Abstract
Purpose
Time-weighted averaging is used in occupational heat stress guidelines to estimate the metabolic demands of variable-intensity work. However, compared to constant-intensity work of the same time-weighted average metabolic rate, variable-intensity work may cause decrements in total heat loss (dry + evaporative heat loss) that exacerbate heat storage in women. We therefore used direct calorimetry to assess whole-body total heat loss and heat storage (metabolic heat production minus total heat loss) in women and men during constant- and variable-intensity work of equal average intensity.
Methods
Ten women [mean (SD); 31 (11) years] and fourteen men [30 (8) years] completed two trials involving 90-min of constant- and variable-intensity work (cycling) eliciting an average metabolic heat production of ~ 200 W/m2 in dry-heat (40 °C, ~ 15% relative humidity). External work was fixed at ~ 40 W/m2 for constant-intensity work, and alternated between ~ 15 and ~ 60 W/m2 (5-min each) for variable-intensity work.
Results
When expressed as a time-weighted average over each work period, total heat loss did not differ between men and women (mean difference [95% CI]; 4 W/m2 [− 11, 20]; p = 0.572) or between constant- and variable-intensity work (1 W/m2 [− 3, 5]; p = 0.642). Consequently, heat storage did not differ significantly between men and women (− 4 W/m2 [− 17, 8]; p = 0.468) or between constant- and variable-intensity work (0 W/m2 [− 3, 3]; p = 0.834).
Conclusion
Neither whole-body heat loss nor heat storage was modulated by the partitioning of work intensity, indicating that time-weighted averaging is appropriate for estimating metabolic demand to assess occupational heat stress in women.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
Abbreviations
- A D :
-
Body surface area
- CON:
-
Constant-intensity work
- DHL:
-
Dry heat loss
- EHL:
-
Evaporative heat loss
- E req :
-
Evaporative requirement for heat loss
- HR:
-
Heart rate
- T re :
-
Rectal temperature
- T sk :
-
Mean skin temperature
- LBM:
-
Lean body mass
- LSR:
-
Local sweat rate
- M-W:
-
Metabolic heat production
- VAR:
-
Variable-intensity work
- \(\dot{V}{\text{O}}_{2}\) peak:
-
Peak oxygen consumption
- WBSR:
-
Whole-body sweat rate
References
ACGIH (2008) TLVs and BEIs based on the documentation of the threshold limit values for chemical substances and physical agents, and biological exposure indices. Cincinnati, Ohio
Avellini BA, Kamon E, Krajewski JT (1980) Physiological responses of physically fit men and women to acclimation to humid heat. J Appl Physiol Respir Environ Exerc Physiol 49(2):254–261. https://doi.org/10.1152/jappl.1980.49.2.254
Charkoudian N, Stachenfeld NS (2014) Reproductive hormone influences on thermoregulation in women. Compr Physiol 4(2):793–804. https://doi.org/10.1002/cphy.c130029
CSEP (1986) Certified Fitness Appraiser Resource Manual. Canadian Society for Exercise Physiology, Gloucester, Ontario, Determination of aerobic power
D'Souza AW, Notley SR, Kenny GP (2020) The relation between age and sex on whole-body heat loss during exercise-heat stress. Med Sci Sports Exerc. https://doi.org/10.1249/MSS.0000000000002373
Du Bois D, Du Bois EF (1916) Clinical calorimetry: tenth paper a formula to estimate the approximate surface area if height and weight be known. Arch Int Med 17(6.2):863–871
Ekblom B, Greenleaf CJ, Greenleaf JE, Hermansen L (1971) Temperature regulation during continuous and intermittent exercise in man. Acta Physiol 81(1):1–10
Faul F, Erdfelder E, Lang AG, Buchner A (2007) G*Power 3: a flexible statistical power analysis program for the social, behavioral, and biomedical sciences. Behav Res Methods 39(2):175–191. https://doi.org/10.3758/bf03193146
Flouris AD, Dinas PC, Ioannou LG, Nybo L, Havenith G, Kenny GP, Kjellstrom T (2018) Workers' health and productivity under occupational heat strain: a systematic review and meta-analysis. Lancet Planet Health 2(12):e521–e531. https://doi.org/10.1016/S2542-5196(18)30237-7
Gagnon D, Crandall CG, Kenny GP (2013) Sex differences in postsynaptic sweating and cutaneous vasodilation. J Appl Physiol 114(3):394–401. https://doi.org/10.1152/japplphysiol.00877.2012
Gagnon D, Kenny GP (2011) Sex modulates whole-body sudomotor thermosensitivity during exercise. J Physiol 589(Pt 24):6205–6217. https://doi.org/10.1113/jphysiol.2011.219220
Gagnon D, Kenny GP (2012) Sex differences in thermoeffector responses during exercise at fixed requirements for heat loss. J Appl Physiol 113(5):746–757. https://doi.org/10.1152/japplphysiol.00637.2012
Graveling RA, Morris LA (1995) Influence of intermittency and static components of work on heat stress. Ergonomics 38(1):101–114. https://doi.org/10.1080/00140139508925088
Hardy JD, Du Bois EF (1940) Differences between men and women in their response to heat and cold. Proc Natl Acad Sci U S A 26(6):389–398. https://doi.org/10.1073/pnas.26.6.389
Havenith G, van Middendorp H (1990) The relative influence of physical fitness, acclimatization state, anthropometric measures and gender on individual reactions to heat stress. Eur J Appl Physiol Occup Physiol 61(5–6):419–427. https://doi.org/10.1007/bf00236062
ISO (2004) Ergonomics of the thermal environment—determination of metabolic rate. International Organization for Standardization Geneva, Switzerland
Jacklitsch BL, Williams WJ, Musolin K, Coca A, Kim J-H, Turner N (2016) Occupational exposure to heat and hot environments: revised criteria 2016. Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health
Kenefick RW, Cheuvront SN (2012) Hydration for recreational sport and physical activity. Nutr Rev 70(Suppl 2):S137–142. https://doi.org/10.1111/j.1753-4887.2012.00523.x
Kenny GP, Jay O (2013) Thermometry, calorimetry, and mean body temperature during heat stress. Compr Physiol 3(4):1689–1719. https://doi.org/10.1002/cphy.c130011
Kenny GP, Vierula M, Mate J, Beaulieu F, Hardcastle SG, Reardon F (2012) A field evaluation of the physiological demands of miners in Canada's deep mechanized mines. J Occup Environ Hyg 9(8):491–501. https://doi.org/10.1080/15459624.2012.693880
Kolka MA, Stephenson LA (1989) Control of sweating during the human menstrual cycle. Eur J Appl Physiol Occup Physiol 58(8):890–895. https://doi.org/10.1007/bf02332224
Kraning KK 2nd (1985) Gonzalez RR (1991) Physiological consequences of intermittent exercise during compensable and uncompensable heat stress. J Appl Physiol 71(6):2138–2145. https://doi.org/10.1152/jappl.1991.71.6.2138
Lamarche DT, Notley SR, Louie JC, Poirier MP, Kenny GP (2018a) Fitness-related differences in the rate of whole-body evaporative heat loss in exercising men are heat-load dependent. Exp Physiol 103(1):101–110. https://doi.org/10.1113/EP086637
Lamarche DT, Notley SR, Poirier MP, Kenny GP (2018b) Fitness-related differences in the rate of whole-body total heat loss in exercising young healthy women are heat-load dependent. Exp Physiol 103(3):312–317. https://doi.org/10.1113/EP086752
Lei TH, Cotter JD, Schlader ZJ, Stannard SR, Perry BG, Barnes MJ, Mundel T (2019) On exercise thermoregulation in females: interaction of endogenous and exogenous ovarian hormones. J Physiol 597(1):71–88. https://doi.org/10.1113/JP276233
Lind AR (1963a) A physiological criterion for setting thermal environmental limits for everyday work. J Appl Physiol 18:51–56. https://doi.org/10.1152/jappl.1963.18.1.51
Lind AR (1963b) Physiological effects of continuous or intermittent work in the heat. J Appl Physiol 18:57–60. https://doi.org/10.1152/jappl.1963.18.1.57
Loe H, Rognmo Ø, Saltin B, Wisløff U (2013) Aerobic capacity reference data in 3816 healthy men and women 20–90 years. PLoS ONE 8(5):e64319
McLellan TM, Daanen HA, Cheung SS (2013) Encapsul Environ Compr Physiol 3(3):1363–1391. https://doi.org/10.1002/cphy.c130002
Meade RD, Lauzon M, Poirier MP, Flouris AD, Kenny GP (2015) An evaluation of the physiological strain experienced by electrical utility workers in North America. J Occup Environ Hyg 12(10):708–720. https://doi.org/10.1080/15459624.2015.1043054
Meade RD, Lauzon M, Poirier MP, Flouris AD, Kenny GP (2016) The physical demands of electrical utilities work in North America. J Occup Environ Hyg 13(1):60–70. https://doi.org/10.1080/15459624.2015.1077966
Mora-Rodriguez R, Del Coso J, Estevez E (2008) Thermoregulatory responses to constant versus variable-intensity exercise in the heat. Med Sci Sports Exerc 40(11):1945–1952. https://doi.org/10.1249/MSS.0b013e31817f9843
Notley SR, Dervis S, Poirier MP (1985) Kenny GP (2019a) Menstrual cycle phase does not modulate whole body heat loss during exercise in hot, dry conditions. J Appl Physiol 126(2):286–293. https://doi.org/10.1152/japplphysiol.00735.2018
Notley SR, Flouris AD, Kenny GP (2019a) Occupational heat stress management: does one size fit all? Am J Ind Med 62(12):1017–1023. https://doi.org/10.1002/ajim.22961
Notley SR, Lamarche DT, Meade RD, Flouris AD, Kenny GP (2019b) Revisiting the influence of individual factors on heat exchange during exercise in dry heat using direct calorimetry. Exp Physiol 104(7):1038–1050. https://doi.org/10.1113/EP087666
Notley SR, Meade RD, D'Souza AW, Rutherford MM, Kim J-H, Kenny GP (2020) Heat exchange in young and older men during constant-and variable-intensity work. Med Sci Sports Exerc. https://doi.org/10.1249/MSS.0000000000002410
Notley SR, Park J, Tagami K, Ohnishi N, Taylor NAS (2017) Variations in body morphology explain sex differences in thermoeffector function during compensable heat stress. Exp Physiol 102(5):545–562. https://doi.org/10.1113/EP086112
Ramanathan NL (1964) A new weighting system for mean surface temperature of the human body. J Appl Physiol 19:531–533. https://doi.org/10.1152/jappl.1964.19.3.531
Reardon FD, Leppik KE, Wegmann R, Webb P, Ducharme MB, Kenny GP (2006) The Snellen human calorimeter revisited, re-engineered and upgraded: design and performance characteristics. Med Biol Eng Comput 44(8):721–728. https://doi.org/10.1007/s11517-006-0086-5
Siri WE (1956) The gross composition of the body. Adv Biol Med Phys 4:239–280. https://doi.org/10.1016/b978-1-4832-3110-5.50011-x
Solis HL, Hall K (2009) Women in the labor force: a databook. US Bureau Labor Stat Rep 1018:1–101
Taylor NA, Fullagar HH, Sampson JA, Notley SR, Burley SD, Lee DS, Groeller H (2015) Employment standards for Australian urban firefighters: Part 2: the physiological demands and the criterion tasks. J Occup Environ Med 57(10):1072–1082. https://doi.org/10.1097/JOM.0000000000000526
Taylor NA, Lewis MC, Notley SR, Peoples GE (2012) A fractionation of the physiological burden of the personal protective equipment worn by firefighters. Eur J Appl Physiol 112(8):2913–2921. https://doi.org/10.1007/s00421-011-2267-7
Todd G, Gordon CJ, Groeller H, Taylor NA (2014) Does intramuscular thermal feedback modulate eccrine sweating in exercising humans? Acta Physiol 212(1):86–96
WHO (1969) Health factors involved in working under conditions of heat stress: report of a WHO scientific group. HM Stationery Office,
Wyndham CH, Morrison JF, Williams CG (1965) Heat reactions of male and female Caucasians. J Appl Physiol 20(3):357–364. https://doi.org/10.1152/jappl.1965.20.3.357
Yamazaki F, Sone R (1985) Ikegami H (1994) Responses of sweating and body temperature to sinusoidal exercise. J Appl Physiol 76(6):2541–2545. https://doi.org/10.1152/jappl.1994.76.6.2541
Acknowledgements
We thank all the participants who volunteered for the present study.
Funding
This research was in part supported by the Government of Ontario, Canada (all funds held by Dr. Glen P. Kenny). G.P. Kenny is supported by a University of Ottawa Research Chair. S.R. Notley is supported by a Postdoctoral Fellowship from the Human and Environmental Physiology Research Unit. A.W. D’Souza (CGS-M) was supported by Natural Sciences and Engineering Council of Canada Alexander Graham Bell Graduate Scholarship. R.D. Meade was supported by an Ontario Graduate Scholarship. At the time of the study, A.W. D’Souza was a graduate trainee (MSc) at HEPRU under supervision of G.P. Kenny. He is currently completed his doctoral thesis at the Neurovascular Research Laboratory, School of Kinesiology, Western University, London, ON, Canada.
Author information
Authors and Affiliations
Contributions
SRN, RDM, and GPK conceptualized and designed the research; SRN, AWD, RDM, and BJR performed experiments; SRN analyzed data, prepared figures, and drafted the manuscript. All authors interpreted the results of experiments, edited and revised the manuscript, and approved the final version.
Corresponding author
Ethics declarations
Conflict of interest
No conflict of interest, financial or otherwise, is declared by the author(s).
Additional information
Communicated by Narihiko Kondo.
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Notley, S.R., D’Souza, A.W., Meade, R.D. et al. Whole-body heat exchange in women during constant- and variable-intensity work in the heat. Eur J Appl Physiol 120, 2665–2675 (2020). https://doi.org/10.1007/s00421-020-04486-3
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00421-020-04486-3