Annals of Human Biology · Published 2026-07-30 · DOI 10.1080/03014460.2026.2705279
Hiroki Mani, Fumitsugu Io, Keiichi Ohba, Yasuhiro Sonoda
Background Occupational heat exposure is a growing public health concern in Japan, where hot, humid summers contribute to heat-related illnesses (HRIs).Aim To characterise the thermophysiological responses of Japanese outdoor workers to summer heat exposure and explore the effect of a practical pre-cooling approach.Subjects and methods Two field-based experiments were conducted in August-September. In Experiment 1, heart rate (HR) and core body temperature (CT) were continuously monitored under routine working conditions. In Experiment 2, workers performed their duties after pre-work ingestion of a 100 g carbohydrate–electrolyte ice slurry. HR and CT were assessed using non-invasive wearable sensors, and subjective thermal perception was recorded during the workday.Results Under high environmental heat stress (maximum Wet Bulb Globe Temperature: 30.2 ± 2.4 °C and 29.4 ± 2.1 °C), both CT and HR increased significantly during midday and afternoon periods. No significant differences were observed between the conditions in terms of HR, CT, or subjective thermal perception.Conclusion Japanese outdoor workers exhibited a sustained elevation in thermophysiological strain during summer. A low-volume pre-cooling strategy did not measurably modify these responses, indicating a limited physiological impact under real-world conditions.
Abstract from DOAJ. Public domain (CC0 1.0).
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Mani, H., Io, F., Ohba, K., et al. (2026). Limited efficacy of low-volume ice slurry ingestion on physiological heat strain in Japanese outdoor workers during summer. Annals of Human Biology. https://doi.org/10.1080/03014460.2026.2705279