Heat Exchange in Young and Older Men during Constant- and Variable-Intensity Work.
Adult
Age Factors
Aged
Bicycling
/ physiology
Body Temperature
/ physiology
Body Temperature Regulation
/ physiology
Calorimetry
/ methods
Energy Metabolism
/ physiology
Heart Rate
/ physiology
Hot Temperature
Humans
Humidity
Middle Aged
Rectum
/ physiology
Specific Gravity
Sweating
/ physiology
Thermogenesis
/ physiology
Time Factors
Urine
/ chemistry
Work
/ physiology
Young Adult
Journal
Medicine and science in sports and exercise
ISSN: 1530-0315
Titre abrégé: Med Sci Sports Exerc
Pays: United States
ID NLM: 8005433
Informations de publication
Date de publication:
12 2020
12 2020
Historique:
pubmed:
21
5
2020
medline:
27
4
2021
entrez:
21
5
2020
Statut:
ppublish
Résumé
Current occupational heat stress guidelines rely on time-weighted averaging to quantify the metabolic demands of variable-intensity work. However, variable-intensity work may be associated with impairments in whole-body total heat loss (dry + evaporative heat loss), especially in older workers, which exacerbate heat strain relative to constant-intensity work eliciting the same time-weighted average metabolic rate. We, therefore, used direct calorimetry to evaluate whether variable-intensity work would cause decrements in the average rate of whole-body total heat loss that augment body heat storage and core temperature compared with constant-intensity work in young and older men. Eight young (19-31 yr) and eight older (54-65 yr) men completed four trials involving 90 min of work (cycling) eliciting an average metabolic heat production of ~200 W·m in dry-heat (40°C, 20% relative humidity). One trial involved constant-intensity work (CON), whereas the others involved 10-min cycles of variable-intensity work: 5-min low-intensity and 5-min high-intensity (VAR 5:5), 6-min low-intensity and 4-min very high-intensity (VAR 6:4), and 7-min low- and 3-min very, very high-intensity (VAR 7:3). Metabolic heat production, total heat loss, body heat storage (heat production minus total heat loss), and core (rectal) temperature were measured throughout. When averaged over each 90-min work period, metabolic heat production, total heat loss, and heat storage were similar between groups and conditions (all P ≥ 0.152). Peak core temperature (average of final 10 min) was also similar between groups and conditions (both P ≥ 0.111). Whole-body total heat loss, heat storage, and core temperature were not significantly influenced by the partitioning of work intensity in young or older men, indicating that time-weighted averaging appears to be appropriate for quantifying the metabolic demands of variable-intensity work to assess occupational heat stress.
Identifiants
pubmed: 32433432
doi: 10.1249/MSS.0000000000002410
pii: 00005768-202012000-00017
doi:
Types de publication
Journal Article
Research Support, Non-U.S. Gov't
Langues
eng
Sous-ensembles de citation
IM
Pagination
2628-2636Références
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