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It’s actually water cramping our style

Drinking water after exercise increases the risk of muscle cramps.

Far from preventing cramps, drinking water after exercise can actually cause them, according to new research from Edith Cowan University.

The study by researchers from ECU’s School of Medical and Health Science has debunked the idea that dehydration can produce muscle cramp, showing for the first time that the real cause of the painful contractions is a lack of electrolytes.

Stimulating cramps

Lead researcher Professor Ken Nosaka began researching what causes muscle cramps because he often suffered from them himself during and after playing tennis.

He designed an experiment in which 10 untrained men ran on a treadmill in a hot room until they had lost two per cent of their body weight through sweat.

Half were randomly chosen to be given a drink of pure water and the other half were given a drink of water containing electrolytes.

One week later the same men repeated the exercise, but were given the alternate drink to the first experiment.

An electrical stimulation was then applied to the participants’ calves to induce muscle cramp.

The lower the frequency of electrical stimulation required to induce muscle cramp, the more the person is susceptible to muscle cramp.

Diluting electrolytes

“What we found was that drinking pure water after exercise actually increased the susceptibility to muscle cramp,” Professor Nosaka said.

“Conversely, drinking fluid containing electrolytes significantly reduced the susceptibility to muscle cramps.”

Professor Nosaka said the likely reason drinking pure water puts us at a greater risk of cramping is because it dilutes the electrolytes already in the body fluid.

“When we exercise, we sweat out fluid that contains electrolytes. So when we replace this lost fluid with pure water, we are actually diluting the electrolytes in our system which causes muscle cramp,” he said.

World first research

Professor Nosaka said that this was the first study to show electrolyte depletion causing muscle cramps.

“We have long known that electrolytes are vital to muscle function, but this research shows that they are also the key to reducing or even preventing painful muscle cramps,” he said.

“There have been many theories proposed as to what causes muscle cramps in the past but this is the first time that we have conclusively shown that electrolyte depletion is the primary cause of muscle cramps.”

Professor Nosaka is planning a follow-up study to examine what concentration of electrolytes are needed to protect against muscle cramps after exercise, as well as how muscle cramps affect sleep for elderly and pregnant women.

‘Water Intake After Dehydration Makes Muscles More Susceptible to Cramp but Electrolytes Reverse that Effect’ will be published in BMJ Open Sport & Exercise Medicine on 5 March 2019.

World-ranked sports science

ECU has been ranked in the world's top 100 for Sports Science in the 2019 QS World University Rankings.

And our Sports Science program also ranked in the world's top 25 in the 2018 ShanghaiRanking global survey of Sports Science Schools and Departments.


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