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