Graduation Year

2005

Document Type

Thesis

Degree

M.S.P.H.

Degree Granting Department

Public Health

Major Professor

Thomas E. Bernard, Ph.D.

Committee Member

Candi D. Ashley, Ph.D.

Committee Member

Steven P. Mlynarek, Ph.D.

Keywords

Heat stress, Gender differences, Core temperature, WBGT, Clothing

Abstract

Three main factors that influence heat stress are clothing, work demands and environmental conditions. Gender may also influence the amount of heat stress an individual can tolerate. The purpose of this study was to examine the role of gender in heat stress limits (critical WBGT) and heat strain (heart rate and core temperature). The null hypothesis was that there was no gender difference among critical WBGT, heart rate and core temperature.

Fifteen subjects (11 men and 4 women) wore five different clothing ensembles (cotton work clothes, cotton coveralls, particle barrier Tyvek, water-barrier/vapor permeable NexGen LS417, and vapor barrier Tychem QC made by Dupont) at three levels of metabolic rate (115, 175 and 250 W m -2). A treadmill was used to set the metabolic workload. A climatic chamber was used to control the environmental conditions. The participants continued to walk on the treadmill until their core temperature (Tre) reached a steady state. Then the air temperature and humidity were slowly increased. The point at which the core temperature increased steadily was defined as the inflection point. Environmental data as well as core temperature and heart rate were recorded at five minute intervals. The critical conditions were noted at five minutes before the inflection point.

Metabolic rate, critical WBGT, core temperature and heart rate were analyzed by 3-way ANOVAs (participants nested by ensemble by metabolic rate) with all two way and three way interactions. Significant differences were observed between genders for metabolic rate and heart rate, but not for core temperature and critical WBGT across metabolic level and ensembles. While there were differences between genders in metabolic rate they did not affect the overall conclusions. The heart rate was significantly higher (12 bpm) for women than for men. Overall, women had the same upper limit of the prescriptive zone as men, their core temperatures were the same at this limit but women had a greater cardiovascular cost reflected in a higher heart rate.

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