Defining Sex- and Age-Specific Initial Stay Times for Continuous Heavy-Intensity Work in Hot Environments Before...

Area of Science:

• Occupational health and safety
• Environmental physiology
• Heat stress research

Background:

• Industry guidelines recommend work-rest schedules to prevent heat-related illness.
• Current guidelines for initial work durations (IST) are based on moderate-intensity work.
• Data on IST during heavy-intensity work are limited.

Purpose of the Study:

• To determine if sex and age influence initial work durations (IST) during heavy-intensity work.
• To assess core temperature elevations in different demographic groups under heat stress.
• To inform updated occupational heat stress guidelines.

Main Methods:

• Simulated heavy-intensity work in controlled environmental conditions (26°C, 29°C, 32°C WBGT).
• Monitored work durations until core temperature exceeded 38.0°C or increased by 1.0°C from baseline.
• Included young (18-30 years) and older (50-69 years) males and females.

Main Results:

• Higher WBGT temperatures significantly increased the likelihood of reaching unsafe core temperatures.
• Median durations to reach 38.0°C decreased as WBGT increased.
• Older females showed a higher likelihood of reaching unsafe core temperatures compared to young males.

Conclusions:

• Older females are at increased risk during heavy-intensity occupational heat stress.
• Current IST guidelines may not adequately protect all worker demographics.
• Tailored heat stress management strategies are necessary for vulnerable populations.