Josh Foster1, James W Smallcombe1, Simon G Hodder1, Ollie Jay2, Andreas D Flouris3, Nathan B Morris4, Lars Nybo4, George Havenith5. 1. Environmental Ergonomics Research Centre, School of Design and Creative Arts, Loughborough University, UK. 2. The University of Sydney, Thermal Ergonomics Laboratory, Faculty of Medicine and Health, Australia. 3. FAME Laboratory, Department of Physical Education and Sport Science, University of Thessaly, Greece. 4. Department of Nutrition, Exercise and Sports, University of Copenhagen, Denmark. 5. Environmental Ergonomics Research Centre, School of Design and Creative Arts, Loughborough University, UK. Electronic address: G.Havenith@lboro.ac.uk.
Abstract
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.
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.
Authors: Leonidas G Ioannou; Josh Foster; Nathan B Morris; Jacob F Piil; George Havenith; Igor B Mekjavic; Glen P Kenny; Lars Nybo; Andreas D Flouris Journal: Temperature (Austin) Date: 2022-04-26
Authors: Josh Foster; James W Smallcombe; Simon Hodder; Ollie Jay; Andreas D Flouris; Lars Nybo; George Havenith Journal: Int J Biometeorol Date: 2021-03-05 Impact factor: 3.787
Authors: Josh Foster; James W Smallcombe; Simon Hodder; Ollie Jay; Andreas D Flouris; George Havenith Journal: Int J Biometeorol Date: 2021-11-06 Impact factor: 3.787
Authors: Leonidas G Ioannou; Lydia Tsoutsoubi; Konstantinos Mantzios; Maria Vliora; Eleni Nintou; Jacob F Piil; Sean R Notley; Petros C Dinas; George A Gourzoulidis; George Havenith; Matt Brearley; Igor B Mekjavic; Glen P Kenny; Lars Nybo; Andreas D Flouris Journal: Temperature (Austin) Date: 2022-04-01