【Weallknowthatthenormalhumandailycycleofactivityisofsome7-8hours'sleepalternating(交替)withsome16-17hours'wakefulnessandthatthesleepnormallycoincideswiththehoursofdarkness.Ourpresentconcerniswithhoweas】

　　Weallknowthatthenormalhumandailycycleofactivityisofsome7-8hours'sleepalternating(交替)withsome16-17hours'wakefulnessandthatthesleepnormallycoincideswiththehoursofdarkness.Ourpresentconcerniswithhoweasilyandtowhatextentthiscyclecanbemodified.

　　Thequestionisnomereacademicone.Theeaseforexamplewithwhichpeoplecanchangefromworkinginthedaytoworkingatnightisaquestionofgrowingimportanceinindustrywhereautomationcallsforround-the-clockworkingofmachines.Itnormallytakesfromfivedaystooneweekforapersontoadapttoareversed（颠倒的）routineofsleepandwakefulnesssleepingduringthedayandworkingatnight.Unfortunatelyitisoftenthecaseinindustrythatshifts(轮班)arechangedeveryweek;apersonmayworkfrom12midnightto8a.m.oneweek8a.m.to4p.m.thenextand4p.m.to12midnightthethirdandsoon.Thismeansthatnosoonerhashegotusedtooneroutinethanhehastochangetoanothersothatmuchofhistimeisspentneitherworkingnorsleepingveryefficiently.

　　Theonlyrealsolutionappearstobetohandoverthenightshifttoanumberofpermanentnightworkers.Aninterestingstudyofthedomesticlifeandhealthofnight-shiftworkerswascarriedoutbyBrownin1957.Shefoundahighincidence(发生率)ofdisturbedsleepandotherdisordersamongthoseonalternatingdayandnightshiftsbutnoabnormaloccurrenceofthesephenomenaamongthoseonpermanentnightwork.

　　Thislattersystemthenappearstobethebestlong-termpolicybutmeanwhilesomethingmaybedonetorelievethepressureofalternatedayandnightworkbyselectingthosepeoplewhocanadaptmostquicklytothechangesofroutine.Onewayofknowingwhenapersonhasadaptedisbymeasuringhisbodytemperature.Peopleoccupiedinnormaldaytimeworkwillhaveahightemperatureduringthehoursofwakefulnessandalowoneatnight;whentheychangetonightworkthepatternwillonlygraduallygobacktomatchthenewroutineandthespeedwithwhichitdoessoparallelsbroadlyspeakingtheadaptationofthebodyasawholeparticularlyintermsofperformance.Thereforebytakingbodytemperatureattwo-hourintervals(间隔时间)throughouttheperiodofwakefulnessitcanbeseenhowquicklyapersoncanadapttoareversedroutineandthiscouldbeusedasabasisforsel