Image caption The true value of sleep is often overlooked, researchers say

The value of sleep has been reinforced by yet another scientific study.

Research published in the journal Sleep suggests that sleeping longer can markedly improve physical performance.

When Stanford University's male basketball team was asked to sleep for 10 hours a night for around six weeks, their shooting accuracy improved by 9%.

The study at the US university found that getting enough sleep and rest was as important as training and diet for elite athletes.

Cheri Mah, researcher at the Stanford Sleep Disorders Clinic and Research Laboratory, who worked with the basketball players, said that sleep was often overlooked.

"Intuitively many players and coaches know that rest and sleep are important, but it is often the first to be sacrificed," she said.

The researchers asked the players to maintain their normal night-time schedule (sleeping for six to nine hours) for two-to-four weeks and then aim to sleep 10 hours each night for the next five-to-seven weeks.

Many athletes testified that a focus on sleep was beneficial to their training and performance. Cheri Mah, Stanford University

During the study period, players stopped drinking coffee and alcohol. They were also asked to take daytime naps when travel prevented them from getting 10 hours of night-time sleep.

The study found that the players ran faster timed sprints (16.2 seconds at the start of the study compared with 15.5 seconds at the end), their shooting accuracy improved by 9% and their fatigue levels decreased.

The athletes also reported improved performance during competitive basketball games.

The findings suggest that it is important for sleep to be prioritised over a long period of time, not just the night before match-day, Mah says.

Sleep debt

She called optimal sleep an "unrecognised, but likely critical factor in reaching peak performance".

She said the findings may be applicable to recreational athletes as well as those performing at school or at a higher level.

Before the study began, Mah and colleagues also discovered that many of the athletes felt sleepy during the day.

This indicated that they were carrying sleep debt accumulated from chronic sleep loss, she said.

"The athletes were unaware that it could be negatively impacting their performance.

"But as the season wore on and they reduced their sleep debt, many athletes testified that a focus on sleep was beneficial to their training and performance."

Derk-Jan Dijk, professor of sleep and physiology at the University of Surrey, said we should look at sleep in the same way as exercise.

"We should look at sleep as an active process. Getting enough sleep is a positive thing which will help you perform in all aspects of life.

"It may be that extra sleep leads to more effective training routines and helps us learn patterns better. Practice makes perfect - and that happens more quickly if you get enough sleep."