Drinking water after exercise likely to cause painful muscle cramps
Australian researchers gave exhausted men different types of drinks and zapped them with electricity to test how well they withstood leg cramps.
Researchers at Edith Cowan University in Perth made 10 men run on a treadmill in a hot room until they sweated out two per cent of their body weight.
When they finished, half the men were given normal water to rehydrate, while the other half were given sports drinks with electrolytes in.
Electrolytes are minerals in the blood, which include salt, potassium, bicarbonate and chloride – they are depleted when people sweat during exercise.
A week later the same experiment was repeated and the men had the drink they weren’t given the first time.
‘There have been many theories proposed as to what causes muscle cramps in the past,’ said Professor Ken Nosaka, study author.
‘But this is the first time that we have conclusively shown that electrolyte depletion is the primary cause of muscle cramps.’
Professor Nosaka and his team found men who drank pure water became more likely to experience muscle cramp.
Whereas those who were given the electrolyte drinks had a ‘significantly reduced’ likelihood of the painful experience.
They tested each volunteer’s susceptibility to cramp by channeling an electric current into their calf muscle.
The less electricity needed to trigger the muscle spasm, the more susceptible they were – and the water-drinkers responded to weaker currents than the other men.
‘When we exercise, we sweat out fluid that contains electrolytes,’ said Professor Nosaka.
‘So when we replace this lost fluid with pure water, we are actually diluting the electrolytes in our system which causes muscle cramp.’
The team’s research stopped short of explaining how lower numbers of electrolytes could trigger the cramps.
But this could be down to the minerals’ role as nerve signal transmitters – fewer of them may reduce the body’s ability to properly regulate muscle contractions.
Professor Nosaka now plans to do a follow-up study to work out whether consuming electrolytes could prevent cramp.
The research was published in the journal BMJ Open Sport & Exercise Medicine.