Killing You Softly: Stress
A culture of stress
Stress is a necessary and unavoidable part of life, and like many things, it’s beneficial in moderation but harmful in excess. However, it’s no secret that we humans don’t do well with moderation. It doesn’t help matters that being overstressed is culturally accepted and often expected, with many individuals working furiously to cram 25 hours of activities into a 24-hour day. Some of these same individuals even wear their stress like a badge of honor, indicating to the mere mortals how elite they are and effectively shaming anyone who doesn’t follow suit. We’ve all heard or read (or said) phrases like “I don’t need sleep; I’ll get all the sleep I need when I’m dead.”
Being busy doesn’t necessarily translate to elevated stress per se, but a lack of sleep certainly does. Before we go off on a tangent down that rabbit hole though, let’s first orient ourselves to what stress actually is. To quote the scientific literature, “Stress is an essential adaptation necessary for homeostasis, performance and survival. The stress response occurs whenever an individual is faced with an endogenous (internal) or exogenous (external) challenge perceived as unpleasant, adverse or threatening. It can be induced by physical, physiological or psychological stimuli.” (Clark & Mach, 2016) Some researchers use the terms “physical” and “physiological” interchangeably when referring to types of stressors.
As athletes, we know that stress is required during training in order to become stronger, faster, and better at our craft. The right amount of stress will lead to positive adaptations and improvements in performance, while too much or too little will lead to negative adaptations and regressions in performance. Physical demands on the more extreme end of the spectrum don’t always result in undesirable outcomes as long as proper rest and recovery are observed, but all too often we athletes fall short of giving our bodies what they need. (Clark & Mach, 2016) This paradox likely emanates from our inability to skillfully manage other stressors in our lives – stressors that stimulate the same stress management machinery as those of physical origin. The demands placed upon our body’s stress management machinery can become overwhelmed, leaving us unable to cope with continued changes in our internal and external environments (read: resilience is lost). Sustained training under such conditions will inevitably lead to a breakdown in performance at best, and injury or illness at worst.
If we desire to be better athletes it’s critical that we understand stress - what it is, where it appears in our lives, how our bodies respond to it, and how to mitigate it. Getting the most out of our training requires that we have both a basic understanding of stress and an awareness around what our bodies are telling us. Said another way, our individualized training programs should be rooted in science and guided by intuition. The intent of this article is to help with (a fraction of) the general science piece; developing a strong intuitive sense is up to you.
Non-training types of stressors
To reiterate, stress isn’t inherently bad; it’s quite important for keeping our minds and bodies strong and resilient. However, stressors come in many different flavors and if we’re not careful we may wind up with too many of them at once.
We’ve already mentioned physical training, which is an acute, physical stressor. Finding yourself face-to-face with a mountain lion is another example of an acute, physical stressor and a great example for explaining how our stress response system works. As we’ll see in a few more paragraphs, this type of stressor mobilizes resources in our bodies in a way that leads to optimal substrate (e.g. glucose) utilization for maximal physical response. I’m sure my fellow Coloradan, Travis Kauffman, was grateful for this bodily response when he was attacked by a young mountain lion while trail running earlier this year (he subsequently killed the animal via suffocation, article here.
Fasting is another type of physical (or physiological) stressor that leads to stimulation of one of the major players in our body’s stress response system, the hypothalamic-pituitary-adrenal (HPA) axis. Activation of the HPA axis leads to enhanced release of the stress hormone, cortisol. This response makes sense in the context of fasting when you consider that cortisol aids the body by making certain energy sources like glucose and fatty acids available for use. Chemical stressors, such as alcohol, also activate the HPA axis, and over time this can lead to HPA dysregulation and elevated baseline cortisol levels. (Badrick, 2008)
Other types of stressors that our bodies must handle are those of psychological origin. Examples might include getting into a fight with a significant other, getting laid off, taking an exam, or giving a public speech. Although these are less outwardly threatening, they still have the capacity to activate our stress response machinery in the same way that encountering a hungry mountain lion would. Put another way, psychological stressors can be so emotionally charged and physiologically arousing that they actually make us feel like we’re facing imminent death. The magnitude of our physiological response to situations like those mentioned above is directly related to our perception. If we don’t believe getting laid off is unpleasant, adverse, or threatening, we won’t be stressed; if you hate your job, losing it might actually be cause for celebration!
When our bodies respond with high levels of physiological arousal, we’re primed for action, and when no physical activity ensues, we’re left with excess energy substrate and no way to put it to use. This might feel a little like consuming a bunch of Octane then sitting around on the couch, which isn’t necessarily a bad thing on rare occasions – especially regarding intellectual stressors since energy for focus and enhanced short-term memory is beneficial – but is problematic when too frequent. This also underlies my theory as to why I feel better when I work out after an emotionally stressful experience.
Note: For the sake of focus and brevity, we won’t be covering traumatic stress in this article, as exposure to a traumatic stressor can lead to differential long-term changes in the stress response system compared to what is observed in cases of non-traumatic stressors.(Bremner, 2006)
The healthy stress response
For many types of stress, simply removing the source of it or removing ourselves from its presence is enough to mitigate its impact and return to a healthy baseline level of nervous system and hormonal activation. These behaviors are commonly referred to as fight (elimination of the stressor) or flight (removing ourselves from its presence) and are supported by our body’s integrated stress response system. There are two major components to this system that enable fight or flight to occur: the autonomic nervous system and the aforementioned HPA axis.
When presented with an acute stressor like the sudden appearance of a mountain lion, the part of the autonomic nervous system responsible for mobilizing bodily resources to fight or flee is the sympathetic nervous system (SNS). When activated, the SNS stimulates the release of norepinephrine (noradrenaline) and epinephrine (adrenaline), and these neurochemicals have widespread effects in the body. Specifically, epinephrine released from the adrenal glands acts on various organs in the body to mobilize glucose and fatty acids and increase their levels in the blood to provide sufficient energy for cells with high metabolic demand like those of our working muscles. Epinephrine also increases heart rate and respiratory rate, enhances short-term memory, increases airway diameter, and enhances muscle contraction. The sum total of these effects is a body prepared for maximum physical response.
Besides stimulating the release of epinephrine by the adrenal glands and the resulting effects listed above, SNS activation also leads to vasoconstriction, or the shunting of blood away from organs such as the skin, digestive tract, and kidneys in order to divert a sufficient amount of blood to working skeletal and cardiac muscles, lungs, and brain. Again, these effects are beneficial and necessary for an individual about to take action. We clearly don’t want a significant amount of our blood going to our digestive system to absorb nutrients from that Chipotle burrito with extra meat and guac (sorry, Brooke, I know it’s not on the meal plan) when we simultaneously need that blood to provide glucose and oxygen to and clear metabolic waste from our muscles. This system is optimized for use in situations of high intensity but short duration.
The ideal state in which to remain, outside of acute bouts of training, competing, operating, performing, etc., is one that is predominantly driven by the opposing part of the autonomic nervous system, called the parasympathetic nervous system (PNS). This system is also referred to as the “rest and digest” system. As this phrase suggests, when the PNS predominates our bodies are primed for activities related to eating, digestion, and sleep. All of that said, activation of the PNS and SNS isn’t an “either/or” situation; rather, it’s a “both/and.” What this means is that at any given time the SNS and PNS are both functioning, but the degree of dominance of one over the other shifts depending upon our needs from one minute to the next.
The HPA axis is the other component to the body’s integrated stress response. As the name suggests, it involves the hypothalamus, pituitary gland, and adrenal glands and it’s responsible for regulating the release of the steroid hormone, cortisol, among other hormones, through a negative feedback loop. Cortisol is closely related to cortisone, the substance doctors inject into our joints to suppress inflammation and decrease pain. Cortisol suppresses inflammation by interfering with our body’s immune response. In addition to suppressing inflammation, cortisol has parallel functions with epinephrine, including increasing blood glucose levels, mobilizing free fatty acids and amino acids, and enhancing memory for highly emotional events. (McGaugh, 2013) Interestingly, cortisol impairs the retrieval of long-term memories (i.e. you have difficulty remember something you already learned when cortisol is high), likely through its prolonged interaction with receptors in a major memory center in the brain called the hippocampus. (de Quervain, 1998, 2000; McAuley, 2009) Cortisol’s normal pattern of release outside of enhanced SNS activation is one that follows our natural sleep/wake cycle, peaking upon morning waking and reaching a 24-hour low somewhere during mid-sleep.
The pathological stress response and chronic stressors
It’s clear that stressors are a natural part of life and our bodies have an effective and elegant system for handling them. However, this system wasn’t designed to be stuck in the “on” position. The consequences of chronic stress are severe and too complex to cover in detail here, so we’ll just take a look at a few of the athlete-relevant examples.
Prolonged stress can lead to chronic hypercortisolemia, or abnormally high levels of cortisol in the blood, which has widespread negative effects in the body. Its impact on the brain includes impaired memory and associated negative functional and structural changes in the memory center of the brain called the hippocampus. (de Quervain, 2000). With regard to athletic performance, persistently high levels of cortisol can lead to proteolysis and the breakdown of muscle tissue, which is counterproductive when trying to increase strength and stamina by building muscle. Elevated cortisol can also interfere with bone and collagen formation, potentially leading to osteoporosis and connective tissue dysfunction in the more extreme cases. These effects can unsurprisingly lead to poor healing following fractures or soft-tissue injuries to tendons, cartilage, ligaments, and skin, which already take a very long time to heal.
Prolonged stress also impairs our immune system to a shocking degree. While acute stress enhances inflammation and increases blood levels of pro-inflammatory cytokines to assist with the elimination of pathogens and initiate healing, chronic stress leads to chronic inflammation and immune system suppression and dysregulation. This increases one’s risk for a variety of health problems, including enhanced susceptibility to illness and infection, atherosclerosis, autoimmune diseases, latent virus activation (e.g. shingles), and exacerbated symptoms of both physical and psychological illnesses. (Morey, 2016)
This may sound too hippie to be true, but according to Langgartner and colleagues, the “increases in immune (re-)activity and inflammation, potentially promoted by a reduced exposure to immunoregulatory microorganisms (also known as "Old Friends", or bacteria frequently found in soils) in today's modern society, may be causal factors in mediating the vulnerability to development and persistence of stress-related pathologies.” (Langgartner, 2019) In other words, we’re spending less time outside and in contact with the dirt that contains helpful microorganisms responsible for promoting a healthy immune system and keeping inflammation at bay. According to this theory, it is this loss of our “Old Friends” that promotes a dysregulated immune system and inflammation, ultimately giving rise to chronic stress-induced disorders such as inflammatory bowel disease, posttraumatic stress disorder, anxiety, and depression. (Langgartner, 2019) Maybe this is part of the reason why it feels so good to get dirty on a mountain bike ride. It’s certainly food for thought.
Let’s briefly return to sleep. In my opinion, one of the most disturbing consequences of prolonged stress is insomnia. I can’t emphasize enough how important sleep is to our overall health and well-being, and for athletes it’s also critical for achieving optimal performance and recovery. We know that stress activates the SNS, and SNS activation increases the body’s metabolic rate, subsequently elevating core temperature. This increase in temperature interferes with sleep onset, which requires a drop in core temperature by a few degrees. SNS activation also leads to the release of the neurochemicals cortisol, epinephrine, and norepinephrine which collectively influence brain activity in regions responsible for alertness and emotional processing, further contributing to problems with sleep onset. A third factor affecting sleep onset is the SNS-induced increase in cardiac activity. Finally, assuming you’re eventually able to fall asleep, SNS activity hinders the depth of deep sleep and leads to sleep fragmentation. Trust me when I say that none of these effects are helpful for a body in need of rest and recovery. For more info on sleep and its central role in health, read Why We Sleep by Dr. Matthew Walker – I promise that it’ll change your life.
What to do to mitigate stress
Although it may seem like we’re all doomed to having a relationship with stress that necessarily leads to physiological and psychological dysfunction, this doesn’t have to be the case. There are a variety of things we can do to diminish the number of stressors in our lives and at the very least, mitigate their impact. Regarding psychological stress, perception is reality so if we can work on changing our perspective we can influence our level of stress. Part of a helpful perspective shift is recognizing things we can control and therefore change vs. things that are beyond our control. I know it’s a clichéd statement but making peace with and letting go of the things we cannot change is extremely helpful. Saying “no” more frequently is also quite liberating and can lead to significant peace.
Other helpful tools include regular sleep, exercise, meditation, and yoga. We know that regular moderate exercise decreases baseline cortisol levels, and we also know that the negative effects of elevated plasma cortisol levels on cognition can be mitigated by blocking plasma cortisol. Thus, exercise may lead to better plasma cortisol regulation, which may in turn lead to improved hippocampal activity and memory. (McAuley, 2009; study conducted in the elderly) As for meditation, the number of research studies in support of various types of meditation for stress reduction and overall well-being continues to increase. A recent review by Brandmeyer and colleagues states, “There is a growing body of evidence demonstrating positive benefits from meditation in some clinical populations especially for stress reduction, anxiety, depression, and pain improvement…” (Brandmeyer, 2019) The effects of yoga appear to be very similar to meditation regarding stress reduction. (Mohammad, 2019) Specific benefits have been found to include reduced levels of cortisol, blood pressure, and resting heart rate, increased heart rate variability, and better control of substrates such as glucose, cholesterol, and low density lipoproteins. (Pascoe, 2017)
Perhaps unsurprisingly, spending time in nature can lead to significant stress reduction. This isn’t just due to the fact that nature is quiet, peaceful, and beautiful; it’s also due to the fact that in nature we come into contact with our “Old Friends,” or the microorganisms with which mammals co-evolved, as mentioned above. Throughout human evolution, the interactions between these ancestral microbiota and the innate immune system promoted healthy immunoregulation. However, due to practices such as sanitation, drinking water treatment, excessive use of antibiotics, changes in diet, and increased time indoors, individuals in urban environments infrequently come into contact with these helpful microorganisms. (Langgartner, 2019) It’s not a fluke that inflammatory diseases and stress-related disorders are more prevalent in urban environments as compared to rural ones. Bottom line: get outside and play in the dirt in as many biodiverse places as you can, or if you need something more intense, go for a mountain bike ride and grin so big that the dirt from your front tire flings straight into your mouth.
Since I started this piece with a reference to moderation as it relates to stress I’ll end it with one, too. Former Army Ranger and current yogi and author, Rolf Gates, says “Despite the staggering amount of evidence that excess destroys our dreams, there appears to be a human blind spot when it comes to the possibility that our most passionate existence might actually be accessed through balance and moderation.” Maybe ponder that on your next nature walk. Now get outside and Die Living.
Badrick E, Bobak M, Britton A, Kirschbaum C, Marmot M, and Kumari M. The Relationship between Alcohol Consumption and Cortisol Secretion in an Aging Cohort. J Clin Endocrinol Metab. 2008 Mar; 93(3): 750–757.
Brandmeyer T, Delorme A, Wahbeh H. The neuroscience of meditation: classification, phenomenology, correlates, and mechanisms. Prog Brain Res. 2019;244:1-29.
Bremner JD. Traumatic stress: effects on the brain. Dialogues Clin Neurosci. 2006 Dec; 8(4): 445–461.
Clark A & Mach N. Exercise-induced stress behavior, gut-microbiota-brain axis and diet: a systematic review for athletes. J Int Soc Sports Nutr. 2016 Nov 24;13:4312:43.
de Quervain DJ, Roozendaal B, McGaugh JL. Stress and glucocorticoids impair retrieval of long-term spatial memory. 1998. Nature. 394 (6695): 787–90.
de Quervain DJ, Roozendaal B, Nitsch RM, McGaugh JL, Hock C. Acute cortisone administration impairs retrieval of long-term declarative memory in humans. Nat Neurosci. 2000 Apr;3(4):313-4.
Langgartner D, Lowry CA, Reber SO. Old Friends, immunoregulation, and stress resilience. Pflugers Arch. 2019 Feb;471(2):237-269.
McAuley MT, Kenny RA, Kirkwood TBL, Wilkinson DJ, Jones JJL, Miller VM. A mathematical model of aging-related and cortisol induced hippocampal dysfunction. BMC Neuroscience. 2009; 10:26.
McGaugh JL. Making lasting memories: Remembering the significant. Proc Natl Acad Sci U S A. 2013 Jun 18; 110(Suppl 2): 10402–10407.
Mohammad A, Thakur P, Kumar R, Kaur S, Saini RV, Saini AK. Biological markers for the effects of yoga as a complementary and alternative medicine. J Complement Integr Med. 2019 Feb 7;16(1).
Morey JN, Boggero IA, Scott AB, Segerstrom SC. Current Directions in Stress and Human Immune Function. Curr Opin Psychol. 2015 Oct 1; 5: 13–17.
Pascoe MC, Thompson DR, Ski CF. Yoga, mindfulness-based stress reduction and stress-related physiological measures: A meta-analysis. Psychoneuroendocrinology. 2017 Dec;86:152-168.