Safe Maximum Work Times and the Effectiveness of Work-rest Allocations in Mitigating Increases in Core Temperature During and on the Day Following Prolonged Heavy-Intensity Work in the Heat in Young and Older Workers
试验速览
- 阶段
- 不适用
- 状态
- 已完成
- 入组人数
- 21
- 试验地点
- 1
- 主要终点
- Average core temperature
研究概览
简要总结
Workplaces rely on upper heat stress limits provided by the American Conference of Governmental Industrial Hygienists (ACGIH) to manage the health and safety of workers in hot environments. This is primarily achieved by interspersing work with rest periods, the length of which is dictated by environmental conditions and work intensity, to maintain core temperature at or below 38.0°C (equivalent to a 1°C increase in body core temperature above resting levels). However, these guidelines employ a "one size fits all" approach to exposure limits that does not consider individual variation (e.g., age) between workers. Moreover, they fail to provide direction on the safe, initial stay times before these heat-mitigation controls should be employed (i.e., rest breaks) in conditions exceeding upper heat stress limits. While recent work has generated estimates of the initial stay times for young to older men before heat-mitigation controls are required for moderate-intensity work, information on initial stay times for heavy-intensity work remains to be assessed. This project will assess the initial stay times for heavy-intensity work for a single work bout as well as for a second work bout that is preceded by an extended rest period such as a lunch break and a work bout performed on the next day to determine if refinements in initial stay times across these periods may be required. Further, the investigators will evaluate if the application of recommended work-rest allocations thereafter would alleviate increases in core temperature for the duration of the work period (e.g., start of shift versus post-lunch period). Given the known age-differences in heat loss that can modulate core temperature regulation during an exercise-heat stress, the investigators will assess responses response in young and older adults.
研究设计
- 研究类型
- Interventional
- 分配方式
- Non Randomized
- 干预模型
- Parallel
- 主要目的
- Basic Science
- 盲法
- Single (Outcomes Assessor)
入排标准
- 年龄范围
- 18 Years 至 69 Years（Adult, Older Adult）
- 性别
- Male
- 接受健康志愿者
- 是
入选标准
- •young (18-30 years) and older adults (50-69 years)
- •habitually active, not endurance trained (<2 sessions per week, <150 minutes per week)
- •non-smoking
- •English or French speaking
- •ability to provide informed consent
排除标准
- •pre-existing health conditions (e.g., diabetes, hypertension)
- •use of medication deemed to significantly modulate thermoregulatory function and heat tolerance (e.g., antidepressants, antihistamines, diuretics)
- •engaged in jobs and/or activities that involve frequent exposure to hot environments (e.g., regular sauna use)
研究组 & 干预措施
Younger adults.
Adults aged 18-30 years with no pre-existing health conditions
干预措施: Simulated work in the heat (Other)
Older adults. Adults aged 50-69 with no pre-existing health conditions
Adults aged 50-69 with no pre-existing health conditions
干预措施: Simulated work in the heat (Other)
结局指标
主要结局
Average core temperature
时间窗: Period of work-rest allocations following initial stay time for morning of day 2
Average core temperature following initial stay time
Initial stay time
时间窗: End of third (morning day 2) continuous work bout
Total continuous work time to achieve an initial absolute increase in core temperature of 38°C (equivalent to a 1°C increase in body core temperature above resting levels) (note: in instances where a participant voluntarily terminates work prematurely before the absolute core temperature of ≥38°C (or relative increase of ≥1°C) is achieved or the absolute core temperature is \<38°C (or relative increase of \<1°C), the time of termination or end of the work bout will be taken as the initial stay time respectively).
Initial stay time
时间窗: End of first (morning day 1) continuous work bout
Total continuous work time to achieve an initial absolute increase in core temperature of 38°C (equivalent to a 1°C increase in body core temperature above resting levels) (note: in instances where a participant voluntarily terminates work prematurely before the absolute core temperature of ≥38°C (or relative increase of ≥1°C) is achieved or the absolute core temperature is \<38°C (or relative increase of \<1°C), the time of termination or end of the work bout will be taken as the initial stay time respectively).
Initial stay time
时间窗: End of second (afternoon day 1) continuous work bout
Total continuous work time to achieve an initial absolute increase in core temperature of 38°C (equivalent to a 1°C increase in body core temperature above resting levels) (note: in instances where a participant voluntarily terminates work prematurely before the absolute core temperature of ≥38°C (or relative increase of ≥1°C) is achieved or the absolute core temperature is \<38°C (or relative increase of \<1°C), the time of termination or end of the work bout will be taken as the initial stay time respectively).
Average core temperature
时间窗: Period of work-rest allocations following initial stay time for morning day 1
Average core temperature following initial stay time
Average core temperature
时间窗: Period of work-rest allocations following initial stay time for afternoon day 1
Average core temperature following initial stay time
次要结局
- Fluid loss(End of third (morning day 2) work period)
- Thermal comfort scale(Period of work-rest allocations following initial stay time for morning of day 2)
- Fluid consumption(End of third (morning day 2) work period)
- Systolic blood pressure(End of third (morning day 2) work period)
- Skin temperature at initial stay time(End of first (morning day 2) continuous work bout)
- Average skin temperature(Period of work-rest allocations following initial stay time for morning of day 2)
- Mean arterial pressure(End of third (morning day 2) work period)
- Rating of Perceived Exertion(Period of work-rest allocations following initial stay time for morning of day 2)
- Heart rate at initial stay time(End of first (morning day 2) continuous work bout)
- Rate pressure product(End of third (morning day 2) work period)
- Average heart rate(Period of work-rest allocations following initial stay time for morning of day 2)
- Diastolic blood pressure(End of third (morning day 1) work period)
- Change in plasma volume(End of third (morning day 2) work period)
- Thirst sensation scale(Period of work-rest allocations following initial stay time for morning of day 2)
- Orthostatic Intolerance Symptoms Assessment(End of third (afternoon day 1) continuous work bout)
- Heart rate at initial stay time(End of first (morning day 1) continuous work bout)
- Heart rate at initial stay time(End of first (afternoon day 1) continuous work bout)
- Average heart rate(Period of work-rest allocations following initial stay time for morning of day 1)
- Average heart rate(Period of work-rest allocations following initial stay time for afternoon of day 1)
- Skin temperature at initial stay time(End of first (morning day 1) continuous work bout)
- Skin temperature at initial stay time(End of first (afternoon day 1) continuous work bout)
- Average skin temperature(Period of work-rest allocations following initial stay time for morning of day 1)
- Average skin temperature(Period of work-rest allocations following initial stay time for afternoon of day 1)
- Systolic blood pressure(End of first (morning day 1) work period)
- Systolic blood pressure(End of second (afternoon day 1) work period)
- Diastolic blood pressure(End of first (morning day 1) work period)
- Diastolic blood pressure(End of second (afternoon day 1) work period)
- Mean arterial pressure(End of first (morning day 1) work period)
- Mean arterial pressure(End of second (afternoon day 1) work period)
- Rate pressure product(End of first (morning day 1) work period)
- Rate pressure product(End of second (afternoon day 1) work period)
- Fluid consumption(End of first (morning day 1) work period)
- Fluid consumption(End of second (afternoon day 1) work period)
- Fluid loss(End of first (morning day 1) work period)
- Fluid loss(End of second (afternoon day 1) work period)
- Change in plasma volume(End of first (morning day 1) work period)
- Change in plasma volume(End of second (afternoon day 1) work period)
- Thirst sensation scale(End of first (morning day 1) continuous work bout)
- Thermal comfort scale(End of first (morning day 1) continuous work bout)
- Thermal comfort scale(End of second (afternoon day 1) continuous work bout)
- Thermal comfort scale(End of third (morning day 2) continuous work bout)
- Thermal comfort scale(Period of work-rest allocations following initial stay time for morning of day 1)
- Thermal comfort scale(Period of work-rest allocations following initial stay time for afternoon of day 1)
- Thirst sensation scale(End of second (afternoon day 1) continuous work period)
- Thirst sensation scale(End of third (morning day 2) continuous work period)
- Thirst sensation scale(Period of work-rest allocations following initial stay time for morning of day 1)
- Thirst sensation scale(Period of work-rest allocations following initial stay time for afternoon day 2)
- Rating of Perceived Exertion(End of first (morning day 1) continuous work bout)
- Rating of Perceived Exertion(End of second (afternoon day 1) continuous work bout)
- Rating of Perceived Exertion(End of third (morning day 2) continuous work bout)
- Rating of Perceived Exertion(Period of work-rest allocations following initial stay time for morning of day 1)
- Rating of Perceived Exertion(Period of work-rest allocations following initial stay time for afternoon of day 1)
- Orthostatic Intolerance Symptoms Assessment(End of first (morning day 1) continuous work bout)
- Orthostatic Intolerance Symptoms Assessment(End of second (afternoon day 1) continuous work bout)
研究者
Glen P. Kenny
Principal investigator
University of Ottawa