The consequence? Stress, burnout, and eventually sickness - sometimes very severe and long-lasting.
Without exception, every person I've challenged on this has agreed that when they push through down cycles of tiredness, thinking perhaps that they're being lazy or that it's not 'ok' to slow down for a short while, they become less effective in the afternoon and end up dragging their weary bodies home at the end of the day - not much use to themselves or loving family waiting for their share of time.
So what to do about it? Morning and afternoon tea breaks and a lunch break away from your desk - they're some of the simple solutions. And what about Winston Churchill's famous technique - the one that kept him operating at full steam through all those tough war years? He was famous for his power naps. When tired he'd pop upstairs (when he was working at Downing Street) and hop into bed for about 20 minutes.
'But I work in a corporate environment and can't take a nap', you might be saying. Really? If you take the time to notice the messages your body sends you, and if you can show your employer or colleagues the benefits they reap from your increased effectiveness in the afternoon, you might be surprised how much support you get. It's not uncommon in some countries, including China, to see people napping at their desks after lunch. And what about the famous continental siesta?
For example, a young accountant in a large Auckland office, with full knowledge of his colleagues, often takes a 20 minute nap at his desk in the early afternoon. If he's really tired he even shuts the door (he's lucky enough to have one!) and lies down on the floor. After about 20 minutes he comes to, feels a little dozy for a couple of minutes, and then he's away - operating at far higher efficiency for the rest of the day than if he'd tried to push through the exhaustion zone.
Maybe you don't have the luxury of a door, but there are other solutions such as going to your car in the car park, maybe a sick room, or perhaps there's a quiet room you can use. Some firms have rooms dedicated to meditation or quiet relaxation - the only rule is no talking.
Not only will employers get higher productivity by making it appropriate for people to slow down but fewer mistakes will happen.
Signs that you need an Ultradian break? Your body will tell you - tiredness, yawning, irritability, mistakes (especially when you're at a keyboard), thirsty, unfocused, and sometimes aching parts - often the back.
So, employers, don't wait for the government to force you to be more profitable and have happier staff. Get the benefit now!
Robyn Pearce (known as the Time Queen) runs an international time management and productivity business, based in New Zealand. Get your free report 'How To Master Time In Only 90 Seconds' and ongoing time tips at gettingagrip.com.