（湖南省长沙市一中2010届高三第九次月考B篇）Weallknowthatthenormalhumandailycycleofactivityisofsome7—8hours’sleepalternationwithsome16—17hours’wakefulnessandthatbroadlyspeakingthe

　　（湖南省长沙市一中2010届高三第九次月考B篇）

　　Weallknowthatthenormalhumandailycycleofactivityisofsome7—8hours’sleepalternationwithsome16—17hours’wakefulnessandthatbroadlyspeakingthesleepnormallycoincideswith(与一致)thehoursofdarkness.Ourpresentconcerniswithhoweasilyandtowhatextentthiscyclecanbemodified.

　　Thequestionisnomoreanacademicone.Theeaseforexamplewithwhichpeoplecanchangefromworkinginthedaytoworkingatnightisaquestionofgrowingimportanceinindustrywhereautomationcallsforround-the-clockworkingofmachines.Itnormallytakesfromfivedaystooneweekforapersontoadapttoareversedroutineofsleepandwakefulnesssleepingduringthedayandworkingatnight.Unfortunatelyitisoftenthecaseinindustrythatshiftsarechangedeveryweek;apersonmayworkfrom12midnightto8a.m.oneweek8a.m.to4p.m.thenextand4p.m.to12midnightthethirdandsoon.Thismeansthatnosoonerhashegotusedtooneroutinethanhehastochangetoanothersothatmuchofhistimeisspentneitherworkingnorsleepingveryefficiently.

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

　　Thislattersystemthenappearstobethebestlong-termpolicybutmeanwhilesomethingmaybedonetorelievethestrainsofalternativedayandnightworkbyselectingthosepeoplewhocanadaptmostlikelytothechangeofroutine.Onewayofknowingwhenapersonhasadoptedisbymeasuringhisbodytemperature.Peopleengagedinnormaldaytimeworkwillhaveahightemperatureduringthehoursofwakefulnessandalowoneatnight;whentheychangetonightworkthepatternwillonlygraduallygobacktomatchthenewroutineandthespeedwithwhichitdoessoparallelsbroadlyspeakingtheadaptationofthebodyasawholeparticularlyintermsofperformance.Thereforebytakingbodytemperatureatintervalsoftwohoursthroughouttheperiodofwakefulnessitcanbeseenhowquicklyapersoncanadapttoareversedr