Apprentice tradies in northern Australia will swallow capsule thermometers to track their core body temperature during work hours as part of a range of studies to address productivity lost through heat stress in the tropics.

A 2015 study found that heat stress cost the Australian economy $6.2bn in lost productivity and suggested that temperature increases due to climate change would cause productivity to decrease by up to 20% globally during summer months by 2050.

Dr Elspeth Oppermann, coordinator of the Heat Stress Research Partnership and a co-author of the 2015 study, said she believed the productivity loss was already greater than estimated in the tropical zone of northern Australia, where “unbearable” conditions persist for months.

The research partnership aimed to study how local workers and workplaces adapted to working in extreme heat and humidity, particularly for outdoor workers, and develop appropriate heat stress management practices.

It also aimed to track differences in physiological responses to extreme heat, which is where the thermometers come in.

“What we ask them to do is swallow these little capsules that contain a gastro-intestinal thermometer that transmits people’s temperatures in real time over the course of a work shift,” Oppermann told Guardian Australia.

“What’s of interest to us is how people work in these conditions. What we can do by observing their temperatures is see how their particular mode of working affects their core body temperatures.”

Oppermann said the dual factors of climate change and federal government plans to develop northern Australia added urgency to the need to understand how to manage heat stress.

She said health and safety guidelines for heat stress, which recommend stopping work if the temperature reaches 35C or 28C with 70% humidity, were not appropriate for the tropical zone, which spans the northern coastline from Broome to Townsville.

“It’s very, very difficult for employers and employees because if they were to do that they would stop work very, very frequently,” she said.

Recommended cooling practices for the dry heat of southern Australia, such as laying a wet flannel on your head or sitting in the shade, also don’t work in areas of high humidity such as Darwin or Broome.

Instead, people need to do “active cooling” – taking a break inside an air-conditioned space, crunching ice or even sinking into an icy bath – to cool their core body temperature.

Oppermann said the symptoms of heat stress, such as headaches, irritability and a “heat hangover”, were accepted as commonplace by many people working in northern Australia during the build-up to the wet season, from October to December, and one in four workers surveyed said they experienced the symptoms of heat stress once a week.

That’s exacerbated in some workplaces by “a macho culture of pushing through”.

“People would often expect to feel headaches and irritability, and going home and just going to bed is a really common story,” she said.

Others turn to alcohol, which makes matters worse by increasing dehydration.

“Everyone knows anecdotally that people drink more when it’s hot,” she said. “It’s a response that’s understandable if your body feels exhausted because of heat stress.”

The partnership is a joint project between group training organisations in the Kimberley, Northern Territory and far north Queensland, and researchers at Charles Darwin University, the Menzies School of Health Research, James Cook University and the Centre for Urban Research at RMIT.