Sleep

Our Bodly Clock is reset daily by zeitgebers. The most influencial is light. But with shift work the zeitgebers will be at opposite ends. EG: Evening 'sounds' will come at the start of their day and dawn will bring it to a close. Body tempreture is near fixed and takes a long time to change it.

However not all will have the same problems Because as ....

WEBB (1975) : Showed that some people are more alert in the mornings than the afternoon. In fact some work naturally more at night .... One example that could be included is students who work all night on essays.

Phase delay is best.

Occurs when you have to get up later than normal, and go to bed later. Whereas its much harder to get up earlier and go to bed earlier.

East to west is best. ------- LINK TO JET LAG

All biological rhythms, including circadian rhythms, fluctuate between high and low values during a specified interval of time. The largest values are called "peaks", while the corresponding lowest values are called "troughs."

Alertness / Tempreture drop to their lowest at about 4-6 am.

Hence this is the time when most accident occur.

Suggested a US company used a phase delay system and make shift changes every 21 days rather than 7. To give staff time to adjust.

After 9 months worker satisfaction and out put increased.

Investigated the effect of light in order to improve adjustment to night shifts. One group of workers was exposed to bright light and total darkness during the days. whilst the other group had normal lighting and slept at home during the day.

After 6 days the 1st groups circadian rhythm was completly entrained whereas the control group had little or no adjustment.