Is Your Brain Getting In Your Way? – More Evidence that Your Brain Causes Running Fatigue

By Rick Morris

Runners aren’t often accused of thinking too much. After all, how much brain power does it take to keep putting one foot in front of the other lots and lots of times? For most of us our most brain straining event of the day is whether to do an eight mile tempo run or head to the track for some interval training. That makes the latest scientific research proving that our brains are really in charge of our running all the more surprising. Does it affect your running fatigue?

In recent years many researchers and exercise scientists have been engaged in ground breaking research concerning the cause of running fatigue. This new area of study came about because of the inability of the current theories of running fatigue to explain some running performances. The most commonly accepted reasons for running fatigue had been related to “catastrophic” occurrences such as, peripheral muscle fatigue, energy depletion and a loss of metabolic homeostasis. The problem was that many performances such as ultra marathon running and increasing to sprint pace at the end of a marathon should not be possible if those catastrophic reasons were the true causes of all running fatigue. That led to a new theory of a central governor fatigue caused by the protective action of your central nervous system.

The newer central governor theory seemed to answer the previously unanswerable questions about running fatigue, but in its early stages this new theory had only a small amount of scientific evidence to back it up. Now there is more evidence  that further supports the idea that your brain is highly involved in running fatigue and performance.

A study conducted at the University of Wisconsin Medical School enlisted the help of eight  competitive male cyclists. Each cyclist completed three 5K cycling time trials on separate days. The first time trial was performed in a fresh state with no pre-exhaustion. For the second test the cyclists rode to exhaustion at 83% of peak power and then after a 4 minute rest performed the 5K time trial. The third protocol involved pre-fatigue ride at 67% of peak power and 4 minute rest followed by the 5K time trial.

The researchers found that the central motor drive (voluntary muscle activation), power output and exercise performance were highest during the  trial performed without pre-fatigue and lowest after the 83% pre fatigue time trial. That finding isn’t at all surprising. It just makes common sense that you will perform better when you start in a fresh, non-fatigued state. Nothing new there – right? The really interesting part of this study is what the researchers found when testing the actual fatigue levels of the subjects quadriceps muscles. They found the amount of peripheral muscle fatigue was identical after all three time trials despite the large differences in power and performance. The researchers said “We conclude that feedback from fatiguing muscle plays an important role in the determination of central motor drive and force output, so that the development of peripheral muscle fatigue is confined to a certain level.”

In simpler terms these researchers are saying and confirming what the earlier research into brain caused muscle fatigue said – your central nervous system can and will control muscle neuron activation to keep peripheral muscle fatigue, metabolic fatigue and energy depletion fatigue within manageable levels.

The obvious question is how do you train your body and central nervous system (CNS) to become more efficient and improve your running performance? There has been very little research on that subject and more needs to be done to determine the best way to train your CNS and how it responds to your running. For now your best bet is to keep doing that high intensity training such as interval training, lactate turn point training and tempo running. This type of training will take your body outside the state of homeostasis that your CNS likes. I believe that high intensity training will force a “reset” to a higher level of what your CNS considers to be acceptable. You will be able to run at faster paces for longer periods of time before your CNS cuts in and tries to slow you down.