All athletes are familiar with that cramping feeling after a tough session.
It can strike particularly ferociously after a workout in hot summer conditions.
That’s because excessive sweating can make muscle cramps much worse, so elite athletes make it a priority to get fluids back in after training.
It’s long been a debate as to whether they should be drinking plain mineral water or an electrolyte drink.
People usually have strong views as to whether these drinks are actually better than water, or whether the hype is just clever marketing.
But research released this year suggests it is worth substituting H2O.
"Many people think dehydration causes muscle cramps and will drink pure water while exercising to prevent cramping," the lead researcher of the study said
"We found that people who solely drink plain water before and after exercise could in fact be making them more prone to cramps.
"This is likely because pure water dilutes the electrolyte concentration in our bodies and doesn't replace what is lost during sweating."
The researchers followed 10 men who ran in the heat for 40-60 minutes and took either an electrolyte beverage or pure water,
They then repeated the test with the other drink a week later.
Scientists used electrical stimulation on the leg muscles to induce cramping. They also took blood samples to compare electrolyte levels in the runners.
The electrolyte beverage made runners less susceptible to cramping.
Concentrations of sodium and chloride decreased immediately after the run among the plain water drinkers but they did not for those taking the electrolyte drink.
"Electrolytes are vital to good health -- they help the body to absorb water more effectively than plain water and replace essential minerals lost through sweat or illness," he said.
"People should consider drinking oral rehydration fluids instead of plain water during moderate to intense exercise, when it's very hot or when you are sick from diarrhoea or vomiting."