Fig. 3
From: Wearable sensors for monitoring the physiological and biochemical profile of the athlete
Monitoring the mental acuity of the athlete via measurement of heart rate variability, skin conductivity (galvanic skin response), or biomarkers from eccrine sweat. a Schematic illustrating the derivation of heart rate variability from an ECG. The ECG presented herein is depicting respiratory sinus arrhythmia. Heart rate increases thus decreasing the time between successive RR intervals during inhalation and exhalation. The change in time between successive RR intervals is called heart rate variability, expressed in ms. Short heart rate variability is indicative of high-stress levels whereas long heart rate variability is indicative of a calm period. b Human stress monitoring patch affixed to a human wrist (c) Performance of the pulsewave sensor from panel (b) for varying differential pressure of heart beat depending on the heart rate of 50 BPM, 145 BPM, and 220 BPM as a function of the change in time. d Performance of the pulsewave sensor from panel (b) for varying differential pressure of heart beat depending on the heart rate of 50 BPM, 145 BPM, and 220 BPM as a function of output voltage. e Image of an epidermal sensor applied to the forearm of a healthy volunteer to detect cortisol levels from eccrine sweat. f Real-time response of the molecularly selective and control devices after completion of physical exercise. The cortisol response was recorded using the output measurement and the data were represented as a change of drain current vs. time at a low voltage. g The data demonstrated a good correlation with standard cortisol ELISA methods for cortisol detection with an RSD of 5% for the two measurements. Figures were reproduced with permission from Firstbeat Technologies80 (a), Yoon et al.74 (b–d), and Parlak et al.111 (e-g)
