In a study led by a sleep expert at the University Of Pennsylvania School Of Medicine, participants were restricted to just four hours’ sleep for five nights and then given a “recovery” sleep of 10 hours. Even after this sleep their reaction times, attention span and levels of fatigue failed to return to normal, showing that a single weekend may not be sufficient to make up for the lack of sleep during the week.

Source – https://www.realbuzz.com/articles/10-health-myths-busted/