The restoration theory of sleep function is carried out by Oswald, who argues that the purpose of sleep is to restore depleted energy reserves, eliminate waste products from muscles, repair cells and recover physical abilities that have been lost during the day. Evidence for this theory is firstly by Shapiro, who found that people who ran an ultra marathon slept 1.5 hours longer then they did two nights following the race. In addition, stage four occupied …showed first 75 words of 464 total…

…showed last 75 words of 464 total…result of the increased nerve cell activity is unknown. Also REM sleep uses a substantial amount of energy and it has been argued that this would prevent high levels of protein synthesis. This then shows that the answer is unknown and the result is inconclusive. This is criticised by the evolutionary theory has it suggests that the reason for sleep is adaptive for survival and reproduction but this states that sleep is designed for restoration.