Science of Running and Mental Fatigue

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When we think of ultrarunners, we think of people with iron wills and the ability to push themselves beyond their limits. They seem to override physical fatigue with mental toughness. Finding causes of fatigue has been at the center of exercise physiology research for more than 100 years.

For much of the last 50 years, research has focused on fatigue as it relates to the peripheral tissues: skeletal muscle and cardiac muscle. Stemming from the work of Nobel Prize-winning physiologist A.V. Hill in the 1920s, the concept of peripheral fatigue has dominated many of our ideas and subsequent research. However, more recently, others have proposed alternative mechanisms of fatigue due to known inconsistencies in the peripheral theory. For instance, one study looked at the physiological responses to a four-hour treadmill run. After four hours, subjects’ ability to maximally contract their quadriceps was decreased by 25%. However, when subjects’ quadriceps were electrically stimulated, they still had the capacity to contract maximally, with no 25% decrease. If fatigue were in the muscle alone, the muscle would likely not be able to contract maximally after four hours of running.

The most prominent alternative hypothesis for fatigue is the “central governor theory,” which has been championed most vigorously since the early 2000s by the outspoken South African Professor Tim Noakes. Noakes, building on the work of others, basically argues that our brains anticipate how hard to work based on the effort, environment and our mentality. That anticipated effort is subsequently communicated to the muscle, essentially telling us to speed up or slow down. Support for the central governor theory comes from a number of studies that show that purposefully deceiving subjects can lead to improved performance.

Three such examples are the use of a clock that runs slowly, which tricks subjects into maintaining a maximal effort longer; providing a pacer that moves 2% faster than the subject thinks, which tricks the subject into a faster performance; and telling the subject that the temperature is significantly cooler than it really is, which tricks the subject into exercising longer, with the physiological consequence of a higher core temperature compared to when subjects are told the correct temperature. These studies suggest that we anticipate how hard we can exercise depending on our perception of the situation, making adjustments based on our anticipated effort.

However, the deception can be too great. When subjects try and race a pacer that was going 5% rather than 2% faster than their best effort, they still managed to beat their best time, but lost some self-efficacy, or drive, to complete the time trial. So pacers should keep the level of deception realistic. Try not to tell your athlete there is only 10 miles to go when there are 15 miles left, otherwise, with 5 miles to go they may just give up.

Our anticipation for a given effort results from how we feel about the external cues that we know alter our performance. Naturally, scientists have conducted experiments that manipulate our so-called internal environment, or cognitive function, to see how that alters performance. In these studies, scientists assign the subjects a cognitively demanding task to fatigue working memory or vigilance, which is the ability to correctly distinguish between objects, letters, pictures, etc. The result is mental fatigue. After scientists induce mental fatigue, they have the subjects perform an endurance exercise effort to failure, or a time trial effort. Consistently, subjects who are mentally fatigued perform poorly compared to control conditions. Conversely, scientists have also performed studies to determine psychological strategies to increase endurance performance. Studies show that psychological skills training in general (self-efficacy and emotional control) and motivational self-talk specifically can improve endurance performance. We all know that successful runner who thought it was a lot cooler than it was on a hot day or just never “felt” the altitude despite coming from sea level.

One caveat to these studies is that few have been done on ultra athletes or over ultra length exercise duration. However, one recent study attempted to address how cognitive functioning predicts ultra performance. In this study, scientists divided the ultrarunners into two groups, fast and slow, and conducted a number of cognitive tests on each group. The faster runners were better able to avoid incorrect responses by ignoring irrelevant information, and had faster working memory response times when emotional stimuli were present. Essentially, faster runners have better cognitive functioning. However, whether faster running leads to better cognitive functioning, or if better cognitive functioning leads to faster running cannot be determined by this study. Still, taken together with all of the other data, there seems to be a link between endurance performance and psychological skill.

So how can one improve these traits? Well, a sports psychology specialist can teach the psychological skills associated with improved mental cognition and willpower. Additionally, there are published studies which use programs to improve working memory that also have a transfer of benefits to other psychological skills, unlike the evidence associated with so-called brain training companies. You can actively train your mind to harness your willpower and determination to push past your self-imposed physical limits to get the best not only out of your body, but out of your mind as well.

References: Noakes TD (2012) Fatigue is a brain-derived emotion that regulates the exercise behavior to ensure the protection of whole body homeostasis. Front. Physio. 3:82.

Cona G, Cavazzana A, Paoli A, Marcolin G, Grainer A, et al. (2015) It’s a Matter of Mind! Cognitive Functioning Predicts the Athletic Performance in Ultra-Marathon Runners. PLoS ONE 10(7): e0132943.

Marcora SM, Staiano W, Manning V (2009). Mental fatigue impairs physical performance in humans. Journal of Applied Physiology. Vol. 106 no. 3, 857-864

Blanchfield AW, Hardy J, De Morree HM, Staiano W, Marcora SM. (2014). Talking yourself out of exhaustion: the effects of self-talk on endurance performance. Med Sci Sports Exerc. 2014;46(5):998-1007.

Mind Builder: The Working Memory and Attention Training Game. www.chriskanan.com/wp-content/uploads/Game.html

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About Author

Matt Laye has a PhD in Medical Physiology and is an Assistant Professor of Health and Human Performance at The College of Idaho and lives in Boise, ID. He enjoys competing on trails and on the roads in distances from the mile to 100 miles. He has averaged under 8 min/mile for 100 miles and under 5:30/mile over a marathon.

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