The Effects of Thermoregulatory Capacity and Metabolism during Moderate Physical Activity and Humidity in Hot Conditions

Presenter

Remi Hirsh

Campus

UMass Amherst

Sponsor

Michael Busa, Department of Institute for Applied Life Sciences, UMass Amherst

Schedule

Session 4, 2:30 PM - 3:15 PM [Schedule by Time][Poster Grid for Time/Location]

Location

Poster Board A90, Campus Center Auditorium, Row 5 (A81-A100) [Poster Location Map]

Abstract

The ability to thermoregulate in hot and humid environments is critical to preventing exertional heat injury in the workplace. It is unclear whether environmental relative humidity (RH) affects thermoregulatory capacity and metabolism in hot conditions. PURPOSE: Evaluate the difference in thermoregulatory capacity and metabolism, defined by Metabolic Equivalent of Activity (METS), core body temperature (CBT), water loss, and heart rate, during intermittent exercise in hot conditions with differing relative humidity. METHODS: Healthy participants (n=37, age=25.3±7 yrs., Body Mass Index (BMI)=25.3±4.1 kg/m², sex: F=13 M=24) completed intermittent industrial work-related tasks in a 32,500 L metabolic chamber with an ambient temperature of 30°C for 60-180 minutes (mean: 91.1±21.7 min). Tasks were completed under high (n=23, 79±1.9%) or low humidity (n=14, 42.7±4.2%) conditions. Water loss was calculated as (Body Weight_post-session-Body Weight_pre-session)+(Water consumed_{during-session}-Urine excreted_{during-session}). METS were calculated as VO₂/3.5/Body weight. Independent sample t-tests were used to compare the RH groups. Data are presented as Mean±SD. RESULTS: Age (high:24.1±5.3yrs vs. low:27.2±9.3 yrs, p=0.25) and BMI (high:25.1±2.8 kg/m² vs. low:25.5±5.6 kg/m², p=0.83) did not differ between groups. Metabolic activity was not different across RH conditions (METS: high:3.81±1.32 vs. low:4.11±0.49, p=0.54). CBT (high:37.3±0.7 °C vs. low:37.5±0.4 °C, p=0.20) and heart rate (high:110.4±21.7bpm vs. low:117.6±19.5bpm, p=0.37) also did not differ. Water loss was not different when expressed as an absolute value (high:0.7±0.5kg vs. low:0.9±0.3kg p=0.44) or as a percentage of body weight (high:0.9±0.6% vs. low:1.2±0.4% p=0.14). CONCLUSION: These results demonstrate that when completing intermittent moderate-intensity exercise under hot conditions, thermoregulatory capacity and metabolism are unaffected by environmental relative humidity in young, healthy persons.

Keywords

thermoregulation, humidity, metabolism, exercise

Research Area

Sports and Exercise Science + Physiology

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