A new study suggests that healthy adults who get at least eight hours of sleep a night may be less likely to experience common exercise-related injuries.

The study was based on information from over 7,500 United States soldiers in the Army's Special Operations Forces. About 95 percent of the study subjects were men.

The researchers found that soldiers who got no more than four to five hours of sleep a night were over two times as likely to report bone or muscle injury in the last year than those who slept eight hours or longer.

Tyson Grier is with the U.S. Army Public Health Center in Maryland. He was one of the writers of the study. He said that getting enough sleep not only improves physical performance among active people, but it "may also...have a positive impact on musculoskeletal injury prevention."

During the yearlong study, more than half of the soldiers said they had experienced at least one musculoskeletal injury.

Most study subjects – about 63 percent – reported getting six to seven hours of sleep a night. About 10 percent reported getting no more than four hours. Only 16 percent got eight hours or more.

Compared to those who reported eight hours of sleep or more each night, soldiers who slept seven hours were 24 percent more likely to experience a musculoskeletal injury.

The risk climbed as the hours of sleep dropped, with a 53-percent greater injury risk at six hours of sleep. At five hours of sleep, the risk of injury was two times greater.

In the Army, two-thirds of injuries are from musculoskeletal overuse. Most are caused by physical training or repetitive activities, the research team wrote in the study, which was published in Sleep Health.

About 42 percent of Army soldiers report an average of five hours of sleep or less each night. The study notes that making sure soldiers get enough rest could be a way to reduce injury risk.

One limitation of the study is that researchers depended on soldiers reporting how long they slept each night. And, additional research would be needed to test whether increasing sleep time really reduces injuries.

Dr. Hohui Wang is with the University of California, San Francisco. He was not involved in the study. He said that getting too little sleep leads to decreased attention and mental energy, which can lead to people being more likely to get hurt.

Wang added that sleep loss causes "cell damage in multiple organs." Getting extra sleep might help reverse this cell damage over time.

Most people are healthiest and perform their best with seven to nine hours of sleep a night, said Captain Jeffrey Osgood. He is with the Walter Reed Army Institute of Research in Maryland. He was not involved in the study.

Osgood offered suggestions for how people can get more – and better-quality – sleep.

He advises the following:

"Try to avoid caffeine, nicotine, and exercise in the hours leading up to sleep; avoid using alcohol as a sleep aid; don't go to bed hungry; try to keep your bedroom dark and quiet; use sleep masks and/or earplugs if needed; and keep your smartphone/devices out of bed."

I'm Ashley Thompson.

Lisa Rapaport reported this story for Reuters news agency. Ashley Thompson adapted it for VOA Learning English. Mario Ritter, Jr. was the editor.

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muscle –n. a body tissue that can contract and produce movement

positive –adj. good or useful

impact –n. a powerful or major influence or effect

musculoskeletal –adj. related to the muscular and skeletal systems of a human body

caffeine –n. a substance that is found especially in coffee and tea and that makes you feel more awake

nicotine –n. a poisonous substance in tobacco that makes it difficult for people to stop smoking cigarettes

mask –n. a covering for your face or for part of your face

earplugs –n. a piece of soft material that you put in your ear to keep out water, noise, etc.