People are being warned to "stop exercising" during the heatwave to avoid the risk of becoming seriously ill. The extreme weather adds to the large amount of warmth produced by the body during physical activity - increasing the likelihood of developing deadly heatstroke.
Mike Tipton, professor of human and applied physiology at the University of Portsmouth, said a person can go from emitting as much heat as a 90 watts lightbulb when at rest to giving off as much heat as a two kilowatt fire when exercising. He added: “We produce a lot of heat when we exercise.
“And we’re now at a temperature where… actually people will warm up, just doing their day-to-day activities in the house, or outside, and cooking, that sort of thing. And so fitter people undoubtedly do better in the heat, but we still see fit people who suffer from heat exhaustion in particular.
“So the recommendation would be just for the next couple of days, when we’re now in unprecedented temperatures, is just to stop exercising.”
The Met Office was forecasting temperatures could climb to 38C or even a record-breaking 39C on Monday. Wales has provisionally recorded its hottest day on record, with the temperature reaching 37.1C in Hawarden, Flintshire, beating the previous record for the country which has been in place since 1990.
Tuesday is predicted to be even hotter, with temperatures possibly reaching 41C in Yorkshire and Lincolnshire. The existing UK record, of 38.7C, was recorded in Cambridge in 2019.
Prof Tipton explained that people overheating through exercise risked putting “additional load on the health system”. And Dr Eunice Lo, climate scientist at the University of Bristol Cabot Institute for the Environment, said: “Everyone is at risk and we do need to be aware and take precautions and definitely not view these as normal summer days or something to go out and have fun in.”
Meanwhile researchers have also identified those with psychiatric illness as a group vulnerable to extreme temperatures. Dr Laurence Wainwright, departmental lecturer at the Smith School of Enterprise and the Environment, University of Oxford, said: “In recent years, there’s been an increasingly large body of research showing us that heatwaves worsen outcomes for those with underlying psychiatric illnesses – rates of suicides go up, levels of mortality go up, for those with existing conditions, symptoms can worsen.
“For people with certain conditions, say bipolar disorder, extreme heats can trigger people into certain aspects or certain phases for that condition. For bipolar, for instance, mania.”
He added: “A couple of nights of broken sleep can be a trigger for the onset of a depressive phase.”
Dr Wainwright said various medications for a number of treatments also have an impact as they may have an effect of hydration or thirst. He said: “There’s a lot we don’t know, but what is very clear is that heatwaves have implications for those with underlying medical conditions.”
