IT’S 10am and you are buzzing with efficiency, dealing with phone calls and effortlessly taking notes, writes Liz Hollis. But after lunch your productivity plummets. You ride out the energy dip and by mid-afternoon you are just about back on form.

The fluctuations are caused by our internal body clocks, which trigger changes in our mood, hormones, immune system and body temperature through a 24-hour cycle.

Chronobiologists — scientists of the body clock — believe that understanding how it functions could help you to plan the way you work.

Simon Folkard, professor at the Body Rhythms Centre, University of Wales, Swansea, says: “The body clock means that our efficiency at performing tasks varies over the day. For example, mem-ory performance changes. Short-term memory is best early in the morning. However, long-term memory is best later in the day. There seems to be a time-linked effect in any activity.”

The scientists say intellectual tasks are best dealt with between 10am and noon. Important decisions are best made when judgment is most balanced, at noon, also the best time for anything stressful, such as dealing with difficult people. After lunch, in the post-prandial dip, schedule routine tasks that you can do without thinking too much.

Around mid-afternoon our mental activity surges again, although to a lower level than in mid-morning. Physical strength peaks at 4pm — this is when most Olympic records are set.

With research into the body clock advancing, we will soon learn more about how to plan our working day for maximum efficiency. But Professor Folkard cautions that there may be individual variations in how our clocks run. And then of course, there are those bosses who couldn’t care less about your body clock and insist on giving you taxing mental tasks at 2.30pm during your post-prandial dip.

But what do PAs think? Jordan Jenner, PA to the managing director at the TV company Imago Productions, says: “I tend to do intellectually taxing jobs before lunch and save routine tasks for the afternoon. I also send important e-mails first thing, so that the recipients can tackle them before lunch when they too are at their best. Send them later and they are less likely to be acted upon.”

Eva Smith, PA to the vice-president at Cable & Wireless, says: “I like to do all my important jobs in the morning. However, there are many times when sheer pressure of work means you have to override your body clock. Just after lunch may not be the best time for a meeting or intellectual tasks, but sometimes there is no option.”

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