Journal
PLOS ONE
Volume 10, Issue 3, Pages -Publisher
PUBLIC LIBRARY SCIENCE
DOI: 10.1371/journal.pone.0119079
Keywords
-
Categories
Funding
- Canadian Institutes of Health Research [286363]
- Leaders Opportunity Fund from the Canada Foundation for Innovation
- University of Ottawa Research Chair Award
- Human and Environmental Physiology Research Unit
- Queen Elizabeth II graduate scholarships in science and technology
- Ontario's Ministry of Training, Colleges, and Universities
Ask authors/readers for more resources
Studies have reported that older females have impaired heat loss responses during work in the heat compared to young females. However, it remains unclear at what level of heat stress these differences occur. Therefore, we examined whole-body heat loss [evaporative (H-E) and dry heat loss, via direct calorimetry] and changes in body heat storage (Delta H-b, via direct and indirect calorimetry) in 10 young (23 +/- 4 years) and 10 older (58 +/- 5 years) females matched for body surface area and aerobic fitness (VO(2)peak) during three 30-min exercise bouts performed at incremental rates of metabolic heat production of 250 (Ex1), 325 (Ex2) and 400 (Ex3) Win the heat (40 degrees C, 15% relative humidity). Exercise bouts were separated by 15 min of recovery. Since dry heat gain was similar between young and older females during exercise (p=0.52) and recovery (p=0.42), differences in whole-body heat loss were solely due to HE. Our results show that older females had a significantly lower H-E at the end of Ex2 (young: 383 +/- 34 W; older: 343 +/- 39 W, p=0.04) and Ex3 (young: 437 +/- 36 W; older: 389 +/- 29 W, p=0.008), however no difference was measured at the end of Ex1 (p=0.24). Also, the magnitude of difference in the maximal level of HE achieved between the young and older females became greater with increasing heat loads (Ex1=10.2%, Ex2=11.6% and Ex3=12.4%). Furthermore, a significantly greater Delta H-b was measured for all heat loads for the older females (Ex1: 178 +/- 44 kJ; Ex2: 151 +/- 38 kJ; Ex3: 216 +/- 25 kJ, p=0.002) relative to the younger females (Ex1: 127 +/- 35 kJ; Ex2: 96 +/- 45 kJ; Ex3: 146 +/- 46 kJ). In contrast, no differences in HE or Delta H-b were observed during recovery (p>0.05). We show that older habitually active females have an impaired capacity to dissipate heat compared to young females during exercise-induced heat loads of >= 325 W when performed in the heat.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available