Loughborough University
Browse

Quantifying the impact of heat on human physical work capacity; part III: the impact of solar radiation varies with air temperature, humidity, and clothing coverage

Download (3.79 MB)
journal contribution
posted on 2021-10-29, 08:23 authored by Josh Foster, James W Smallcombe, Simon HodderSimon Hodder, Ollie Jay, Andreas D Flouris, Lars Nybo, George HavenithGeorge Havenith
AbstractHeat stress decreases human physical work capacity (PWC), but the extent to which solar radiation (SOLAR) compounds this response is not well understood. This study empirically quantified how SOLAR impacts PWC in the heat, considering wide, but controlled, variations in air temperature, humidity, and clothing coverage. We also provide correction equations so PWC can be quantified outdoors using heat stress indices that do not ordinarily account for SOLAR (including the Heat Stress Index, Humidex, and Wet-Bulb Temperature). Fourteen young adult males (7 donning a work coverall, 7 with shorts and trainers) walked for 1 h at a fixed heart rate of 130 beats∙min−1, in seven combinations of air temperature (25 to 45°C) and relative humidity (20 or 80%), with and without SOLAR (800 W/m2 from solar lamps). Cumulative energy expenditure in the heat, relative to the work achieved in a cool reference condition, was used to determine PWC%. Skin temperature was the primary determinant of PWC in the heat. In dry climates with exposed skin (0.3 Clo), SOLAR caused PWC to decrease exponentially with rising air temperature, whereas work coveralls (0.9 Clo) negated this effect. In humid conditions, the SOLAR-induced reduction in PWC was consistent and linear across all levels of air temperature and clothing conditions. Wet-Bulb Globe Temperature and the Universal Thermal Climate Index represented SOLAR correctly and did not require a correction factor. For the Heat Stress Index, Humidex, and Wet-Bulb Temperature, correction factors are provided enabling forecasting of heat effects on work productivity.

Funding

“HEAT-SHIELD,” European Union’s Horizon 2020 research and innovation program under grant agreement no. 668786

History

School

  • Design and Creative Arts

Department

  • Design

Published in

International Journal of Biometeorology

Volume

66

Pages

175-188

Publisher

Springer Science and Business Media LLC

Version

  • VoR (Version of Record)

Rights holder

© The authors

Publisher statement

This is an Open Access Article. It is published by Springer under the Creative Commons Attribution 4.0 Unported Licence (CC BY). Full details of this licence are available at: http://creativecommons.org/licenses/by/4.0/

Acceptance date

2021-10-07

Publication date

2021-10-28

Copyright date

2022

ISSN

0020-7128

eISSN

1432-1254

Language

  • en

Depositor

Prof George Havenith . Deposit date: 28 October 2021