This Sticker-Like Patch Can Help You Optimize Your Workout Hydration

Talk to any trainer or sports nutritionist and they'll mention a few times the power of fueling properly for your workouts. In order to give a workout your all or even just to feel energized enough for a stroll around the block, you need a nutrition plan that keeps your body running strong — and that includes water and electrolytes. (

But how do you know how much water and electrolytes to take in? Going off thirst alone can only take you so far. Enter the Gatorade Gx Sweat Patch (Buy It, $25 gatorade.com,), which features a corresponding app to help you pinpoint exactly how much water you need to replenish the fluids lost during a training session. The patch and app can also share how much sodium you lost during a workout via sweat, so you'll know whether you need additional electrolytes. Sodium may have a bad rap, but it's actually an important electrolyte that helps you maintain balanced hydration levels.

How the Gatorade Gx Sweat Patch Works

The patch itself feels much like a sticker, and the brand suggests placing it on the inside of your left forearm for best results. When you start to sweat, you'll see a line on the patch start to turn orange — the more you sweat, the more you'll see that line grow toward the bottom of the patch. There's also an area on the side of the patch that analyzes your sweat for sodium concentration, which helps tell you how much sodium you lost. When you're done with the workout, you scan the patch using the app (similar to scanning a QR code), the technology will analyze the results and deliver your sweat rate (how much sweat or fluid you lose per hour of exercise) and sodium loss (how much sodium within that fluid you lost during your workout).

"The patch can be helpful for endurance athletes to measure their sweat rate and amount of sodium found in their sweat to develop a hydration plan when training or racing events longer than an hour," says Megan Robinson, R.D., sports dietitian and RRCA-certified run coach. "If you're an athlete that struggles with finding the right hydration plan or is a heavy sweater, this information can help guide you in the right direction to prevent dehydration or over-hydration so you can perform [at] your best," says Robinson.

Researchers with the Gatorade Sports Science Institute have been testing athletes' hydration levels for more than three decades, but they wanted to evolve the process into something the everyday athlete could have access to in real-time. Before, athletes would wear a patch similar to the one now sold to consumers, but it would still take time for the scientists to analyze their sweat and give them personalized recommendations, explains Matt Pahnke, Ph.D., senior principal scientist at the Gatorade Sports Science Institute. Now, everyday athletes can feel more in control of their hydration and overall training performance.

Simply having general recommendations around hydration intake for everyone doesn't cut it because there's a wide range of how much fluid and electrolytes can be lost through exercise, explains Pahnke. "Some athletes lose less than 14 ounces an hour; some athletes lose over 84 ounces an hour," which illustrates just how much hydration needs and fluid loss (two key factors in performance and recovery) can vary from person to person.

In addition to telling you how much sweat you lose and how much you should drink up to replenish, the Gx Sweat Patch also reads what's actually in that sweat — mainly focusing on sodium. "The reason that you get sodium numbers reported back to you is we know that sodium is really the key electrolyte that you lose in your sweat," explains Pahnke. Fluid moves in and out of your cells as you sweat and sip water, and sodium provides the key to balancing that liquid loss and gain, he adds.

Why You Should Care About Your Sweat Rate and Sodium Loss

If you're running or biking or even going for a long walk in hot and humid conditions, you may lose even more sweat and sodium, and this can impact your hydration, as well as performance, which is why it's helpful to test the Gx Sweat Patch in a few different environments to determine your fluid and sodium needs in those conditions, according to Pahnke.

"Your goal is to lose no more than 2 percent of your body weight in sweat," says Robinson."Once you lose more than that, this can increase your heart rate, decrease blood volume, and overall impact your training and/or racing performance." That's why figuring out how much water you need to replenish the fluids you lost is so important.

If the Gatorade patch tells you that you lose 900 mL of sweat per hour, for example, that might translate into drinking a recommended 225 mL of water every 15 minutes during your training session, explains Robinson.

Similarly, knowing how much sodium you lose during a workout can help you determine how many electrolytes you need to keep your body moving at optimal capacity. "Sodium losses can vary greatly depending on if you are a salty sweater and/or if you consumed a meal high in sodium right before training," says Robinson. "It is assumed that most endurance athletes can lose up to 500-1000 mg sodium per hour, but you don't want to assume that you need to consume an electrolyte beverage containing that amount each hour." Having something like the Gx Sweat Patch determine how much sodium you lose can give you a more personalized idea of how much sodium to take in during your workout. (More: Can Drinking Water Actually Help You Lose Weight?)

Putting the Gatorade Gx Sweat Patch to the Test

At Pahnke's suggestion, I tested the Sweat Patch in a few different environments, from a hot, humid 90-degree run outdoors to a more moderate-intensity weightlifting session indoors. The patch itself is easy to use — simply place the patch on clean, dry skin on your inner forearm. You'll begin to notice the oddly satisfying orange-filled line on the patch appear as you sweat. Continue your workout like normal, then after you're done, the Gatorade Gx app analyzes your sweat and provides a "sweat profile" — the more times you do this, the better the app will understand your fluid and sodium needs tailored to specific workouts.

I found a few surprising bits of info from my results: I'm ranked "low" in sodium loss, which means I don't actually lose that much sodium in my sweat (even during that hot, humid run). That also means I don't need a high amount of electrolytes (namely, sodium) from sports drinks or an endurance gel when I'm out for a run.The hydration tips in the app were super doable, as well — drinking just 7 ounces of fluid before a shorter run or strength session for example felt achievable.

You get out of the Gx Sweat Patch what you put into it, explains Pahnke. To really maximize the recommendations, you need to manually enter a decent amount of info into the app. For your workouts, you'll answer questions about intensity level, the environment, and whether you drank anything throughout the bout of exercise. You'll also answer surveys about fatigue levels. (More: Chronic Fatigue Syndrome Is More Than Just Being Really Tired All the Time)

Also, if you want recommendations on how much to drink or eat before a workout, you actually have to schedule the workout in the app. That way, it'll tell you when and how much to consume water, protein, carbs, or caffeine. Then, recording what you actually consume requires manual entry, too. But the more info you give the app, the better the recommendations.

A few downfalls of the patch include that it doesn't always stick well to the skin, and I found that my app sometimes had trouble scanning the patch. Also, to get a full picture of your fluid and sodium requirements, it's best to test the patch multiple times in multiple environments. You only get two patches with your purchase (and the patch is single-use), so you'd need to stock up to get a more accurate account of your hydration needs. (

Who Gatorade Gx Sweat Patch Is Best for

It's smart to use the Sweat Patch is if you're training for a long endurance event and need some recommendations on fueling properly, particularly your water and sodium intake. Or if you're chasing a PR and need all the insights you can get to take your performance to the next level. If those are your goals, use a patch throughout your training cycle as your body adjusts to the load and the weather changes, suggests Pahnke. That means testing your sweat at the beginning of training, toward the middle, and then again close to race day. "As you build more sweat profiles — in the cooler weather and hot weather — it's going to get smarter the more times you use it, and the better information you'll get," says Pahnke.

Does everyone need to test their sweat? Probably not, says Pahnke. If you typically work out for 20 minutes at a time, you likely don't need to test your fluid or sodium loss. It's those longer efforts that require rehydrating and refueling and the Gatorade Gx Sweat Patch and app can help you do it the right way.