WE AREN'T MEANT TO WORK WITH JUST THE BODY OR THE BRAIN
The brain is a complex organ with many regions designed to collaborate with one another.
Depending on the kind of function necessary, different circuits talk to one another. These different functions might include swinging an ax, or filling out paper work.
When we do the latter, we're not moving much and that engenders a 'very different kind of fatigue than working in the garden,' says Dr Lieberman.
While physical tiredness can help us fall asleep at night, mental fatigue can actually do the opposite, making it harder to fall asleep and stay asleep.
This is because you are 'not using your mind and body the way they evolved to be used,' Dr Lieberman says.
'We evolved to strike a balance and for our brains and bodies to work together. At a desk job, we are utterly sedentary and only using our brains. This creates a chemical imbalance that makes us less efficient at processing energy, making us drained and tired.'
Evolution informs a lot of what makes us tired at work, according to Dr Lieberman.
Our wild brain thinks in terms of two categories: the resources we have and the ones we don't.
Resources we have are tangible through our senses. Similarly, physical work or work that combines physical and mental effort typically has a more tangible pay-off, a thing you can see you'e made or altered.
'For resources we don't have, but need, we have to focus on the possible and the future, and that includes abstract thinking,' Dr Lieberman explains.
'If you feel like having a peach, you have that idea in your imagination, in order to make it reality you need to be motivated, and plan how to get it and all of this is using the brain circuits to get what you don't have.
'In modern life, those circuits' - the same ones that we would operate on if we were starving - 'are the ones we rely on all the time.'
WE ONLY HAVE SO MUCH WILL POWER
'Will power is not an inexhaustible resource,' says Dr Lieberman.
A classic psychological experiment neatly illustrates his point.
Researchers placed a plate of freshly-baked cookies in a room with their study participants and told them they were not allowed to eat them.
Then they assigned them tasks to do, but 'people ran out of steam very quickly because they had already used all their willpower resisting cookies,' Dr Lieberman says.
'When you're sitting at your desk, constantly forcing yourself to do a task that you're not inclined to do, it's going to be very draining.'
IT'S IN THE AIR: OFFICE ENVIRONMENTS ARE DESIGNED TO EXHAUST US
A growing body of research demonstrates that sitting in an office all day is bad for us in all sorts of ways. Recently, several studies have also shown that the higher concentrations of CO2 in office environments make it harder to concentrate.
Dr Lieberman says that's just one a of 'a lot of bad things about the office environment: indoor pollution, rugs and upholstery that give off formaldehyde and other nasty things, and the lights aren't so good.'
He says that fluorescent lights confuse the body and our sense of night, day and time.
'Artificial light confuses the body, and we are most energized when our bodies are in sync with our daily rhythms,' Dr Lieberman explains.
He suggests offsetting the bad environment with a desk plant to purify the air and periodic strolls to the window to see some nature - a tangible sensory view that makes us turn off our abstract brains for a moment.
Plus, those strolls give you an opportunity to socialize, whereas most of the work day is 'socially isolating,' says Dr Liebrman.
'When we socialize, our brains release oxytocin, and it's an unanswered question about whether socializing online has the same effects, but Facebook and Instagram tend to have the opposite effect.'
KEEP IT TOGETHER: TASK-SWITCHING IS TIRING
Saying the ABCs as fast as you can is easy. Counting to 10 as fast as you can is easy. Now try alternating the two ('A, 1, B, 2, C, 3 ...' and so on).
'You'll tire out quickly,' Dr Lieberman says.
'Studies shave shown that the human brain can't really multi-task; you wind up switching your brain back and forth, and that's going to be more tiring than it would be if you did one thing and then you did the other.'
But that's not how most desk jobs work.
'Maybe you spend 10 to 15 minutes going through your emails, then you work on a report for 20 minutes, then you rush off to a meeting and come back and write notes ... you're constantly task-switching.'
But don't forget to make the healthy task-switch occasionally.
'When you take a break from all that abstract work your'e doing on the computer and just live in the present moment, you're creating a balance in the mind tht will be a huge relief to your brain,' says Dr Lieberman.
'People that have a desk job work in the unreal world of the abstract, and at the end of the day, you don't have a lot to show for that, so at the beginning of the day, list the tasks you have to accomplish, so at least you can draw a line through that task and feel a little satisfaction.
'You want to balance that with the concrete, to find ways to give yourself a sense of accomplishment at the end of the day.'
