sweated — when you’re doing cardio for over an hour, it’s hard not to sweat, even in near-freezing temperatures — and yet, the sensor didn’t pick up any sweat data. When I contacted the company, they said it was unusual, but they do see it happen from time to time, especially in the lower temperature range. It can also cause problems if your body surface temperature drops during your run (i.e. your pace changes or you stop). I did try again and got results on a different outdoor, but I was pissed off wasting the whole patch.
While the Nix sensor is reusable, the patch is disposable. When you’re done with all four sweat patches, you can buy a pack of four refills for $25, which makes sense because once the sweat hits the receptors on the patch, they won’t be able to register accurately in the future data. But it also guarantees more purchases in the future, which obviously adds up over time (especially if you don’t get a reading during your workout).
As cool as this technology is, it’s probably not something the average fitness enthusiast needs to invest in. But if you’re doing endurance training — whether it’s for a marathon, bike race, triathlon, etc. — If you’re looking to optimize your hydration for better performance, this little patch takes some of the guesswork out of how much water and electrolytes you need during exercise.
It may not be something you will wear to every workout, but if you use it strategically (i.e. on long runs in marathon training, or in conditions that mimic what you would expect on race day), you will Know what you need to perform at your best on race day.