{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,16]],"date-time":"2026-09-16T20:48:09Z","timestamp":1789591689191,"version":"build-2803163510"},"reference-count":49,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2026,4,21]],"date-time":"2026-04-21T00:00:00Z","timestamp":1776729600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Center of Excellence in Creative Engineering Design and Development (CED2), Thammasat University"},{"id":[{"id":"https:\/\/ror.org\/002yp7f20","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Global warming and increasing heatwaves elevate the risk of exertional heat illnesses, particularly heatstroke, in endurance athletes and outdoor workers. This study developed and validated a wearable heatstroke warning system integrating physiological and environmental monitoring with a real-time web dashboard. The wrist- and finger-worn prototype comprised an ESP32 microcontroller and heart rate (MAX30101), skin temperature (MAX30205), ambient temperature and humidity (SHT31), and galvanic skin response (Grove-GSR v1.2) sensors with dual acoustic\u2013visual alerts and WiFi transmission. Fifteen triathletes (18\u201339 years) completed 30 min of cycling in a climatic chamber: 0\u201315 min at 24 \u00b1 1 \u00b0C, 70 \u00b1 10% RH, and 16\u201330 min at 27 \u00b1 1 \u00b0C, 90 \u00b1 10% RH, with the workload rising from 40%HRmax by 10% every 10 min. Heart rate, estimated core temperature, ambient temperature, relative humidity, and GSR were recorded every 30 s and compared with standard devices using Spearman correlation (p = 0.01) and Wilcoxon signed-rank tests (p &lt; 0.05). Heart rate, skin temperature (used a linear model to calculate core body temperature), ambient temperature, and humidity sensors showed fair\u2013very good validity (r = 0.692, 0.995, 0.994, 0.952), while GSR was low (r = 0.298). No significant differences were observed for heart rate, skin temperature, and humidity (p &gt; 0.05), but body temperature (p = 0.003) and GSR (p &lt; 0.001) differed. The system showed promising validity for real-time heatstroke risk monitoring, with further refinement needed for skin temperature and GSR sensing.<\/jats:p>","DOI":"10.3390\/s26082556","type":"journal-article","created":{"date-parts":[[2026,4,21]],"date-time":"2026-04-21T11:42:45Z","timestamp":1776771765000},"page":"2556","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Development of Wearable Heatstroke Warning System (HeatGuard): Design, Validation and Controlled-Environment Testing Among Triathletes"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6461-9764","authenticated-orcid":false,"given":"Kanchana","family":"Silawarawet","sequence":"first","affiliation":[{"name":"Department of Electrical and Computer Engineering, Faculty of Engineering, Thammasat School of Engineering, Thammasat University, Pathum Thani 12121, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0005-3766-8172","authenticated-orcid":false,"given":"Chutipon","family":"Trirattananurak","sequence":"additional","affiliation":[{"name":"School of Information, Computer, and Communication Technology (ICT), Sirindhorn International Institute of Technology, Pathum Thani 12121, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0002-2729-8612","authenticated-orcid":false,"given":"Jirawat","family":"Muksuwan","sequence":"additional","affiliation":[{"name":"Department of Electrical and Computer Engineering, Faculty of Engineering, Thammasat School of Engineering, Thammasat University, Pathum Thani 12121, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0005-7147-9666","authenticated-orcid":false,"given":"Surasak","family":"Sangdao","sequence":"additional","affiliation":[{"name":"Department of Sports Science and Sports Development, Faculty of Allied Health Sciences, Thammasat University, Pathum Thani 12121, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-4193-1280","authenticated-orcid":false,"given":"Darawadee","family":"Panich","sequence":"additional","affiliation":[{"name":"Department of Medical Engineering, School of Engineering, Thammasat University, Pathum Thani 12121, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1697-4427","authenticated-orcid":false,"given":"Sairag","family":"Saadprai","sequence":"additional","affiliation":[{"name":"Department of Sports Science and Sports Development, Faculty of Allied Health Sciences, Thammasat University, Pathum Thani 12121, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,4,21]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1978","DOI":"10.1056\/NEJMra011089","article-title":"Heat stroke","volume":"346","author":"Bouchama","year":"2002","journal-title":"N. 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