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Stress stimulates appetite, it increases abdominal fat, it increases risks for disease and it can even play a role in our intimate relationships.
The list could keep going, but what exactly is stress and how is it connected to all these consequences? This guide will provide you with a thorough understanding of many aspects of stress.
Scroll down to get started!
You can find more about stress – and how it relates to exercise – within the NASM- CPT program.
But for now, read on!
Stress can be is defined as a nonspecific response to any stimulus that overcomes, or threatens to overcome, the body’s ability to maintain homeostasis (state of equilibrium of the body’s internal biological mechanisms) (1). In other words, when the body is exposed to, or anticipates a stressor, it initiates a response mechanism to help restore a state of equilibrium.
However, it is important to remember that this biological response is essentially the same regardless of the type of stress we impose upon ourselves, and only differs by magnitude of the response needed.
Our stress-response mechanism is designed to respond to acute physiological stresses – ones that place stress upon our body for only short periods of time (e.g., escaping a sabre-tooth tiger) where we respond with physical work.
We often refer to this mechanism as our ‘fight-or-flight’ response. We either confront the stressor or remove ourselves from it (1). The stress is short-lived and allows ample time for the body to recover from the stress response.
After we remove the stressor, the body theoretically seeks to return to a state of calm to re-establish baseline or homeostasis, or perhaps undergo adaptation to tolerate future exposure to that same stressor better. This recovery phase ensures adequate time for each system (e.g., immune system) to complete any needed recovery, replenishment, repair, or adaptation and is illustrated below.
Is stress harmful to the body? Is it something that should be avoided, managed, and reduced – or should it be embraced and utilized to benefit the body?
While no definitive answer exists, there is emerging evidence to suggest that while the manifestation of stress is mainly physiological, it may be the mental perception or interpretation of stress that ultimately dictates whether it is beneficial or harmful.
In a study conducted by Keller and colleagues, 30,000 individuals were tracked to determine their perceptions of stress and its impact upon mortality (Keller, et al., 2012).
As expected, individuals reporting low levels of stress experienced the lowest levels of mortality. In contrast, those experiencing high levels of stress demonstrated the highest risk of mortality, but the interesting discovery lay with the perception of how stress affected the body.
Those who did identify high levels of stress, but also believed that stress was not harmful to the body demonstrated similar mortality rates to those experiencing low levels of stress. Although this study faced some scrutiny, it paved the way for other studies that examined the same notion of mental perception as a key indicator of the effects of stress.
To better understand this difference, it may be helpful to first review key stress-response mechanisms. Our biological stress response was designed for survival and is regulated by both the neural and endocrine (hormonal) systems.
The nervous system is a rapid-acting, but short-livedcommunication system that functions by transmitting nerve impulses – it reacts very quickly to stimuli, but its effects do not last very long (e.g., the sudden, short-lasting elevation of heart rate when startled).
The endocrine system is a slower-acting, but longer-lasting communication system that functions by hormonal action – it is activated more slowly (sometimes by nerve activity) and its effects may last longer (e.g., the sustained elevation of heart rate during a 60-minute run).
Our ancestors’ primary stressors involved a fight for survival or to the death against a predator or aggressor and the nature of the stress was an intense, acute physiological response (Figure 1).
However, after this brief, but stressful encounter, what followed was ample recovery to return to baseline (state of calm – parasympathetic or PNS dominance).
This allowed each physiological system (e.g., immune system) time to restore and regenerate itself after fighting to maintain homeostasis.
By contrast, today’s stress generally involves lower-intensity, sustained psychological stressors that sometimes never go away, but accumulate (Figure 2).
For example, you might sleep through your alarm and wake up in a panic late for your meeting, skip breakfast, get delayed by a slow commute, arrive late for a presentation, get reprimanded by your boss, then finally make it to your office whereupon you receive a call that your child is sick and needs to be picked up from school – sound familiar?
These sustained stressors, although smaller individually, accumulate and deny the body that needed time to repair, recover and replenish.
Nonetheless, in either situation (ancestors v. present-day) the body activates its stress response in similar ways, albeit it at different intensities. And while we are familiar with many responses (e.g., increased heart rate and blood pressure, mobilization of stored fats, increased sweat rates), we may be unaware of others that merit concern (Table 1).
For example, elevated levels of epinephrine enhance blood clotting ability by increasing platelet adhesiveness (5). By design, this might be needed to stop one from bleeding to death during a survival fight, but think about this sustained effect upon cardiovascular health.
Ever wonder why you get dry mouth when nervous, why a dog urinates when scared or why you need to run to the bathroom before a big race?
Consider our need for survival – during a stress response, specific systems require additional resources, essentially borrowing from other systems deemed unnecessary during the ‘fight-or-flight’ response (e.g., reproduction, growth, maintenance).
In other words, some systems automatically shut down to provide the needed resources and energy to the critical systems and locations to facilitate survival (e.g., muscles, skin for thermoregulation). An example of this is saliva and digestive enzyme release in the mouth, stomach, and upper GI to facilitate chewing, digestion, and absorption shut down.
In contrast, the lower GI and bladder’s smooth muscle contractility become activated to void unnecessary urine and fecal matter that may slow you down in the event you need to run to survive. We list many of these allocations or resources in the table below.
Events Activated
Events Inhibited
Increased cardiopulmonary responses
Increased vessel dilation in the needed location
Increased mobilization of fuels
Increased blood clotting ability
Increased large intestinal contractility
Increased bladder contractility
Increased immune function – short-term
Increased sweat rates
Decreased salivary and digestive enzyme secretion, and digestion
Decreased stomach/small intestinal contractility
Reduced pain perception (analgesia)
Reduced growth, repair, and maintenance
Decreased reproduction capacity
Immune function – sustained long-term
While these events are undoubtedly tolerable for a brief period (e.g., workout), think about these events’ consequences during a sustained bout of stress.
For example, blood clots more rapidly during an acute episode of stress to prevent excessive bleeding, but think to the health risk of a stroke or embolism if this effect lasted indefinitely?
Cortisol is an essential hormone released from the adrenal gland in response to stress and provides many benefits:
These events are modulated by and during the presence of cortisol under acute bouts of stress. Now, consider how exposure to stress has changed in humans living today. We have shifted from experiencing infrequent, acute, and short bursts of stress followed by periods of recovery to a lifestyle of sustained episodes of stress that do not include periods of recovery, as illustrated below.
Consider the effects of sustained, elevated cortisol levels on the body’s physiological systems. Many of our planned interventions with clients and athletes focus on controlling appetite, increasing metabolism and fat utilization, building muscle mass, and reducing abdominal fat and overall body fat.
However, under sustained stress and elevated cortisol levels, the actions of many of the hormones responsible for these desirable events are impeded or even inhibited, including:
Furthermore, stress coupled with elevated cortisol can trigger an increased desire to eat given cortisol’s impact upon neuropeptide Y, a neurotransmitter in the brain that regulates appetites.
What follows eating is an elevation of insulin, which acts to inhibit fat metabolism within the body, another undesirable event.
What stress-coping mechanism can you employ to help reduce your client’s stress levels? Many different techniques exist that demonstrate varying levels of success and while they should all be considered, select the one(s) most appropriate for your client(s) (7). Examples include:
Deep Breathing (also known as paced breathing; belly, abdominal or diaphragmatic breathing):
Mindful Techniques:
Body Sensation Awareness:
Stored Energy Release:
Reprioritization:
Social Support:
Predictive Information:
Sense of Control:
Cognitive Flexibility:
In closing, we may hear that stress kills. Still, perhaps a more appropriate interpretation is that it is our inability to accommodate or allow appropriate recovery from stress, considering our naturally-designed stress response, and how we perceive the impact of stress upon our lives that is becoming the problem.
As fitness experts, perhaps it is time to retrain how we approach the subject of stress in our programming and exercise selection for clients.