Cooling Strategies for Heat Stress
Trial Summary
What is the purpose of this trial?
Occupational heat stress directly threatens workers' ability to live healthy and productive lives. Heat exposed workers are at an elevated risk of experiencing impaired work performance and cognitive function leading to a greater risk of work-related injuries which includes traumatic injury and a myriad of pathophysiological conditions (e.g., heat stroke, acute kidney injury, adverse cardiovascular events). To mitigate the adverse health effects of occupational heat stress, safety organizations recommend upper limits for heat stress, typically defined by a worker's metabolic rate and the prevailing wet-bulb globe temperature (WBGT). In instances where the heat load created by the combination of work intensity, environment, and clothing worn exceed the upper heat stress limits (uncompensable heat stress), controls such as rest breaks are prescribed to limit increases in core temperature beyond recommended limits. While workers are encouraged to find shelter from the heat during a rest break, it is not always possible or feasible. Typically, workers may rest while remaining exposed to the heat, recover in a shaded area or rest in an air-conditioned room or vehicle. However, the effectiveness of these cooling strategies in mitigating the level of physiological strain experienced by the worker during prolonged work in a hot environment remains unclear. In this project, the investigators will assess the efficacy of the different cooling strategies in preventing excursions in core temperature beyond recommended limits (38.0°C) following the initial stay time for moderate-intensity work in hot ambient conditions (WBGT of 29°C; represents hot outdoor conditions experienced by workers in summers in Ontario, Canada) in context of the prescribed American Conference of Governmental Industrial Hygienists (ACGIH) work-to-rest allocation for unacclimated adults. On three separate days, participants will walk on a treadmill at a fixed metabolic rate of 200 W/m2 until core temperature reaches and/or exceeds 38.0°C or until volitional fatigue. Thereafter, participants will complete an additional 180 min work bout employing the recommended ACGIH work-to-rest allocation of 1:3 (starting with a 45 min rest break followed by a 15 min work bout, with the cycle repeated three times over the 180 min work simulation bout) without (Control) or with cooling mitigation during each 15-min break consisting of either: i) partial cooling equivalent to sitting in a shaded space (WBGT 24°C; 31.7°C and 35% RH) such as under a tree with a light breeze (simulated with pedestal fan fixed at \~2 m/s) or ii) full cooling equivalent to sitting in air-conditioned space (e.g., room or vehicle) maintained at 22°C and 35% RH (equivalent WBGT of 16°C).
Will I have to stop taking my current medications?
The trial requires that participants do not use medications that significantly affect body temperature regulation and heat tolerance, such as antidepressants, antihistamines, and diuretics. If you are taking these types of medications, you may need to stop them to participate.
What data supports the effectiveness of the treatment for cooling strategies during heat stress?
Research shows that cooling strategies, such as using fans or cooling vests, can help reduce heat stress by lowering body temperature, heart rate, and sweat production during work in hot environments. Continuous cooling methods, like using conditioned air during work and rest periods, have been found to be more effective than intermittent cooling, improving comfort and extending work times.12345
Is cooling during work in hot environments safe for humans?
The research does not provide specific safety data for cooling strategies during work in hot environments, but it emphasizes the importance of managing heat stress to prevent health issues. Effective heat stress management, including cooling strategies, is considered crucial for worker safety and health.36789
How does the treatment of cooling strategies during rest breaks for heat stress differ from other treatments?
This treatment is unique because it involves using cooling strategies, like fans, during rest breaks to reduce heat stress, which is not commonly addressed by other treatments. It focuses on practical, immediate cooling methods during work breaks, unlike other strategies that may not provide direct cooling relief.1391011
Research Team
Eligibility Criteria
This trial is for healthy adults who can safely perform moderate-intensity work in hot conditions. Participants should be able to tolerate heat and engage in simulated work tasks on a treadmill. Those with medical conditions that could be worsened by heat, or who cannot follow the study's procedures, are not eligible.Inclusion Criteria
Exclusion Criteria
Trial Timeline
Screening
Participants are screened for eligibility to participate in the trial
Initial Stay Time
Participants perform continuous work until core temperature reaches 38.0°C or until volitional fatigue
Work-Rest Allocations
Participants complete a 180-minute work bout with a 1:3 work-to-rest allocation, with or without cooling strategies
Follow-up
Participants are monitored for physiological responses and safety after the work-rest allocations
Treatment Details
Interventions
- Simulated work in the heat with full cooling during rest breaks (Behavioural Intervention)
- Simulated work in the heat with no cooling during rest breaks (Behavioural Intervention)
- Simulated work in the heat with partial cooling during rest breaks (Behavioural Intervention)
Find a Clinic Near You
Who Is Running the Clinical Trial?
University of Ottawa
Lead Sponsor