Aerobic fitness as a parameter of importance for labour loss in the heat

Research output: Contribution to journalJournal articleResearchpeer-review

  • Josh Foster
  • James W Smallcombe
  • Simon G Hodder
  • Ollie Jay
  • Andreas D Flouris
  • Nathan Bradley Morris
  • Nybo, Lars
  • George Havenith

Objectives: To derive an empirical model for the impact of aerobic fitness (maximal oxygen consumption; V̇O2max in mL∙kg-1∙min-1) on physical work capacity (PWC) in the heat.

Design: Prospective, repeated measures.

Methods: Total work completed during 1 h of treadmill walking at a fixed heart rate of 130 b∙min-1 was assessed in 19 young adult males across a variety of warm and hot climate types, characterised by wet-bulb globe temperatures (WBGT) ranging from 12 to 40 °C. For data presentation and obtaining initial parameter estimates for modelling, participants were grouped into low (n = 6, 74 trials), moderate (n = 8, 76 trials), and high (n = 5, 29 trials) fitness, with group mean V̇O2max 42, 52, and 64 mL∙kg-1∙min-1, respectively. For the heated conditions (WBGT 18 to 40 °C), we calculated PWC% by expressing total energy expenditure (kJ above resting) in each trial relative to that achieved in a cool reference condition (WBGT = 12 °C = 100% PWC).

Results: The relative reduction in energy expenditure (PWC%) caused by heat was significantly smaller by up to 16% for the fit participants compared to those with lower aerobic capacity. V̇O2max also modulated the relationship between sweat rate and body temperature changes to increasing WBGT. Including individual V̇O2max data in the PWC prediction model increased the predicting power by 4%.

Conclusions: Incorporating individual V̇O2max improved the predictive power of the heat stress index WBGT for Physical Work Capacity in the heat. The largest impact of V̇O2max on PWC was observed at a WBGT between 25 and 35 °C.

Original languageEnglish
JournalJournal of Science and Medicine in Sport
ISSN1440-2440
DOIs
Publication statusE-pub ahead of print - 8 May 2021

Bibliographical note

Copyright © 2021 Elsevier Ltd. All rights reserved.

    Research areas

  • Faculty of Science - Heat, Productivity, Fitness, Performance, Work, Climate change

ID: 271759196