Marathons can be bad for your health, scientists have warned after a study found 80 percent of participants suffered some form of kidney damage from dehydration.
The results were published by the American Journal of Kidney Diseases ahead of next month's London Marathon, for which thousands of people are preparing.
Previous research has shown that participating in unusually vigorous activities, such as military training, at higher temperatures can damage the kidneys, but there was no information on the effects of running marathons.
A team of researchers led by Professor Kirag Parik at Yale University studied a small group of participants in the 2015 Hartford Marathon. Blood and urine samples were taken from the competitors before and after the marathon and the level of serum creatinine, kidney cells and protein in the urine were analyzed.
They found that 82 percent of the runners were diagnosed with first-stage acute kidney injury soon after the race. It is a condition in which the kidneys do not filter waste from the blood.
"The kidney responds to physical exertion during marathon running as if it were injured, similar to what happens to hospitalized patients during medical and surgical complications," said Parik.
The researchers said that potential causes of kidney damage during a marathon could be a constant rise in temperature, dehydration or reduced blood flow to the kidneys.
"We need to investigate the effects of repeated strenuous activities, especially in warm regions," said Parik and added that the research also showed changes in the heart associated with marathon running, reports Klix.ba.
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