Objectives: We developed a wearable sensor for the real time measurement of sweat rate in localized areas of the human body. This sensor represents the first step in the development of a wearable sensor network capable to estimate the global sweat rate via an ad hoc algorithm. Such device would be used to monitor athletes` hydration status during training and improve their performances. Equipment and methods: For this study, we tested our sensor on thirteen football players during a cycling test on a cycle ergometer. The sweat rate sensor was compared to a medical device that, although measuring a different physiological process, provides discrete data based on the same working principle, i.e. the diffusion of the water vapour emitted from the skin. Results: Our sensor has a working range up to 400g/m2·h. The statistical analysis and the Bland-Altman plot proved that our sensor is comparable to the medical device used as gold standard. At low sweat rate, the bias is 3.4g/m2·h with a standard deviation of 7.6g/m2·h. At maximum sweat rates, the bias is 2.3g/m2·h with a standard deviation 6.9g/m2·h. The P-values for the Bland-Altman plots at low and maximum sweat rate (0.1331 and 0.2477 obtained by Kolmogorov-Smirnov test, respectively) allow the hypothesis that there is a significant difference between our sweat rate sensor and the medical device to be rejected. Conclusion: We presented a prototype of a wearable sweat rate sensor for localized measurements. The trials on thirteen athletes proved that the performance of our sensor is comparable to that of a commercial medical device. This sweat rate sensor can provide valuable information on athletes` hydration status.
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