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3 Ways to Know Mental Fatigue is Impairing Sports Performance

Learn about the athlete mental fatigue during sports.

swimmer with mental fatigue

You know those crazy kids in high school that decide to take on an insane load of honors and AP classes and do sports at the same time? So do I. In fact, I was one of them. After the 7 hours of listening to lectures, writing essays, and solving math problems, swimming was my escape. I wasn’t the best at it, but it was something I enjoyed and looked forward to most days. Once I entered that pool deck, the pile of books and homework I had was left inside the locker would not affect me for the next 2 hours in the pool. In fact, not much would be remembered from outside that pool deck except perhaps the songs stuck in my head while doing the longer sets and our coach yelling at us to go faster. That’s what I thought back then. It was a nice thought. However, a recent study on mental fatigue seems to have proven me wrong. All that juice my brain used up on multiple tests a day sometimes apparently did affect my body’s performance.

What is Mental Fatigue?

Mental fatigue is defined as an acute increase in subjective ratings of fatigue and/or an acute decline in cognitive performance. It is induced by prolonged periods of demanding cognitive activity. This is not the fatigue that one achieves by not sleeping enough the night before. Nor is it the fatigue related with old age or disease. Mental fatigue is caused by engaging in activity that requires heavy mental focus for long enough to feel that your brain is out of juice.

How Mental Fatigue Affects Athletic Performance

Now that we understand what mental fatigue is, let’s dive into it’s effects on running performance. A recent study collected 10 male participants in their early 20s who were already part of competitive sports like soccer, football and rugby.The aim of the experiment was to study the perception of effort and performance. However, the participants were told something different in order to avoid placebo effects.

After using a computer program to induce mental fatigue, the participants were to perform the running protocol. This was designed to reflect the running demands of various team sports such as football, rugby, hockey and soccer. Data was collected on both the low intensity performance and the high intensity performance.

The results above were in agreement with what was being expected. The group that was mentally fatigued performed significantly lower in the low intensity (LIA) test. This included walking, jogging and running up to 50% of maximum possible effort. As for the high intensity (HIA), the performance of the mentally fatigued group did not differ significantly from the control group. High intensity included fast running and sprinting with 70-100% effort. The reason for the impairment is that mental fatigue heightens the perception of effort.

How to Monitor Mental Fatigue

Mental fatigue is slightly difficult to monitor at first. Different types of fatigue are confused and blended many times by people. However, if you’ve been eating right, sleeping right, and getting all the proper rest from physical activity yet you’re still feeling many of the symptoms of fatigue, it could be coming from your mental activities. Reading those textbook chapters and writing an essay before coming to practice could do the trick.

3 Symptoms of Mental Fatigue

1) Increase in Errors

For this one you’ll need to look back a little. Mental fatigue causes a person to start make more mistakes than usual. So ask yourself, how clumsy have you been lately? Do you find yourself getting clumsier as the day goes by? Or worse, do you find you have been getting more clumsy each day? This is a good indicator to start off with.

2) Frustration Trying to Complete Easy Tasks

Mental fatigue will cause tasks to seem much harder than they are. When in the middle of a task, you find yourself getting frustrated more and more while your brain only shuts down more with each try, you can add that to the list of symptoms

3) Short Attention Span

Last but not least, is your attention span gone? Mental fatigue is known to lower concentration so if you just can’t keep your mind on the task at hand, it is a good indicator to start off by. You can test this by focusing on anything. One easy way is to sit down and breathe. How  long can you focus on breathing down into your stomach before something else snatches away your mind’s attention?

Test Your Mental Fatigue

If you find yourself stuck in a loop of these symptoms, you can also take a questionnaire to diagnose yourself. The Brunel Mood Scale, also called BRUMS, is a test you can easily find online. This test will give you subjective ratings on a couple of areas in your life. For mental fatigue we will be checking your subjective ratings of fatigue and vigor. An increase in subjective ratings of fatigue and/or a reduction in subjective ratings of vigor are well-established markers of fatigue in athletes.

Solutions for Mental Fatigue

There are no quick fixes for mental fatigue but of course there are ways to recover from it.

1) First of all, make sure you’re sleeping enough. Sleep is how we naturally repair. Not getting enough sleep is just promising yourself for these things to happen.

2) Next, to recover properly each time you sleep, your body will need proper nutrients. It’s time to start adding those greens into your diet. Plant based foods have way more antioxidants than dairy products and meat.

3) Also, avoid alcohol and coffee. Adding depressants into your diet definitely does not help your brain or body recover from anything. As for coffee, it can be somewhat of a temporary solution, but in the long run it will increase fatigue while robbing your body of minerals, water and other nutrients. Being an athlete, your body will need optimal hydration and proper nutrient absorption anyways.

4) It wouldn’t be a bad idea to learn how to meditate. Meditation has shown to help reduce and manage stress while improve your concentration ability. Also, concentration one of the important abilities you lose when mentally fatigued. It’s a great preventative measure.


  1. SMITH, M. R., MARCORA, S.M., Coutts, A.J. Mental Fatigue Impairs Intermittent Running Performance. American College of Sports Medicine. August 2015. doi: 10.1249/MSS.0000000000000592.

Written by Parth Rajput, COR Intern