The GX Sweat Patch is a wearable technology designed for monitoring an athlete’s unique hydration needs during exercise. This single-use, non-invasive device measures two individualized metrics: the rate of fluid loss and the concentration of electrolytes in sweat. Its core purpose is to provide a personalized “sweat profile” based on data collected during a typical workout session. This system aims to inform a more precise and effective strategy for fluid and electrolyte replacement during and after future workouts.
The Science of Sweat Analysis
The patch uses advanced microfluidic technology—a system of tiny, enclosed channels—to collect and analyze a small sample of sweat directly from the skin. This flexible, thin-film device adheres to the forearm and captures sweat as it is secreted by the eccrine glands. The process happens passively, driven by the natural pressure of sweat excretion, without requiring any battery or electronic sensors in the patch itself.
The patch contains two distinct channels that use chemical reactions for measurement. One channel contains a non-toxic orange dye; the distance the colored fluid travels over the workout duration measures the local sweat rate. A second channel uses a specialized dye that changes color based on the concentration of chloride in the sweat. Since chloride is the primary negatively charged ion lost alongside sodium, this color change correlates directly to the athlete’s sweat electrolyte loss.
Proprietary algorithms within the companion application process these local measurements to extrapolate whole-body values. The system predicts the whole-body sweat rate and the total sweat sodium loss, metrics traditionally requiring cumbersome laboratory procedures like whole-body washdown. This method provides a convenient, field-ready assessment of the fluid and electrolyte composition of sweat, which is highly variable among individuals. Athletes can lose between 200 and over 2,000 milligrams of sodium per liter of sweat, highlighting the need for personalized analysis.
Applying and Using the GX Sweat Patch
To ensure the integrity and accuracy of the sweat sample, the user must clean the inner left forearm before beginning the workout. This area, approximately two to three inches below the elbow crease, must be free of oils, lotions, or moisture. This location is representative of the body’s overall sweat profile. The patch should then be firmly pressed onto the dry skin for several seconds to create a secure, watertight seal.
The patch is designed for a single workout session that is intense enough to generate significant sweat volume. A minimum wear time of about 20 minutes is required for sufficient sweat collection, though this may extend to 60 minutes for individuals with lower sweat rates. The maximum effective wear time before the microchannels become full is generally around 60 to 70 minutes, especially for heavy sweaters.
Immediately after the activity, the user must open the Gx App on a smartphone while the patch is still on the skin. The app uses the phone’s camera and image-recognition technology to capture and interpret the colored channels. This scan digitally transfers the raw data—the distance of the orange line and the intensity of the purple color—for analysis. This step finalizes data collection, allowing the app to generate the comprehensive sweat profile.
Interpreting Your Personalized Hydration Profile
The personalized hydration profile provides three main metrics: total sweat loss, sweat rate, and estimated total sodium loss. Understanding the sweat rate (the volume of fluid lost per hour) is fundamental for determining how much fluid to consume during future workouts to prevent significant dehydration. A fluid deficit of more than two percent of body mass can negatively affect cognitive and physical performance, making this metric an important guide for fluid planning.
The sweat sodium concentration is equally important, as it identifies “salty sweaters” who lose a higher-than-average amount of electrolytes. For those with high sodium loss, the app’s recommendations emphasize incorporating more sodium into their fluid replacement strategy to maintain proper fluid balance and muscle function. For example, two athletes may have the same sweat rate, but the one with a higher sodium concentration requires a much saltier drink to compensate for the greater electrolyte loss.
These metrics are translated into personalized fluid intake recommendations tailored for future exercise sessions under similar environmental and intensity conditions. The app suggests a precise volume of fluid to consume per hour and a target sodium content for that fluid. By adhering to these data-driven guidelines, athletes can proactively adjust their pre-workout nutrition and in-session fluid intake to optimize performance and accelerate post-exercise recovery.