Is Fatigue all in your Head? Ed McNeely, MSc., Strength & Conditioning Lead
There was a popular children’s bedtime story called the Little Engine that Could. In that story, a train engine struggled to get up a steep hill but by repeating the phrase “I think I can” over and over, he made it up. Little did we know at the time, that train engine had stumbled upon the secret to overcoming fatigue in many sport situations.
Research into fatigue has tended to take a systems approach, focusing on one single cause at a time. As a result we have gone through periods where lactate was the cause of fatigue, glycogen depletion was the cause, heat was the cause etc. etc. etc. This was great fodder for discussion boards and magazine articles but it never really explained why an athlete fatigues and why athletes fatigue at different rates.
Several years ago the notion that the brain was the sole cause of fatigue was put forward as a theory called the Central Governor theory. This theory met with a lot of resistance from the scientific community and some heated debates played out in several sports science and sports medicine research journals. While there are flaws and areas of contention in many scientific theories the notion that the brain is responsible for fatigue makes a lot of sense and explains many of the practical experiences of coaches and athletes.
In simple terms, when you start to exercise your brain sends out signals to your muscles to make them move. At the same time signals come back to your brain from your body to help your brain adjust the exercise. Your brain is monitoring things like lactate levels, carbohydrate levels, heart rate, breathing rate, temperature, changes in hormones, muscle soreness and pain. When all these elements are within certain parameters your brain is happy to let you go along doing your exercise. As the feedback from your body starts to get more intense your brain starts to tell you that the exercise is getting hard and isn’t something that you normally do. This is when you start to ask yourself if you want to continue. At this point you have the option of consciously telling your brain that everything is OK keep going or you can tell your brain that things may not be OK maybe we should stop. At some level of difficulty the signals coming back from your body that tell your brain not to keep going will overwhelm the signals that you consciously send to keep going and you will stop.
The process of training and getting fitter is designed to increase the speed or power at which the “stop” signals get too strong to keep going. But there is also a perception component to fatigue. As you expose yourself to harder exercise more frequently your brain gets used to the intensity of the signals coming back and realizes that the pain you are experiencing is not dangerous and you can push through. The next time that you are struggling with a workout and your brain starts to ask if you are sure that you can go on remember the Little Engine that Could. If you think you can you probably will.