Researchers are quantifying the effects of heat exposure on physical performance

Researchers are quantifying the effects of heat exposure on physical performance

It is predicted that the planet's average temperature in 2100 could be between 2 and 9.7 °F (1.1 to 5.4 °C) warmer than today. But what impact would this rise in temperature have on the global workforce?

Researchers at Loughborough University, led by Professor George Havenith, Director of the Environmental Ergonomics Research Center (EERC), have investigated the effects of heat exposure on physical performance as part of the international HEAT-SHIELD project.

The Horizon 2020 study examines the negative impact of increased workplace heat stress on the health and productivity of five strategic European industries: manufacturing, construction, transport, tourism and agriculture.

In its latest research, the EERC team examines the interactions between work duration and severity of heat stress.

Prior to this study, models examining the influence of high workplace temperatures on physical work capacity (PWC) were based on exposure times of one hour. In a world first, the Loughborough team examined the effects of heat stress on PWC during a fully simulated work shift, consisting of six one-hour work-rest cycles in the heat during a working day.

For the study, nine healthy men completed six 50-minute work sessions, separated by 10-minute rest intervals and an extended lunch break, on four different occasions: once in a cool environment (15°C/50% relative humidity) and three different combinations of air temperature and relative humidity (moderate, 35°C/50% relative humidity; hot, 40°C/50% relative humidity; and very hot, 40 °C/70% relative humidity). This range of hot temperatures and conditions covers those already experienced by more than a billion workers around the world.

To mimic moderate to heavy exercise, work was performed on a treadmill at a fixed heart rate of 130 beats per minute. During each industrial action, PWC was quantified as the energy expended above resting levels.

The research team found that in addition to the reduction already observed in the previous 1-hour experiments, work output per cycle decreased even further over the course of the simulated shift, even in the cool climate, with the largest reduction occurring after lunch break and food consumption.

In addition to the heat reductions observed in the short 1-hour experiments (30, 45, and 60% for the three climate zones) relative to cool climate work performance, there were, on average, an additional 5%, 7%, and 16% decrease in PWC when work was performed over a full work shift for temperate, hot, and very hot conditions, respectively. Overall, this equates to a 35% loss in productivity during the workday at temperatures of 35°C/50% RH and a 76% drop when the thermometer reaches 40°C/70% RH.

Speaking about the study, Professor Havenith said: “These results improve our current understanding of the consequences of prolonged occupational heat exposure and provide evidence that can be used to more accurately predict the socio-economic burden of future extreme heat.

"Significant declines in productivity will have a significant impact on employee well-being and business performance. This is further evidence of why action should be taken now to stop global warming, the effects of which are already being felt most acutely by people in the Global South."

Source:

Loughborough University

Reference:

Smallcombe, JW, et al. (2022) Quantifying the effects of heat on human physical work ability; Part IV: Interactions between work duration and severity of heat stress. International Journal of Biometeorology. doi.org/10.1007/s00484-022-02370-7.

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