No matter how serious a runner you may be, you don’t give 100% on your runs. Your unconscious brain is keeping your body from hurting itself, and preventing you from reaching your physical limit. Science has good evidence that this is how fatigue occurs in endurance sports.
Fatigue is a Mental Calculation
Exercise science used to advocate peripheral fatigue theory. This states that you decrease your physical exertion when your muscles get tired. But it has problems. The biggest is that as runners approach the finish line they are often able to produce a burst of additional speed to cross it. This is observed in races of 800 meters or longer. It doesn’t jibe with peripheral fatigue because if their muscles were exhausted then proximity to the finish line wouldn’t affect their performance.
In the 1990s an exercise scientist named Tim Noakes overthrew the prevailing wisdom. He posited the central governor theory of fatigue. The idea is that your brain unconsciously regulates exercise performance. It attempts to prevent exertion-caused damage to your body. It makes calculations about how fast and far you can safely run.
The term “central governor” has fallen from favor since there is not one single physical area in your brain that is responsible for this effect. The preferred name is now anticipatory regulation of fatigue though it is sometimes referred to as teleoanticipation or psychobiological model of fatigue. The idea remains the same.
As you start to approach this mentally-imposed performance limit your brain makes you feel awful. Each moment seems an unbearable eternity. Excuses for stopping come readily to mind. You will slow down well before the physical need arrives. This is often seen to be true because after running stops it can be resumed with even greater intensity almost immediately. The “need” to stop was a mirage. While you are experiencing this agony your brain will decrease your muscle activation against your will. So willpower can’t override anticipatory regulation.
Your brain is an amazing effort calculator. There are many inputs to the calculations, including the distance yet to be run, heart rate, oxygen consumption, lactate threshold, core body temperature, muscle fatigue, and so on. Thus it’s not accurate to say that fatigue is only mental, clearly the body is an input. The brain seems to combine all of these factors into a single value that becomes the best predictor of athletic performance: the Rating of Perceived Exertion (RPE). In short, the more effort you feel you are exerting, the shorter the time your brain will allow you to maintain that pace.
Don’t just take it from me. Some of the best evidence for the brain’s role in endurance involves studies of muscle contractions. Exercise scientists have compared quadriceps contractions controlled by the brain versus external magnetic stimulation. They measure the force of muscle tightening in an individual by both methods before and after exercise on a stationary bike. This allows them to compare the physical and mental contributions to fatigue. In a rested state the external stimulation produced contractions 17% stronger than the voluntary ones. But when fatigued the magnetically-caused contractions were 29% stronger than the normal contractions. The brain is clearly unable to fully use the muscles as fatigue occurs.
The worst part is that your brain’s anticipatory regulation system will slow you down before the physiological fatigue starts. This has been shown in studies with subjects on stationary bicycles in hot rooms. The riders would slow their pace down from the very beginning, before their muscles were fatigued and before their core body temperature approached the safety limit of 104 degrees Fahrenheit (40 Celsius). Interestingly, hot rooms with thermostats that were tampered with to give cooler readings do not see this effect to the same extent.
Your brain’s anticipatory regulation can be manipulated in other ways too. It’s been shown that merely rinsing your mouth with sugar water without swallowing it gives your brain the sensation that it has more fuel. Your brain in turn allows the body more effort. Likewise feelings of anger, the act of physically smiling (as opposed to the facial contortions of suffering), swearing, and false information about the duration of exercise can result in the brain allowing the body to push itself harder. Also it appears that certain drugs, such as Wellbutrin or acetaminophen (AKA Tyelonol) can effect anticipatory regulation.
Even performing mentally tiring tasks before a run causes worse performance due to mental fatigue. Subliminal messaging on-screen while cyclists performed “time to failure” trials on stationary bikes has shown that riders shown happy faces or “action words” can exercise for longer than those shown sad faces or “inaction words”. Brazilian researches have shown the same thing with weak electric currents being applied to certain brain regions, creating a 4% improvement in time trials.
What Can You Do About It?
All of this goes to show that endurance has a huge mental component. Perceptions, feelings, and beliefs matter for athletic performance. The question is, how should this knowledge affect the way in which you train? Fortunately, this has been written about more deeply by more accomplished athletes than myself. Matt Fitzgerald in his books, How Bad Do You Want It and RUN: The Mind-Body Method of Running By Feel and [Alex Hutchinson](www.twitter.com/sweat science) in his book Which Comes First, Cardio or Weights and Sweat Science blog on Runners World are great resources. They have both done an excellent job of digesting the technical scientific research of others and explaining it in a way that a layperson can understand. What follows are some of their thoughts. In fact, this entire post I owe to their work.
- Train yourself to better withstand suffering. You should be pushing yourself hard enough on some training runs to experience serious suffering. In fact, experiencing as much misery as you expect to feel during your race is the goal. Exposure to this misery will increase your tolerance for it. This gradually gives your anticipatory regulation system a new baseline for perceived effort. Not only that but it allows you opportunities to develop strategies for coping with discomfort.
- Make your performance personally significant. The more important an event is to you the more agony you will be willing to endure. Carefully choose some key races and workouts and elevate their significance. People can almost always run faster in races than they can in training because they are seen as the culmination of all their hard work.
- Set concrete performance goals. Having clear goals can also increase your capacity to exert yourself. As Fitzgerald points out, “There is no such thing as exercising as hard as you can.” Goals can create an anchoring effect for your brain to take into account with its calculations.
- Get real time performance feedback. On days where you are running faster than expected you can see your good time and use it to spur yourself onward to a PR. Matt Fitzgerald gives a great example of a demonstration he gave at a CrossFit presentation. He asked an attendee to hold a dumbbell at shoulder height with arm extended for as long as possible while Matt silently timed him. Then Matt had him do the same thing with his non-dominant arm. This time he told him the duration of the first attempt and he updated him on his elapsed time. With the real time feedback he held the dumbbell up much longer.
- Assess your mental toughness after runs. Did you ever go slower than necessary to reduce suffering? Write this down in journal or spreadsheet and monitor it over time. The power of writing things down cannot be overstated.
- Perform in front of an audience and compete with other runners when training. Studies have shown that both an audience and the appropriate level of competition affect athletic performance. Since the presence of spectators or other athletes doesn’t cause physiological changes, this is obviously a mental hack.
- Learn to find enjoyment in tough runs that result in improved performance. Steadily getting better at something through hard work can be enjoyable despite the self-torture. It is important to realize that suffering and fun can happen together. People are willing to exert themselves more at things they enjoy doing. Enjoyment makes misery itself more tolerable as has been shown in studies involving exercising mice and chocolate.
- Perform mental exercises before going on a training run. This can help train you to handle mental fatigue during endurance exercise without having to add the wear and tear to your body in order to induce that mental fatigue. This often involves 90 minutes of tedious mental attention on computers.
- Brace yourself for pain during runs. Sometimes athletes look beyond their next race toward other goals and expect to breeze through what is thought to be a routine outing. When they encounter greater than expected suffering this can cause them to have reduced tolerance for it.
To improve at running you need to train your body and mind. Even though fatigue is largely controlled by the brain you cannot override your anticipatory regulation by willpower or a “mind over matter” approach. That’s because anticipatory regulation is an unconscious process. Instead, you can gradually teach your brain what your body is safely capable of doing through deliberately training to suffer.
If you have already tried out some of these ideas I would love to have you comment on how they worked for you. If you are interested in implementing some of these techniques I would love ve to hear how that works out. Maybe you think all this stuff is irrelevant hogwash. That’s fine, I want to know that too.
Happy miserable running!
For further reading you might want to start with Alex Hutchinson’s article What Is Fatigue? in the New Yorker.
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