Athletes and soldiers who carry large amounts of water on long journeys to reimburse fluid loss due to sweating can now take it easy, for scientists now suggest that the volume of sweat they produce is much less than what is generally believed.
For a long time, soldiers and athletes have relied on an equation to predict how much water they will need to drink during long bouts of exercise, given the temperature and expected level of exertion
However, recent studies have defied the equation claiming that it over-estimates sweat volumes.
For further probing, Michael Sawka and colleagues, at the US Army Research Institute of Environmental Medicine, ran 101 volunteers through a gamut of exercises in a wide range of temperatures and humidity levels, both inside and outside.
They specifically monitored participants during eight hours of exercise, as compared to past measurements, which were taken after just two hours.
It was found that over time, people didn't simply keep producing more sweat.
On the other hand, volumes levelled out, perhaps because sweat glands were depleted.
Thus, the researchers concluded that the total perspiration over a long period was less than expected.
Sawka's team used the findings to create a new equation, which predicted sweat volume accurately 95 per cent of the time.
"There was a great need to improve that prediction equation, for both the military and public health and safety and disaster relief," New Scientist magazine quoted him as saying.
He added: "They make [the equation] quite user-friendly," said Ollie Jay, a professor of human kinetics at the University of Ottawa. "It's a very significant contribution to the field."
In fact, the researchers are now developing an iPhone application that would calculate personalised water needs for athletes.