The Cure to Mental Fatigue

Have you ever felt exhausted in the middle of day and when you got home you were so devoid of energy that all you could do was space out in front of the TV?[i]  It’s a common phenomenon in corporate life.  Yet, if you look at the problem closely the only physically taxing thing you probably did at work was type on your keyboard.  The rest of it was primarily mental.

How can mental exertion make you so tired? Is it possible that the two pound wonder called the brain is able to expend most of your physical energy simply through thinking?

Science says it’s not likely. Sitting at your desk performing cognitive functions doesn’t take much energy.  Your brain is remarkably energy efficient.  It only needs 12 watts of energy to operate smoothly, which is one-fifth the energy it takes to light up your desk lamp.  On top of that, the brain burns only 11 calories an hour, which is the equivalent of one minute of modest exertion on a sationary exercise bike. This is certainly not enough to exhaust a healthy human being.

So, is it the difficulty of a mental task or the amount of time you concentrate on the task that leaves you exhausted?

Science says this explaination is also unlikely.  Mental fatigue is really not about the task.  For example, millions of neurons connecting through a multitude of neural circuits are active when you follow a movie with dialogue and plots as complex as The Matrix or read War and Peace or play a game of mahjong.  Yet you can focus on these complex activities for two hours straight and still have the energy to get up and do something more with your day.  These kinds of intellectual activities can actually be stimulating.

So if the difficulty or duration of mental exertion doesn’t cause mental fatigue, what does?

It’s your mental attitude.  Science has found that if you believe a task is going to be difficult, it will be.  If you expect a meeting to drain your energy, it will. If you think of a task as stressful, it will activate your stress response system. Stress hormones will pour into your bloodstream.  They will drain your energy by elevating heart rate and blood pressure.  These hormones will dull and debilitate the higher brain function that sustains performance, further compounding the problem.  You’ll be more prone to emotional upsets, memory lapses, bad decisions and errors.  This will lead to more stress hormones burning up more energy, causing more emotional upsets and derailing more cognitive functions.  It becomes a pattern that supports the initial belief that the day was going to be difficult.  Here’s the point: The long exhausting day had little or nothing to do with the task and everything to do with your attitude.

So, is it hopeless?  Science says no.  We may not control our to-do list but we do have control over our to-be. Our attitude relates to how we want to be as we do what we have to do.  Attitude is the inner dimension of consciousness that makes you larger than circumstances, instead of an exhausted victim of circumstances.  You can start building this capacity in the boot camp of ordinary life.  Practice shifting your attitude in a situation as innocuous as standing in line.  For the next two couple weeks, whenever you go to the store, choose to stand in the longest line. Allow yourself to be aware of all the unpleasant thoughts you think and how you feel as you watch other people in shorter lines or how annoyed you become with someone who slows-up the check-out process. Then practice consciously shifting your attitude by letting go of the upset and being at peace, enjoying the moment exactly as it is.  Imagine you’re building the muscle in your brain that empowers a positive attitude to face any situation. Then translate what you learn from standing in line into reframing more challenging problems, like doing a budget or attending a boring meeting.

After two weeks of practicing in long lines, you can take the process a step further by using a guided process called PreAttitude.  It reframes your attitude around a task you consider boring, tedious, irritating, stressful or even frightening.


Ferris Jabr, ‘Does Thinking Really Hard Burn More Calories? Scientific American, July 18, 2012, 13


[i] I’m not referring to chronic fatigue syndrome but to the common fatigue of employees in the modern workplace.