Marathons can be bad for your health, scientists have warned after a study found 80 percent of competitors suffer kidney injury because of dehydration.

科学家警告称，马拉松可能会对人体产生危害。他们的研究发现，由于缺水，百分之八十的马拉松比赛选手都患有肾功能损伤。

Researchers said that although the kidneys of the participants in the 26.2 mile race fully recovered within two days, their findings raise questions concerning the potential long-term impact at a time when marathons are increasing in popularity.

The findings were published by the American Journal of Kidney Diseases, as thousands of people prepare for next month's London Marathon.

Previous research has shown that engaging in unusually vigorous activities - such as military training - in warm climates can damage the kidneys, but little is known about the effects of marathon running.

A team of researchers led by Professor Chirag Parikh, of Yale University in the US, studied a small group of participants in the 2015 Hartford Marathon.

They collected blood and urine samples before and after the event. They analysed a variety of markers of kidney injury, including serum creatinine levels, kidney cells on microscopy, and proteins in urine.

The researchers found that 82 percent of the runners that were studied showed Stage 1 Acute Kidney Injury (AKI) soon after the race. AKI is a condition in which the kidneys fail to filter waste from the blood.

Prof Parikh said: "The kidney responds to the physical stress of marathon running as if it's injured, in a way that's similar to what happens in hospitalised patients when the kidney is affected by medical and surgical complications."

The researchers stated that potential causes of the marathon-related kidney damage could be the sustained rise in core body temperature, dehydration, or decreased blood flow to the kidneys that occur during a marathon.

While the measured kidney injury resolved within two days of running the marathon, the researchers said the study still raises questions about the effects of repeated strenuousactivity over time, especially in warm climates.

1 dehydration

n.脱水，干燥

参考例句：

He died from severe dehydration.他死于严重脱水。

The eyes are often retracted from dehydration.眼睛常因脱水而凹陷。

2 fully

adv.完全地，全部地，彻底地;充分地

参考例句：

The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气，然后全部呼出。

They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。

3 serum

n.浆液，血清，乳浆

参考例句：

The serum is available to the general public.一般公众均可获得血清。

Untreated serum contains a set of 11 proteins called complement.未经处理的血清含有一组蛋白质，共11种，称为补体。

4 affected

adj.不自然的，假装的

参考例句：

She showed an affected interest in our subject.她假装对我们的课题感到兴趣。

His manners are affected.他的态度不自然。

5 surgical

adj.外科的，外科医生的，手术上的

参考例句：

He performs the surgical operations at the Red Cross Hospital.他在红十字会医院做外科手术。

All surgical instruments must be sterilised before use.所有的外科手术器械在使用之前，必须消毒。

6 strenuous

adj.奋发的，使劲的;紧张的;热烈的，狂热的

参考例句：

He made strenuous efforts to improve his reading. 他奋发努力提高阅读能力。

You may run yourself down in this strenuous week.你可能会在这紧张的一周透支掉自己。