Work-Related Effects of Heat, Activity, and Fat in Middle Aged Men
| Status: | Completed |
|---|---|
| Conditions: | Obesity Weight Loss |
| Therapuetic Areas: | Endocrinology |
| Healthy: | No |
| Age Range: | 35 - 55 |
| Updated: | 4/21/2016 |
| Start Date: | June 1972 |
| End Date: | December 1972 |
Relationship of Occupational Heat Stress Endurance, Work, and Percentage of Body Fat in Middle Aged Men
Obesity is associated with many undesirable health effects and disease, and middle age is
associated with increased risk for disease. Unfortunately, while others have looked at the
effects of obesity, gender, and middle age, the combined effects of obesity and middle age
on men's ability to do work in hot industrial environments have not been satisfactorily
investigated.
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.
associated with increased risk for disease. Unfortunately, while others have looked at the
effects of obesity, gender, and middle age, the combined effects of obesity and middle age
on men's ability to do work in hot industrial environments have not been satisfactorily
investigated.
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.
The present study was initially approved by and conducted at The Pennsylvania State
University in 1972 for the senior author's (Rodger J McCormick) D.Ed. thesis in Biological
Sciences; funding support was provided by the US National Institute of Arthritis,
Metabolism, and Digestive Diseases Grant AM-08311 and National Institutes of Health Grant
01748. Data re-analysis and representation of that study was first approved in 2011 by and
conducted at the FSRG deGruyter-McKusick Institute of Health Sciences for partial
fulfillment of an MS in Clinical and Applied Physiology being pursued by the junior author
(Mikaela I Poling). No funding was received for this use of existing data.
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.
University in 1972 for the senior author's (Rodger J McCormick) D.Ed. thesis in Biological
Sciences; funding support was provided by the US National Institute of Arthritis,
Metabolism, and Digestive Diseases Grant AM-08311 and National Institutes of Health Grant
01748. Data re-analysis and representation of that study was first approved in 2011 by and
conducted at the FSRG deGruyter-McKusick Institute of Health Sciences for partial
fulfillment of an MS in Clinical and Applied Physiology being pursued by the junior author
(Mikaela I Poling). No funding was received for this use of existing data.
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.
Inclusion Criteria:
- Able and willing to give consent and to complete minimum study procedures, as defined
by the protocol
- 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:
- Unable or unwilling to give consent or to complete minimum study procedures, as
defined by the protocol
- 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
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