Pain and Fatigue

Pain and Fatigue

Take away your opinion, and then there is taken away the complaint, “I have been harmed.” Take away the complaint, “I have been harmed,” and the harm is taken away.

Marcus Aurelius, 121 AD – 180 AD

The common – and outdated – view of pain and fatigue is through what is called a “Cartesian” model. This centuries-old concept views the mind and body as separate entities and sees pain as a direct, linear process. Somewhat like an electrical switch sending a signal down a wire to illuminate a light bulb. Likewise, this view of fatigue sees it as another direct process, like a gas gauge telling you how much fuel you’ve got left in the tank.

The problem here is that this way of looking at pain and fatigue is misleading and inaccurate. It fails to account for the complexity and adaptability of our minds and bodies, and the fact that it’s nearly impossible to define where one begins and the other ends.

Biopsychosocial Pain and the Central Governor

The modern medical establishment increasingly views pain through what is called the biopsychosocial pain model, and fatigue through the central governor model. These are distinct concepts, but they share common threads and elements which each influence the other.

Both of these theories view pain and fatigue as complex, predictive emotions involving a constant interaction between the mind and body. They’re not just about what’s happening in the present moment, but what your brain predicts may happen in the future.

The older, more simple view of fatigue framed it as if your body were a car running out of gas. You get tired because you’re low on fuel and/or because your engine (your heart and muscles) can’t burn fuel fast enough to keep up with demands. 

The solution here seems obvious: Keep putting more fuel in the tank as you exercise by constantly eating or drinking sugar and train your aerobic system for increased VO2 max so that you can produce power at a greater rate. 

Nutrition and cardiac power certainly play some role in output and fatigue, but these factors are from the complete picture. The holes in this logic appear when we consider everything else we know about performance and fatigue. For example:

  • Only between 35 and 50% of active muscle mass is recruited during prolonged exercise, and this number only increases to around 65% with maximal effort training. 
  • The top finishers in endurance events rarely have the best VO2 max
  • You will automatically reduce your power output in an event if you’re not sure of when it will end, even if you’re trying to go as fast as possible.
  • A runner will start out a race at a slower pace on a hot day than on a slow day, despite not yet having accumulated any form of fatigue or excess body heat.

Think back to the concept of complex systems that we discuss in our book. Compared to a machine like a car, human bodies are extremely complex. To understand complexity, you need a different set of mental models than you’re taught in traditional education where most things are explained through cause and effect relationships (e.g. event A leads to event B).

One of the principles of complexity is the concept of emergence, or that an outcome isn’t caused solely by any one thing, but arises from everything within the system interacting at once. Pain and fatigue fall in this category.

A 2012 paper listing central-acting factors that influence performance and fatigue includes things like emotional state, mental fatigue, sleep deprivation, recovery from prior exercise, superstitious beliefs, monetary reward, knowledge of endpoint, competition, stimulants, accurate or deceptive feedback, mental skills, body cooling, carbohydrate mouth rinsing, prior experience and visual feedback. 

It also includes sensory feedback such as rate of heat accumulation, oxygenation levels, thirst and fluid loss, and muscle soreness or damage. 

Essentially, your brain is using all of these factors (plus untold others) to calculate how hard and how long you can go. It then tries to set a realistic amount of fatigue to keep you below the calculated threshold of physical damage. In all but the most extreme survival scenarios, fatigue will shut you down well before you can actually break your body because your brain is actively working to keep you below your limits. 

Thus, what’s happening in your mind alters your feelings of fatigue, and these feelings have direct physical impacts on things like stress hormones and power output.

As an example, think of the endspurt phenomenon, in which athletes have a surge of power during the last 10% or so of an event that returns them to almost the same level of performance that they had at the beginning of their race.

They’ve been exhausting themselves at maximal effort for the entire event, have been feeling more and more fatigued, yet once they know that they’re almost done, their brains do a calculation that predicts how much more effort they can expend without damage by the end of the event. Suddenly the brakes are taken off. This is how marathon runners finish the last few hundred yards of their races at a sprint.

Predictions based on associations built with prior experience play a major role in this process. Part of how your brain decides how hard an event will be and how fast you can go without damage is based on how it felt when you did it in the past. 

Pain is a signal – not all signals are accurate

Like fatigue, our experience of pain is complex and can vary dramatically based on our perspective and how we focus our attention. 

Pain, first and foremost, is a signal. Like the fire alarm in your kitchen, it’s meant to protect you. But just like that fire alarm, pain doesn’t always mean that something terrible is happening. The alarm sounds the same whether your house is on fire or you’ve just burnt your eggs. 

Pain works the same way. It directs your attention and changes your behavior. It prompts you to respond to danger, or potential danger. 

Sometimes, this is useful. Pain can alert us to injuries, help us avoid them, and provide guardrails on our movement that allow our tissues to heal. But, like an overly sensitive smoke alarm in your kitchen or your neighbor’s annoying car alarm, this signal isn’t always accurate or helpful. For example, even severe injuries like broken bones are typically healed within 3-6 months. But, we can feel pain around the injured area long after it has healed and is no longer in danger. 

Even more curiously, people with amputated limbs can still feel pain in the limbs they no longer have. That pain is very real, and it feels just as if something awful is happening to the missing arm or leg, but obviously, the cause lies somewhere beyond tissue damage. It’s an error in the signal. 

In fact, even in the absence of missing limbs, we can experience pain without any physical stimuli. We can learn to associate certain situations – even thoughts and feelings – with pain. Our mood and motivations can affect how sensitive we are to pain. 

Pain is not tissue damage

It’s understandable that many people believe that pain correlates with trauma. The worse the pain, the worse the trauma. But that’s not the case. Hurt is not the same as harm. 

Many forms of chronic pain such as lower back pain are only minimally, if at all, related to MRI findings of structural damage. People can be pain-free and fully functional and have issues like herniated discs or facet joint arthritis on an MRI. Likewise, people can have clean MRIs and still feel significant levels of pain. 

As one study put it, “structural findings on MRI are not clearly related to onset, severity, duration, or prognosis of low back pain.” 

This means that pain doesn’t necessarily mean tissue damage. 

Consider, for example, a case reported in the British Medical Journal in 1995. A 29-year old construction worker jumped onto a plank and a 7-inch nail punched completely through his boot. He was in excruciating pain and was started on opioids at the hospital. When the doctors removed the boot, they realized that the nail had passed cleanly between his toes. This doesn’t mean that the pain that the man felt wasn’t real. It just illustrates how emotions like panic and fear can compound our expectations of how we think we should feel, and in turn, what we do feel. The pain that he felt was just as real as if he’d truly had a nail punched through his foot. When he gained new information that enabled him to change his opinion of the situation, his pain immediately resolved. 

In another case, reported in 2007, a man – another construction worker – unexpectedly discharged a nail gun. He felt a thump in the side of his face but didn’t notice any significant damage. Just a little bruising under his jaw and a toothache. Six days later, after working, eating, sleeping, and going about his life as usual, he went to the dentist. An x-ray revealed a 4-inch nail embedded in his head. He didn’t experience much pain because he didn’t expect to feel pain based on the information that he had available. 

How we think about pain can change our experience of pain

Pain is, in a sense, an opinion. It’s also a prediction. Just like fatigue, it’s the result of a process in which our brain takes in a bunch of real-time information, compares it with data from past experiences, and decides what it means. The way we think and feel, and contextual factors like stress, pleasure, excitement, and the focus of our attention all shape how we experience pain. 

These opinions can become habituated, or in more technical terms, they can become conditioned responses. We can learn to feel like we’ve got nails in our heads (or lower backs, or knees, etc) even when there are none. Our brains learn to produce pain in certain situations because that’s what they’ve done in the past, and the behavior has been repeatedly reinforced. Over time, this process gets stronger, just like learning any other habit. 

This means that pain can reinforce itself. If this cycle is not broken, we can associate pain with particular movements or areas long after past injuries have healed or dangerous conditions have passed. When this happens, the volume and sensitivity of the alarm signal ramp up. Old injuries start to hurt again. Movement feels needlessly restricted and jerky. Seemingly small things can trigger pain or cause it to spread. 

Building safety, comfort, and freedom

We are always adapting. Our bodies are in a never-ending process of learning and changing. The associations that we build into our day-to-day lives, as well as our training programs, play a critical role in the direction that these adaptations take.

We’re always training more than muscles. The mechanical adaptations from a workout will fade within days or weeks, but the deeper associations that we make with an activity (whether it’s doing a squat, running, or anything else) can stick around and perpetuate themselves for much longer. 

Our sense of pain, or freedom from it, is heavily rooted in our ability to build associations of safety and comfort into our movements and training.

We do not see the world as it is. We perceive only the world as seen by us. Or, put another way, we only see what we’re looking for. The way we view the world, and our bodies, and how safely and freely we can move, reflects back to us in our perceptions of pain.  

What to do with this information

Our experiences of pain and fatigue, like any other signal, can be calibrated for greater accuracy. We can learn to tell the difference between hurt and harm and turn down the volume on the alarm when we know that it’s not truly alerting us to a catastrophe. 

There are many steps toward doing this. 

The first step is to simply understand the premise of this article: that pain is a complex, predictive signal that is highly malleable and only mildly correlated with tissue damage. In other words, hurt is not the same as harm. Sometimes pain is just something that you feel, and it doesn’t mean anything more. You can change what you feel by changing what you think and, in turn, what you experience. 

But, this article is only a starting point, and it can’t cover everything related to this subject. 

Here are some ways to go further:

  • Go deeper with our book. 

Our book is a good place to start for a much deeper understanding of the full system of factors that relate to developing resilient people in high-performance settings. There, you’ll find in-depth discussions of things like stress, pain and fatigue; the psychological aspects of motor learning and skill development; and mental skills to incorporate into training for better performance under stress and fatigue. 

  • Read free resources.

We also have many free resources on our site

In particular, we have a lot of articles in the mindset category that cover helpful concepts such as unlearning fear, stress mindsets, and managing self-talk. All of these can play a helpful role in learning to move and train with a greater sense of confidence and freedom.   

  1. Learn to move better. 

It’s also extremely important to learn how to move well. Quality must come before intensity in a training process. Only from there are you able to develop your ability to extend quality through greater levels of output (heavier weights, higher volume, under greater fatigue, etc). 

For an in-depth look at movement, we strongly recommend the Movement Foundations course from Resilient Performance. If you take your body and your training seriously, then an investment in learning to move well is worth taking seriously too, and these guys are among the best in the business. This course will provide you with a foundation of knowledge that will help you understand movement. This will give you an informed perspective when it comes to assessing the quality and safety of your own movement so that you can be confident in distinguishing the difference between hurt and harm in your own training. 

References: 

Blascovich, J. and Tomaka, J., 1996. The biopsychosocial model of arousal regulation. In Advances in experimental social psychology (Vol. 28, pp. 1-51). Academic Press.

Gibson, A.S.C. and Noakes, T.D., 2004. Evidence for complex system integration and dynamic neural regulation of skeletal muscle recruitment during exercise in humans. British journal of sports medicine, 38(6), pp.797-806.

Noakes, T.D.O., 2012. Fatigue is a brain-derived emotion that regulates exercise behavior to ensure the protection of whole body homeostasis. Frontiers in physiology, 3, p.82.

Fisher JP, Hassan DT, O’Connor N. Minerva. BMJ. 1995 Jan 7;310(70).

Johnson MI. Trauma and Pain: A Fragile Link. J Trauma Treat. 2017;06(02):10–1. 

Ract I, Meadeb JM, Mercy G, Cueff F, Husson JL, Guillin R. A review of the value of MRI signs in low back pain. Diagn Interv Imaging. 2015;96(3):239–49. 

Berg L, Hellum C, Gjertsen Ø, Neckelmann G, Johnsen LG, Storheim K, et al. Do more MRI findings imply worse disability or more intense low back pain? A cross-sectional study of candidates for lumbar disc prosthesis. Skeletal Radiol. 2013;42(11):1593–602. 

Dimsdale JE, Dantzer R. A Biological Substrate for Somatoform Disorders: Importance of Pathophysiology. Psychosomatic medicine. 2007;69(9):850-854. doi:10.1097/PSY.0b013e31815b00e7.

 

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