Circadian Timing and Heat Stress in Firefighters

Title & Dataset supporting: Circadian modulation of core temperature and thermoregulatory strain during live-fire compartment exposure in firefighters Mauvieux B., Markov A., Besnard S., Touitou Y., Edwards B.J. (2025) Description : This dataset accompanies the manuscript submitted to the Journal of Thermal Biology. It contains anonymized physiological and environmental data recorded during standardized live-fire compartment training conducted at two circadian phases: late morning (09:00 h) and late evening (21:30 h). Twenty-one male professional firefighters completed both sessions on the same day under matched thermal loads. The dataset allows replication of all analyses described in the paper, including core-temperature kinetics, cardiovascular and perceptual strain, hydration indices, and environmental thermal gradients. Data content - The repository includes the following files: Tcore_AM_PM.csv (Continuous core temperature (°C) recorded via ingestible e-Celsius® sensors) Variables: Subject_ID, Condition (AM/PM), Time_min, Tcore_C. HR_RPE_BW.csv Heart-rate data, Borg RPE, body mass and total body water pre/post exposure. Variables: Subject_ID, Condition, HR_mean, HR_max, RPE, BodyMass_pre, BodyMass_post, TBW_pre, TBW_post. Skin_Microclimate.csv Chest and neck skin temperature (°C) and under-PPE humidity (%RH). Variables: Subject_ID, Condition, Tskin_chest, Tskin_neck, Temp_underPPE, RH_underPPE. Environment_Thermocouples.csv Air-temperature recordings (°C) from vertical thermocouple trees at five heights (0.10–2.30 m). Variables: Session_ID, Condition, Height_m, Time_min, Temp_C. Summary_Table1.xlsx Summary statistics (mean ± SD) for all physiological variables, matching Table 1 of the manuscript. Metadata_StudyDesign.pdf Overview of study design, measurement devices, calibration details, and analysis workflow (R v4.x; lme4, afex, emmeans). Units All temperatures are in degrees Celsius (°C). Heart rate: beats per minute (bpm). Body mass: kilograms (kg). Total body water: percentage of body mass (%). Humidity: relative humidity (%RH). Time: minutes relative to exposure start (T = 0 min). Ethics and confidentiality : All participants provided written informed consent. Data are pseudonymized (Subject IDs = random numeric codes) and comply with the GDPR MR-004 framework (CNIL, France). Licensing : This dataset is released under the Creative Commons Attribution 4.0 International (CC BY 4.0) licence, permitting reuse with proper citation. Citation - If you use these data, please cite: Mauvieux B., Markov A., Besnard S., Touitou Y., Edwards B.J. (2025). Circadian modulation of core temperature and thermoregulatory strain during live-fire compartment exposure in firefighters. Dataset available at Mendeley Data . Contact For questions or additional data access, please contact: Benoit Mauvieux – Normandie Univ., UNICAEN, UR 7480 VERTEX, Caen, France Email: [e-mail] ORCID: 0000-0003-4862-6531