All-in-One, Wireless, Multi-Sensor Integrated Athlete Health Monitor for Real-Time Continuous Detection of Dehydration and Physiological Stress

Abstract

Athletes are at high risk of dehydration, fatigue, and cardiac disorders due to extreme performance in often harsh environments. Despite advancements in sports training protocols, there is an urgent need for a non-invasive system capable of comprehensive health monitoring. Although a few existing wearables measure athlete's performance, they are limited by a single function, rigidity, bulkiness, and required straps and adhesives. Here, an all-in-one, multi-sensor integrated wearable system utilizing a set of nanomembrane soft sensors and electronics, enabling wireless, real-time, continuous monitoring of saliva osmolality, skin temperature, and heart functions is introduced. This system, using a soft patch and a sensor-integrated mouthguard, provides comprehensive monitoring of an athlete's hydration and physiological stress levels. A validation study in detecting real-time physiological levels shows the device's performance in capturing moments (400-500 s) of synchronized acute elevation in dehydration (350%) and physiological strain (175%) during field training sessions. Demonstration with a few human subjects highlights the system's capability to detect early signs of health abnormality, thus improving the healthcare of sports athletes.

Keywords: all‐in‐one wearable; athlete health monitor; chest patch; dehydration detection; physiological stress; smart mouthguard.

Figure 1

Overview of an all‐in‐one wearable system for athlete health monitoring. A) Illustration depicting a wearable smart mouthguard and chest patch for continuous dehydration assessment and health monitoring through saliva and cardiovascular signal analysis. B) Detailed illustration of a smart mouthguard. C) Detailed illustration of a chest‐wearable soft patch. D) Flow chart describing the aim of combinatory monitoring strategies for a dehydration warning scheme using physiological strain and saliva osmolality.

Figure 2

Fabrication and characterization of smart mouthguards and soft chest patches. A) Front and backside view of a mouthguard with integrated, flexible PCB and rechargeable battery on lip guard, micro‐gap electrode on the inner side wall. B) Fabrication of an electrode using a heat‐responsive adherent polyimide film to cover a conductive foil layer. C) Microscopic images of micro‐gap electrodes showing a circular gold surface with 100 µm gap. D) Electrical impedance spectroscopy data from the electrode in standard calibrator, demonstrating linear impedance proportional to osmolar levels. E) Front and backside view of a soft chest patch. F) Fabricated nanomembrane electrodes on the adherent substrate. G) Microscopic images of the serpentine gold electrode. H) Peeling test results illustrating adhesion strain according to different substrates and loading.

Figure 3

Validation of the smart mouthguard's performance. A) Device calibration with standard osmolar samples ranging from 29 to 232 mOsm. B) Results showing stable signals from the micro‐gap electrode immersed in artificial saliva at 100 mOsm. C) Demonstration of continuous osmolar change detection using 29, 87, 174, 232, 174, 87, and 29 mOsm sequentially. D) Comparison of calibration data between a commercial saliva osmometer (MX3), a gold standard precision system (Micro‐Osmette osmometer), and a smart mouthguard developed in this work.

Figure 4

Validation of bioelectric signals from the soft chest patch. A) Schematic illustration showing device mounting locations (left) and a photo of a test subject wearing devices for an indoor treadmill test (right). B) Comparison data of heart rates between the soft chest patch and the commercial device (Polarbeat). C) Motion tracking data and specific movement charts; the top graphs show short‐term recorded accelerometer data for each activity, the middle photos show the test setup for continuous data monitoring using tablets, and the bottom graph displays a complete data set including all motions. D) Flowchart detailing data acquisition and processing using a mouthguard device and a chest patch.

Figure 5

Experimental results of measured saliva osmolality and cardiovascular data from an hour‐long treadmill running test. A) Series of photos showing chest patch wear, saliva osmolality testing with a commercial device, and subject running on the treadmill. B) Magnified set of recorded ECG. C) Recorded ECG (top) and calculated HR from the ECG data (bottom). Each session timeline is depicted on the graph. D) Collective data of LnRMSSD HRV, HR, and P‐PSI. E) Comparison of measured saliva osmolality between a smart mouthguard showing continuous data measurement and a commercial device showing a discrete data detection (MX3). F) Collective set of continuously measured data including saliva osmolality, HR, temperature, and P‐PSI. The black box indicates the detected moment of the highest saliva osmolality peaks from the wearable devices.

Figure 6

Field test during a football players' training session. A) Photo of a football player wearing a smart mouthguard and a soft chest patch. B) Flow chart showing backup storage implementation in the system. The measured data can be automatically recorded to the microSD when Bluetooth connection between devices occurs. C) Collective graph displaying recorded saliva osmolality, HR, P‐PSI, and LnRMSSD HRV.