Work-Related Effects of Heat, Activity, and Fat in Middle Aged Men
NCT ID: NCT02532725
Last Updated: 2015-08-26
Study Results
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Basic Information
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COMPLETED
12 participants
OBSERVATIONAL
1972-06-30
1972-12-31
Brief Summary
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This small study evaluates the heat tolerance of lean and obese middle aged men both while exercising and resting and the ways in which each compensate for and dissipate increasing environmental heat and heat generated by the body while exercising.
As obesity is a worldwide public health crisis and as populations in many industrialized nations age, it is important to understand the combined effects of obesity and middle age for men on their ability to safely work in hot environments. Such information will permit establishing and revising of safe work standards and inform public health outreach to the target population, itself.
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Detailed Description
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Importance of Present Study:
Several heat tolerance studies, including Kenny, Gagnon, Dorman, Hardcastle, and Joy (2010), have indicated that middle-age men can perform hard work in hot environments nearly as well as younger men. Dufour and Candas (2007), in comparing passive heat responses and sudomotor function in young, middle aged, and older men, found only local, not global, decreases in sweat gland output in the two older groups, suggesting at least some significant preservation of sudomotor function. Since most studies employed subjects with lean normal body types, their results in terms of physiological reactions to heat stress may not be applicable to obese middle aged men. Other studies have demonstrated degraded heat stress exercise capacity in obese persons.
Within high heat stress areas such as in the steel, fiberglass, aluminium, mining, professional sports, and defense industries, lean and obese middle aged men can readily be observed performing the same work task in the same hot environment. Little attention has been given to differences between the lean and obese middle aged men in their physiological responses to the combination of internal heat production from the work task performed and the heat load imposed from the external environment.
In the present study, occupational heat stress endurance differences between lean and obese middle aged men and effect of obesity are investigated under laboratory simulated conditions to test the following hypotheses: (1) with greater baseline cardiovascular demands, it is expected that obese middle aged men will have reduced environmental heat tolerance and will gain and store more total heat; (2) poorer environmental heat tolerance of obese middle aged men will be greatly magnified by work (producing added metabolic heat); (3) lean middle aged men will thermoregulate well; (4) lean middle aged men will show few, if any, major signs of inability to compensate for added cardiovascular demands; (5) obese middle aged men will be functioning at a higher percentage of their maximal ventilation of expired oxygen; and (6) obese middle aged men will have poorer pulmonary fitness, as measured by maximal ventilation of expired oxygen, than lean middle aged men.
Conditions
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Study Design
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CASE_CONTROL
PROSPECTIVE
Study Groups
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Lean
Men aged 35-55 years, having \<20% body fat
Cardiopulmonary Exercise Stress Test
Test preceded by warm-up treadmill walking 5 min at 4.8 km/h, 5% grade with a 1 min sitting rest period. Test, then, begins at 4.8 km/h, 2.5% grade with incremental grade increases every 2 min until exhaustion. Ambient environment is maintained at neutral, with effective temperature of 19-21° C. Heart, lungs, temperature, and sweating is monitored during testing.
Climatic-Controlled Cardiopulmonary Exercise Stress Test
Test includes 30 min walking bouts on the treadmill, with two 5 min sitting rest periods between bouts (Rest I and Rest II) and 15 min sitting recovery period (Rest III), in effective temperatures of 21.1 (baseline), 26.7, 29.4, 32.2, and 35.0° C. Heart, lungs, temperature, and sweating is monitored during testing.
Body Composition Evaluation
Multiple methods are used to accurately estimate percentage of body mass (weight) composed of fat, muscle, bone, and other connective tissues. Four different methods, including caliper and hydrostatic (underwater weighing) are used in this study to ensure an accurate estimation.
Pre-Exercise Risk Assessment
Includes non-invasive measurements of body functioning, a physical examination by a physician, and blood and urine testing to select subjects who can exercise with relative safety.
Obese
Men aged 35-55 years, having \>29% body fat
Cardiopulmonary Exercise Stress Test
Test preceded by warm-up treadmill walking 5 min at 4.8 km/h, 5% grade with a 1 min sitting rest period. Test, then, begins at 4.8 km/h, 2.5% grade with incremental grade increases every 2 min until exhaustion. Ambient environment is maintained at neutral, with effective temperature of 19-21° C. Heart, lungs, temperature, and sweating is monitored during testing.
Climatic-Controlled Cardiopulmonary Exercise Stress Test
Test includes 30 min walking bouts on the treadmill, with two 5 min sitting rest periods between bouts (Rest I and Rest II) and 15 min sitting recovery period (Rest III), in effective temperatures of 21.1 (baseline), 26.7, 29.4, 32.2, and 35.0° C. Heart, lungs, temperature, and sweating is monitored during testing.
Body Composition Evaluation
Multiple methods are used to accurately estimate percentage of body mass (weight) composed of fat, muscle, bone, and other connective tissues. Four different methods, including caliper and hydrostatic (underwater weighing) are used in this study to ensure an accurate estimation.
Pre-Exercise Risk Assessment
Includes non-invasive measurements of body functioning, a physical examination by a physician, and blood and urine testing to select subjects who can exercise with relative safety.
Interventions
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Cardiopulmonary Exercise Stress Test
Test preceded by warm-up treadmill walking 5 min at 4.8 km/h, 5% grade with a 1 min sitting rest period. Test, then, begins at 4.8 km/h, 2.5% grade with incremental grade increases every 2 min until exhaustion. Ambient environment is maintained at neutral, with effective temperature of 19-21° C. Heart, lungs, temperature, and sweating is monitored during testing.
Climatic-Controlled Cardiopulmonary Exercise Stress Test
Test includes 30 min walking bouts on the treadmill, with two 5 min sitting rest periods between bouts (Rest I and Rest II) and 15 min sitting recovery period (Rest III), in effective temperatures of 21.1 (baseline), 26.7, 29.4, 32.2, and 35.0° C. Heart, lungs, temperature, and sweating is monitored during testing.
Body Composition Evaluation
Multiple methods are used to accurately estimate percentage of body mass (weight) composed of fat, muscle, bone, and other connective tissues. Four different methods, including caliper and hydrostatic (underwater weighing) are used in this study to ensure an accurate estimation.
Pre-Exercise Risk Assessment
Includes non-invasive measurements of body functioning, a physical examination by a physician, and blood and urine testing to select subjects who can exercise with relative safety.
Other Intervention Names
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Eligibility Criteria
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Inclusion Criteria
* Non-invasive resting blood pressure within normal limits
* Resting electrocardiogram within normal limits
* Hematology and Chemistry (blood) panels within normal limits
* Urinalysis (pH, glucose, and protein) within normal limits
* Negative cardiopulmonary stress test
* Absence of acute or chronic metabolic, cardiovascular, pulmonary, and orthopedic disease
Exclusion Criteria
* Non-invasive resting blood pressure outside normal limits
* Resting electrocardiogram outside normal limits
* Hematology and Chemistry (blood) panels outside normal limits
* Urinalysis (pH, glucose, and protein) outside normal limits
* Positive cardiopulmonary stress test
* Presence of acute or chronic metabolic, cardiovascular, pulmonary, and orthopedic disease
35 Years
55 Years
MALE
Yes
Sponsors
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Freeman-Sheldon Research Group, Inc.
OTHER
Responsible Party
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Principal Investigators
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Rodger J McCormick, DEd
Role: PRINCIPAL_INVESTIGATOR
Freeman-Sheldon Research Group, Inc.
Locations
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Freeman-Sheldon Research Group, Inc. Headquarters
Buckhannon, West Virginia, United States
Countries
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References
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Haymes EM, McCormick RJ, Buskirk ER. Heat tolerance of exercising lean and obese prepubertal boys. J Appl Physiol. 1975 Sep;39(3):457-61. doi: 10.1152/jappl.1975.39.3.457.
Kenny GP, Gagnon D, Dorman LE, Hardcastle SG, Jay O. Heat balance and cumulative heat storage during exercise performed in the heat in physically active younger and middle-aged men. Eur J Appl Physiol. 2010 May;109(1):81-92. doi: 10.1007/s00421-009-1266-4. Epub 2009 Nov 3.
Dufour A, Candas V. Ageing and thermal responses during passive heat exposure: sweating and sensory aspects. Eur J Appl Physiol. 2007 May;100(1):19-26. doi: 10.1007/s00421-007-0396-9. Epub 2007 Jan 23.
Related Links
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Freeman-Sheldon Research Group, Inc. (Sponsor's general website)
Other Identifiers
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U1111-1120-6134
Identifier Type: -
Identifier Source: org_study_id
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