A week of total rest, even months after the injury occurred, still had benefits, according to the report in the Journal of Pediatrics.

"That's really important because very often we see patients with post-concussion syndrome months after" their concussion, said Rosemarie Moser, director of the Sports Concussion Center of New Jersey and lead author of the study.

Post-concussion syndrome involves headaches, mental fogginess, fatigue, and difficulty concentrating or sleeping, among other symptoms.

Typically, rest is the main treatment that clinicians offer patients, "but it's not systematic or comprehensive," said Moser. "Currently, it really varies as to how practitioners define cognitive and physical rest."

That's because there isn't a lot of evidence showing what types of rest are most helpful, she added.

To measure how well an intensive bout of rest can help athletes heal after a concussion, Moser's group ordered 49 high school- and college-age patients to rest for a full week.

The prescription was strict: the study participants could not go to school or work, talk on the phone, exercise, watch TV, socialize or work at a computer.

Moser said that, based on the parents' reports, most of the athletes were pretty good about sticking to the plan.

Fourteen of the patients started the rest within a week of their injuries. Another 22 patients began resting within a month of the concussion, and 13 patients began the week of rest between one and seven months after the concussion.

At the beginning of the study, all of the patients had symptoms related to the injury, such as headaches and trouble concentrating.

After the week of rest, all groups saw their symptoms improve.

Among the athletes who started the rest within a week of their concussion, their symptoms improved from a score of 22 on a 132-point scale down to seven.

Similarly, among those who began the week of rest more than a month out from their injury, symptoms dropped by 20 points, from 28 to 8.

"All of those symptoms improved dramatically. Qualitatively, you feel better," Moser said.

Moser's group also had the participants take mental tests -- which measured memory, processing speed and reaction time -- before and after the prescribed resting period.

The patients did better on all of the mental exams after they rested.

For instance, on a test of visual memory, people who started the rest within a week of the concussion or more than a month after the concussion had 10-percent better scores after their rest period, compared to before.

Such improvements are not immediately translatable to real life situations, Moser said, but better memory and mental speed might help someone during tasks like taking notes while listening to a teacher in school or remembering what a person just read.

Moser's group did not compare the participants' improvement to other people with concussions who got no special rest period, or who got some rest but less than the total cognitive and body rest imposed in the study.

So, at most, the report demonstrates that the rest did little harm and might have provided a benefit.

The study "provides some evidence to back up a recommendation that's already out there," said Dr. Willem Meeuwisse, a professor at the University of Calgary and a physician specializing in sports injuries who was not involved in the new work.

Meeuwisse told Reuters Health it's not clear whether the rest needs to be as intensive as it was in the study to deliver benefits.

He said that in typical practice, "we back off physical and cognitive activity until your symptoms improve and avoid things that provoke and make your symptoms worse. That's ideal because then you can individualize."

SOURCE: bit.ly/LIzgv7 Journal of Pediatrics, online May 24, 2012.

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