The Dynamic Response of Sweat Chloride to Changes in Exercise Load Measured by a Wearable Sweat Sensor

Dong-Hoon Choi,Grant B Kitchen,Peter C Searson,Kerry J Stewart

doi:10.1038/s41598-020-64406-5

Dong-Hoon Choi, Grant B Kitchen + Show 2 more

Open Access

https://doi.org/10.1038/s41598-020-64406-5

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Abstract

Wearable sensors enable the monitoring of an individual’s sweat composition in real time. In this work, we recorded real-time sweat chloride concentration for 12 healthy subjects in three different protocols involving step changes in exercise load and compared the results to laboratory-based analysis. The sensor results reflected the changes in exercise load in real time. On increasing the exercise load from 100 W to 200 W the sweat chloride concentration increased from 12.0 ± 5.9 to 31.4 ± 16 mM (mean ± SD). On decreasing the load from 200 W to 100 W, the sweat chloride concentration decreased from 27.7 ± 10.5 to 14.8 ± 8.1 mM. The half-time associated with the change in sweat chloride, defined as the time at which the concentration reached half of the overall change, was about 6 minutes. While the changes in sweat chloride were statistically significant, there was no correlation with changes in sweat rate or other physiological parameters, which we attribute to intra-individual variation (SD = 1.6–8.1 mM). The response to exercise-induced sweating was significantly different to chemically-induced sweating where the sweat chloride concentration was almost independent of sweat rate. We speculate that this difference is related to changes in the open probability of the CFTR channel during exercise, resulting in a decrease in reabsorption efficiency at higher sweat rates.

Highlights

Electrolytes regulate fluid balance in plasma and tissues and are involved in cell signaling[16], and electrolyte imbalance can lead to a wide range of medical conditions[17,18]
We show that the response to exercise-induced sweating and chemically-induced sweating are significantly different, values obtained at an exercise intensity below 100 W exercise load are comparable to results from chemically-induced sweating
Sweat profiles measured using a wearable sensor. 12 healthy subjects were asked to spin on a stationary bike following three different protocols following a warm up: (1) a single step trial: 100 W (20 minutes) to 200 W (20 minutes), (2) a reverse step trial: 200 W (20 minutes) to 100 W (10 minutes), and (3) a multi-step trial: 100 W–200 W in 25 W increments for 10 minutes each

Summary

Introduction

Electrolytes regulate fluid balance in plasma and tissues and are involved in cell signaling[16], and electrolyte imbalance can lead to a wide range of medical conditions[17,18]. To assess the feasibility of using a wearable sensor to evaluate transient changes in real-time, we performed a systematic study of the dynamic response of sweat chloride to step changes in exercise load. We performed trials with 12 healthy subjects while spinning on a stationary bike using three different protocols involving step changes in power output from 100 W to 200 W, 200 W to 100 W, and 100 W to 200 W in 25 W increments. We show that the changes in sweat chloride (∆C) on changing exercise load were statistically significant, there was no correlation between ∆C and sweat rate or other physiological parameters, which we attribute to intra-individual variation. We show that the response to exercise-induced sweating and chemically-induced sweating are significantly different, values obtained at an exercise intensity below 100 W exercise load are comparable to results from chemically-induced sweating

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