Researchers quantify the impact of heat exposure on physical work capacity

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

Researchers at Loughborough University, led by Professor George Havenith, Director of the Environmental Ergonomics Research Center (EERC), investigated the impact of heat exposure on physical work capacity in the context of international HEAT-SHIELD project.

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

In their latest research paper, the EERC team investigates the interactions between working time and the severity of heat stress.

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

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

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

The research team found that in addition to the reduction already observed in previous one-hour trials, during the simulated shift, work output per cycle decreased even more, even in the cool climate, with the biggest reduction after the lunch break. and meal consumption.

In addition to the heat-induced reductions seen in the short one-hour trials (30, 45, and 60% for all three climates), compared to cool-climate work performance, there were on average 5%, 7% , and a 16% decrease in PWC when working a full shift for moderate, hot, and very hot conditions, respectively. Overall, this equates to a 35% drop in productivity throughout the working day when operating at temperatures of 35°C/50% RH, up to 76% when the thermometer reaches 40°C/70% relative humidity.

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 oppressive heat.

“A significant drop in productivity will have a significant impact on employee well-being and business output. This is further evidence of why action must be taken now to stop global warming, the effects of which are already felt the hardest by the countries of the South..”


Journal reference:

Smallcombe, J.W. et al. (2022) Quantification of the impact of heat on human physical work capacity; part IV: interactions between the duration of work and the severity of heat stress. International Journal of Biometeorology.

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