(365b) A Wearable Fabric Sensor for Monitoring Hydration in High-Level Athletes

Currently, there is a need for more accurate and more convenient methods of sweat sodium testing for endurance athletes. Sweat sodium is known to have a notable correlation to body fluid balance, making it an ideal way to detect and monitor overall hydration status. However, traditional sweat sodium monitoring can be inaccurate as it requires sample collection and analysis to be performed in separate steps. This research focuses on a newly designed wearable fabric sensor (WFS). The sensor consists of a non-woven fabric base that is treated with dispersed carbon nanotubes. The carbon nanotubes on the fabric are then functionalized with a size selective molecule for sodium detection. After calibration and assembly, the WFS can be worn by the athlete during exercise. As sodium binds to the WFS, the change in resistance is measured and output via custom-made Bluetooth electronics. After the test, the athlete’s steady-state sodium loss, time to start sweating, and time to reach steady-state sodium loss are all determined. Because of its unique design, this WFS can jointly collect and analyze sweat samples during exercise and can improve the ease and accuracy of on body sweat analysis. During this study, subjects (n = 31, ages 18-60 years) wore a WFS during a 30-minute cycle ergometry test at about 65% heart rate reserve or 90-minute running test at moderate intensity. The participant’s sweat was collected every 15 minutes on the lower forearm using sweat collectors. Additionally, subjects wore the wearable fabric sensor (WFS) on the upper forearm throughout the duration of the test. The sweat collected was analyzed using a commercial sweat sodium analyzer (SSA). Comparisons were made between the measurements from the SSA and from the WFS. Accuracy was determined by comparing predicted WFS concentration to the actual concentration from the commercial SSA and analyzed statistically using ANOVA and Bland-Altman plots. Bland-Altman analysis of the cycling data showed the average concentration difference between the WFS and the SSA was 5.35 mM, with 99% of data points between +/- 1.96 times the standard deviation (SD). Additionally, Bland-Altman analysis of the running data showed an average concentration difference between the WFS and SSA of 0.83 mM, with 92% of data points between +/- 1.96 times the SD. For both the running and cycling trials, the WFS showed similar average sweat sodium values as compared to the SSA. These analyses show that there is no statistical significance between the values reported by the WFS and the SSA. In summary, the WFS accurately predicted sweat sodium concentration during endurance exercise when compared to an SSA.

This work was funded by NSF [grant number 1843539], Ohio Third Frontier TVSF [grant number 20-0004], and NSF [grant number 2111983]