- Efficiency in simple tasks (cross out every letter T in a sheet of newsprint) varies with body temperature.
- Memory and verbal reasoning varies with a clock of c. 21 hours.
- Routine repetitive manual tasks (pegs into holes) more successful late afternoon or early morning.
- Brain challenging tasks better late morning or midday.
- Long term memory peaks late in day, short term memory peaks around 10am to 11am.
- Flying from east to west shortens the day; flying from east to west lengthens the day nearer to natural rhythm.
- Tendency to clumsiness and duller mentally; wits recover sooner than dexterity.
- Travellers who stay in hotel rooms take longer to recover than those who go out and meet people.
- Changing shift work schedules: digestion realigns with new sleep/wake cycle relatively quickly; temperature rhythm is next; last is cell division rhythm.
- Worst shift patterns are 12 hour shifts and highly variable ones.
- Workers adapt more easily to later working hours.
- Human rhythms can be changed by changing the meal schedule, with one meal a day. Only breakfast - insulin peaks c. 10am, glucagen c. 11 am, blood iron just before meal. Only dinner, insulin peaks c. 6pm, glucagen c. 11pm, blood iron just before meal.
- Greatest risk of accidents in the two hours before dawn - body temperature and alertness is at its lowest at around 5am.
- Biological clock needs daylight brightness level (10,000 lux on overcast day) to reset each day (candle = 20 lux, electric lamp = 300 lux).
Jeremy Campbell: Winston Churchill's Afternoon Nap.
BBC2 Horizon: Against the clock, broadcast 2 April 1994.
