Tags

Type your tag names separated by a space and hit enter

Fitness-related differences in the rate of whole-body total heat loss in exercising young healthy women are heat-load dependent.
Exp Physiol 2018; 103(3):312-317EP

Abstract

NEW FINDINGS

What is the central question of this study? Aerobic fitness modulates heat loss, albeit the heat load at which fitness-related differences occur in young healthy women remains unclear. What is the main finding and its importance? We demonstrate using direct calorimetry that fitness modulates heat loss in a heat-load dependent manner, with differences occurring between young women of low and high fitness and matched physical characteristics when the metabolic heat load is at least 400 W in hot, dry conditions. Although fitness has been known for some time to modulate heat loss, our findings define the metabolic heat load at which fitness-related differences occur.

ABSTRACT

Aerobic fitness has recently been shown to alter heat loss capacity in a heat-load dependent manner in young men. However, given that sex-related differences in heat loss capacity exist, it is unclear whether this response is consistent in women. We therefore assessed whole-body total heat loss in young (21 ± 3 years old) healthy women matched for physical characteristics, but with low (low-fit; 35.8 ± 4.5 ml O2 kg-1 min-1) or high aerobic fitness (high-fit; 53.1 ± 5.1 ml O2 kg-1 min-1 ; both n = 8; indexed by peak oxygen consumption), during three 30 min bouts of cycling performed at increasing rates of metabolic heat production of 250 (Ex1), 325 (Ex2) and 400 W (Ex3), each separated by a 15 min recovery, in hot, dry conditions (40°C, 11% relative humidity). Whole-body total heat loss (evaporative ± dry heat exchange) and metabolic heat production were measured using direct and indirect calorimetry, respectively. Body heat content was measured as the temporal summation of heat production and loss. Total heat loss did not differ during Ex1 (low-fit, 215 ± 16 W; high-fit, 231 ± 20 W; P > 0.05) and Ex2 (low-fit, 278 ± 15 W; high-fit, 301 ± 20 W; P > 0.05), but was lower in the low-fit (316 ± 21 W) compared with the high-fit women (359 ± 32 W) during Ex3 (P < 0.01). Consequently, the low-fit group stored 1.3-fold more heat (429 ± 61 kJ) throughout the three exercise bouts relative to the high-fit group (330 ± 113 kJ; P < 0.05). We show that aerobic fitness independently modulates heat loss capacity during exercise in hot, dry conditions in women separated by a peak oxygen consumption of ∼17 ml O2 kg-1 min-1 starting at a metabolic heat load of 400 W.

Authors+Show Affiliations

Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada.Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada.Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada.Human and Environmental Physiology Research Unit, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada.

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

29250845

Citation

Lamarche, Dallon T., et al. "Fitness-related Differences in the Rate of Whole-body Total Heat Loss in Exercising Young Healthy Women Are Heat-load Dependent." Experimental Physiology, vol. 103, no. 3, 2018, pp. 312-317.
Lamarche DT, Notley SR, Poirier MP, et al. Fitness-related differences in the rate of whole-body total heat loss in exercising young healthy women are heat-load dependent. Exp Physiol. 2018;103(3):312-317.
Lamarche, D. T., Notley, S. R., Poirier, M. P., & Kenny, G. P. (2018). Fitness-related differences in the rate of whole-body total heat loss in exercising young healthy women are heat-load dependent. Experimental Physiology, 103(3), pp. 312-317. doi:10.1113/EP086752.
Lamarche DT, et al. Fitness-related Differences in the Rate of Whole-body Total Heat Loss in Exercising Young Healthy Women Are Heat-load Dependent. Exp Physiol. 2018 03 1;103(3):312-317. PubMed PMID: 29250845.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Fitness-related differences in the rate of whole-body total heat loss in exercising young healthy women are heat-load dependent. AU - Lamarche,Dallon T, AU - Notley,Sean R, AU - Poirier,Martin P, AU - Kenny,Glen P, Y1 - 2018/01/19/ PY - 2017/10/13/received PY - 2017/12/13/accepted PY - 2017/12/19/pubmed PY - 2019/1/24/medline PY - 2017/12/19/entrez KW - aerobic fitness KW - exercise KW - females SP - 312 EP - 317 JF - Experimental physiology JO - Exp. Physiol. VL - 103 IS - 3 N2 - NEW FINDINGS: What is the central question of this study? Aerobic fitness modulates heat loss, albeit the heat load at which fitness-related differences occur in young healthy women remains unclear. What is the main finding and its importance? We demonstrate using direct calorimetry that fitness modulates heat loss in a heat-load dependent manner, with differences occurring between young women of low and high fitness and matched physical characteristics when the metabolic heat load is at least 400 W in hot, dry conditions. Although fitness has been known for some time to modulate heat loss, our findings define the metabolic heat load at which fitness-related differences occur. ABSTRACT: Aerobic fitness has recently been shown to alter heat loss capacity in a heat-load dependent manner in young men. However, given that sex-related differences in heat loss capacity exist, it is unclear whether this response is consistent in women. We therefore assessed whole-body total heat loss in young (21 ± 3 years old) healthy women matched for physical characteristics, but with low (low-fit; 35.8 ± 4.5 ml O2 kg-1 min-1) or high aerobic fitness (high-fit; 53.1 ± 5.1 ml O2 kg-1 min-1 ; both n = 8; indexed by peak oxygen consumption), during three 30 min bouts of cycling performed at increasing rates of metabolic heat production of 250 (Ex1), 325 (Ex2) and 400 W (Ex3), each separated by a 15 min recovery, in hot, dry conditions (40°C, 11% relative humidity). Whole-body total heat loss (evaporative ± dry heat exchange) and metabolic heat production were measured using direct and indirect calorimetry, respectively. Body heat content was measured as the temporal summation of heat production and loss. Total heat loss did not differ during Ex1 (low-fit, 215 ± 16 W; high-fit, 231 ± 20 W; P > 0.05) and Ex2 (low-fit, 278 ± 15 W; high-fit, 301 ± 20 W; P > 0.05), but was lower in the low-fit (316 ± 21 W) compared with the high-fit women (359 ± 32 W) during Ex3 (P < 0.01). Consequently, the low-fit group stored 1.3-fold more heat (429 ± 61 kJ) throughout the three exercise bouts relative to the high-fit group (330 ± 113 kJ; P < 0.05). We show that aerobic fitness independently modulates heat loss capacity during exercise in hot, dry conditions in women separated by a peak oxygen consumption of ∼17 ml O2 kg-1 min-1 starting at a metabolic heat load of 400 W. SN - 1469-445X UR - https://www.unboundmedicine.com/medline/citation/29250845/Fitness_related_differences_in_the_rate_of_whole_body_total_heat_loss_in_exercising_young_healthy_women_are_heat_load_dependent_ L2 - https://doi.org/10.1113/EP086752 DB - PRIME DP - Unbound Medicine ER -