Stress, gut, and performance: body-brain connectivity in endurance sports

March 17, 2017

Stress, is commonly defined as threats to homeostasis (i.e. the self-regulating process towards physiological balance of biological system), and because of its definition is has been popularly promoted sole as a negative state. Stress in sports psychology can be defined as the imbalance between demand and perceived response capacity, that can be translated to for example how much one perceive to be able to accomplish a certain task. Such definition is more interesting because makes us see stress through a different perspective that involves both positive and negative aspects of it. Yes, stress can also be a good thing.

I know it might sound a bit strange to some of you, but it is not so complicated. You see, western thinking was mostly developed along a dualistic idea in which one thing is either good or bad, but not both. Only recently, this rationale is starting to be replaced by a more complex way of seeing things. A way in which one factor can have different effects on human neurophysiology and behavior depending on how intense, prolonged, and in which situation it is present. And stress is one of these factors.

Optimal stress is the level of stress that creates motivation and makes a person perceive a task or demand as a challenge. Such perception varies according to the sport modality and personality traits, however extreme levels of stress (either low or high) always create negative outcomes that can either lead to far from optimal attentional levels, low motivation, and depressive states (in cases of extreme low stress); but it can also lead to high levels of anxiety, impaired attention, motor control, immunologic system, and energetic efficiency (in cases of extremely high levels of stress).  

But the effects of the body-brain connection are felt not only on our attention levels. Our body and brain (and consequently our behavior) are closely connected and this communication goes both ways. Thus, the brain sends signals that affect the body, but the body also sends signals that affect the brain and our behavior. Stress becomes then a perfect illustration of this two-way communication because it can affect the body (e.g. when the signal is promoted because of a certain mental projection, memory, situation or environmental pressure) and also the brain and our behavior (e.g. when the signal is promoted due to disturbances in our body, such as due to the activity of pathologic agents or hormonal variations). 

More recently, the efforts to better understand this communication led scientists to discover an important connection between the brain and our gastrointestinal tract (i.e. our guts). The gut-brain connection occurs via the vagus nerve and is currently being categorized by some as a third nervous system, comprised of more than 100 trillion microbes that live in your large and small intestine. More interestingly, the ENS or Enteric Nervous System, seems to have the ability to influence not just our cravings but also our behavior, and emotional regulation.

Listen to your guts but don’t always follow it.  

Because the road goes both ways there is many things that we should be aware regarding not just how our current emotional state affects our guts, but also how our guts affect our emotional state. When it comes to body-brain connection we seem to easily fall on a sort of spiral effect. We currently know that extreme stress causes cortisol deregulation and impacts the stability of the microbiota, leading to a series of outcomes such as:

1) Alterations in gastrointestinal motility (digestive process);

2) Increase in visceral perception (more sensitive to the activity of the internal organs);

3) Changes in gastrointestinal secretion;

4) Increase in intestinal permeability (increase in the number of foreign compounds entering the bloodstream);

5) Negative effects on regenerative capacity of gastrointestinal mucosa and mucosal blood flow;

6) Negative effects on intestinal microbiota or bacterial translocation;

But before you rush to think that these outcomes are completely bad, try to first take into consideration the evolutionary explanation to such adaptations. That is, even though changes in gastrointestinal activity and in it microbiota can lead to subsequent weight gain, sleep disturbances, and even impact on life span, these symptoms are signals that have promoted evolutionary advantages to our survival, once they help in inducing behavior to find high caloric food such as sugar and fat, which are closely related to our evolutionary survival mechanism. Our body cannot distinct chronic (or even acute) stress caused by an important competition or long training sessions, at the end it truly thinks you might be in real danger. Thus, once you start to crave for sugar or fat, try to think twice if that might be occurring due to the lack of it in your organism of if it might be happening because of stressful situations and anxiety states.

But as I said, the road goes both ways. Difficulty to lose weight and obesity, for example, are linked to genetic disposition and also to how “healthy” and diverse your microbiota is. Moreover, certain bacteria that are currently rare in our system such as H. pylori might also impact on appetite by modulating a hunger stimulating hormone called ghrelin

In that sense, the “eat less, exercise more” approach is limited to the sense that it only takes into account variation in the volume of training and food intake, without considering the importance of food quality, diversity, and personalized training focused on the biological uniqueness of each person. Although diet change has influence on the composition of the gut microbiota, some of its specifics aspects are still under discussion. So far, what is known is that Western diet usually low in fiber and high in fat and refined carbohydrates seems to point to early (and bad) differences in the microbiota composition, while whole grain products might actually contribute to a possible bifidogenic effect (i.e. the growth of bifidobacteria or “good bacteria”).

And although its seems difficult to change the gut microbiota cocktail, the impact of a “healthy” diet might be of great importance for breastfeeding mothers, once the human gut microbiota seems to be formed during the first three years of a child’s life and thus directly affect by breast milk, vaginal bacteria from the birth process, and other types of food consumed during these first few years of life. Thus, as this is a crucial period for learning it might also be a crucial period for earlier and later physical and mental health - note that multiple sclerosis as well as Alzheimer’s disease might also be linked to the influence of our gut microbiota on the brain and rest of the body.


TIPS on managing stress to have a healthier microbiota

While the specificities of what type of food can affect the gut microbiota are yet to be discovered, we know that stress management techniques and psychotherapy options can also help regulate gastrointestinal distress. This is of major importance for endurance athletes once the level of stress is usually very high due to the also high and constant volume of training. More recently, I’ve been working with Dr. Minozzo and a few athletes on the development of a training system for runners, swimmers, cyclers and triathletes based on the many concepts that surround the body-brain connection (see the program here). But while we don’t have the program completely structured, you can already try to follow some of these tips to manage your stress:

  • Try to have a good (and dark) night of sleep: according to Konturek and colleagues (2011), “melatonin is an important mediator of brain gut axis has been shown to exhibit important protective effects against stress-induced lesions in the gastrointestinal tract”. Melatonin is a hormone that regulates the circadian cycle and its levels depend on the presence or not of light during resting and wakefulness periods. Therefore, having a constant routine of waking up early and going to bed early will probably allow you to have a more balanced level of melatonin;


  • Resting days: make sure you have enough resting days and that you truly rest during your resting days. For that you have to know how to plan your resting days according to your training load and also the type of lifestyle you have. I’m not saying that you should stay at home all day doing nothing, but you should do activities that can lift your mood, make you laugh, and that don’t require a lot of physical effort. Don’t fall into the myth of training to exhaustion, such and idea can actually lead to chronic fatigue and deplete whatever motivation you have to exercise. Find yourself a good coach that knows how to plan your training load and that takes into consideration your lifestyle, athletic experience, time availability, and biological uniqueness;


  • Meditation and relaxation techniques: when it comes to mental preparation in sports, what usually comes into people’s mind is the idea of training your focused attention to get into “the zone”. Although important, this is only part of the story. Great athletes know not just how to find an optimal level of attention but also how to reduce tension and anxiety in order to properly rest. Remember, when we talk about stress we have to always think of how to manage it, meaning learning how to increase and decrease the effect of it in our body and mind. One of the most ancient methods of stress management is meditation, an idea that is basically grounded on training one’s mind to enhance body-awareness and emotional regulation by controlling one’s focused attention to achieve and sustain neutral or positive emotional states. There are various number of techniques and you must be aware that different techniques induce different results, so make sure you search and find for a method that truly speaks to what you want to achieve.



Felipe Almeida


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