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From the previous lesson on anatomy and physiology, recall that the nervous system and the endocrine system work together in the body’s fight-or-flight response to a stressor. The acute response of these body systems was explained in the example of encountering a bear on a hike. But what happens when stress continues for longer periods of time?
To accurately understand the stress response, it’s important to first look back into the origins of research on stress. Hans Selye (1907–1982) was a Hungarian Canadian doctor of endocrinology and was a fundamental researcher in the science of stress and the stress response. Selye did not set out to research stress—his initial discovery was an accident. He was researching the effects of injected hormones in rats and found that many of the rats became sick after receiving the injections, irrespective of whether the injections contained hormones or were a neutral placebo. It turned out that the trauma of being handled and injected led to high levels of sympathetic nervous system arousal in the rats, and eventually to health problems like enlarged adrenal glands and ulcers. Selye continued to experiment by putting the rats in environmentally stressful situations, such as cold temperatures or a continuously running treadmill, and found that the rats developed the same kinds of negative health effects (Tan & Yip, 2018). Selye coined the term “stressor” to label a stimulus that had this type of effect on the body.
Based on his initial research on stress, Selye proposed a pattern of response to stress that he called the general adaptation syndrome (GAS), which consists of three stages—alarm, resistance, and exhaustion.
In GAS, the first encounter with stress results in an alarm reaction. This occurs when we first perceive something as stressful, and then the body initiates the fight-or-flight response, as discussed in the previous lesson, “Anatomy and Physiology of the Stress Response”. In the alarm stage, the body first mobilizes resources to react to the stressor. For example, the epinephrine released by the adrenal glands heightens your alertness, and stored glucose is released into your bloodstream to be a quick source of energy.
If the perceived stress continues, the body systems that respond to stress stay activated in an effort to offset the stress and maintain homeostasis. This stage has one of two outcomes—either the body will adapt to the stress, or the body will become depleted and enter the next stage. If the body adapts to the stress, it returns to a more normalized state, counteracting the sympathetic nervous system activation. Adaptation also means that repair and storing energy can occur because the body is not on high alert, mobilizing all its resources to handle the stressor. However, if the stress continues and the body becomes depleted, it enters the next stage.
In the exhaustion stage, the body’s resources are depleted and worn out from prolonged exposure to stress. For example, the adrenal glands can start to fatigue, producing less cortisol. The resulting wear and tear will suppress the immune system and cause bodily functions to deteriorate. This can lead to a variety of health issues and illnesses, such as heart disease, digestive problems, and ulcers. A person might also start to show physical symptoms from the alarm stage again, such as sweating, increased heart rate, and loss of appetite. In addition, a person in the exhaustion stage not only shows physical signs of stress but mental and emotional signs of stress as well. They might be very irritable, exhibit a lot of anxiety, or feel mentally fatigued.
Hans Selye’s research that led to the concept of GAS demonstrated that stress may be debilitating if it is continuous. Our bodies and minds seem to have evolved to cope well with sudden and brief stressors, like escaping from a predator. However, we do not seem to be designed well to handle chronic stress, even if it is mild. Our society has created many conditions that produce chronic stress and are associated with stress-related illnesses. We have time pressures, work pressures, achievement pressures, relationship pressures, crowding, noise, traffic, crime, and too many things to do in too little time. It is this detrimental effect of ongoing stress that underlies the concept of GAS and the concepts of stress-induced health problems.
IN CONTEXT
Research on the COVID-19 pandemic demonstrated a real-life, large-scale application of GAS. For example, the initial stages of the pandemic caught people off guard and induced an alarm reaction as people’s homeostasis was threatened (Quaglieri et al., 2021) in ways such as mask mandates and social distancing, which disrupted the routines of pre-pandemic life. As the pandemic stressor persisted, people’s perceived stress scores increased as part of the resistance and exhaustion phases (Quaglieri et al., 2021).
It is important to note, however, that GAS conceptualizes stress based only on the body’s physical responses. It does not take psychological factors into account, such as perceptions or interpretations of stressors. Nevertheless, Selye’s model has significantly impacted the field of stress research because it offers a general explanation for how stress can lead to physical damage and disease, which will be discussed in the next lesson.
While our discussion has primarily focused on types of stressors that we would consider negative, like a surprise encounter with a bear or everyday time management hassles, not all stress is automatically bad. The stress response can be lifesaving in some situations. The nerve chemicals and hormones released during stressful times provide preparation to face a threat or flee to safety. When you face a dangerous situation, your pulse quickens, you breathe faster, your muscles tense, and your brain uses more oxygen and increases activity—all functions aimed at survival. In the short term, small amounts of stress can even boost the immune system.
Some stressors can be predominantly positive. Consider something like playing in a sports tournament or starting a new job. These are things we may be happy and excited about but can still be stressful. Regardless of the type of stress, our bodies go through GAS in a predictable way. Perhaps we will continue winning in the sports tournament and continue playing opponents. If we don’t have enough time for rest and recovery, our body can’t adapt and may enter the exhaustion phase, where performance suffers because of overtraining. Conversely, perhaps in our new job, we adapt to the new roles and responsibilities and our body returns to a balanced state.
Based on this, it is also important to understand that the body’s response to stress is inherently neither good nor bad; it is an adaptation reaction to try and maintain homeostasis. Selye introduced two terms to differentiate types of stress. Distress is a stress response initiated by stressors that are overall negative or unpleasant, while eustress is a stress response initiated by stressors that are overall positive challenges to our personal growth (Bienertova-Vasku et al., 2020).
EXAMPLE
A person could be a busy high-ranking executive, a surgeon working under high pressure, or an athlete doing strenuous exercise without experiencing negative stress-related symptoms. What is important is that the person enjoys the challenge and also has adequate recovery.What makes a stressor a source of distress or eustress can depend on the context and personal perception.
EXAMPLE
Public speaking is widely considered to be a source of anxiety and stress for many people, even to the point of being one of the most common types of phobias. Giving a speech might provoke the same stress response in two different people (racing heart rate, sweating, etc.), but one person might perceive the experience as threatening and scary, while the other might perceive it as a positive challenge to overcome and do their best.Differentiating whether a stressor is a source of distress or eustress can be a fine line. One research article describes deadlines, where if we have a deadline coming up for an assignment or work task, we may feel distress and anxiety—however, the deadline creates some positive challenges because it motivates us to meet the deadline and accomplish the task (Bienertova-Vasku et al., 2020). Yet, pushing ourselves to meet the deadline may come with feelings of burnout and exhaustion, affecting our health and causing distress. Regardless, the takeaway on stress is that not all stress is bad and that some amounts of stress are necessary and beneficial.
The concept of stress as beneficial is the premise behind the Yerkes–Dodson law, developed in 1908 by psychologists Robert M. Yerkes and John Dillingham Dodson. The Yerkes–Dodson law describes the relationship between arousal and performance. It states that performance increases with physiological or mental arousal but only up to a certain point, beyond which performance decreases. Arousal is defined as a continuum of physiological and psychological activation that mobilizes the body’s resources for activity (Frame & Reichin, 2019). For purposes of our discussion, arousal is similar to stress as far as the effects on the body, such as increased heart rate and blood pressure, and increased release of epinephrine and cortisol.
According to the Yerkes–Dodson law, we all have an optimal level of arousal (stress). If we are under-aroused, we may become bored and seek out something stimulating. If we are over-aroused, our function and performance may suffer as stress becomes excessive and debilitating. Research shows that moderate arousal is generally best. When stress levels reach the highest point of the curve, a person is at their peak performance—feeling energized, focused, and working with maximum efficiency. As seen in the graph below, the Yerkes–Dodson law illustrates this through a bell-shaped curve, and because of this, it is sometimes also called the “inverted-U theory”. Performance increases with arousal (stress) but only up to a certain point. When levels of arousal (stress) become too high, performance decreases.
Just as GAS is a predictable way in which all humans respond to stress, the Yerkes–Dodson law will cause performance to change in a predictable way. We all perform best with some amount of positive stress—however, that amount of optimal stress can be different across individuals, which is the premise of our next topic.
IN CONTEXT
Exercising to boost fitness is an example of applying both GAS and the Yerkes–Dodson law. A person who starts an exercise routine or program for the first time after being relatively sedentary will probably feel fatigued and sore post-exercise in the first few days as the body’s alarm reaction stimulates a response to this new stressor. If the person continues to work out, their body will adapt during the resistance phase. However, the body will need gradual increases in stress to keep adapting and building toward peak performance, as per the Yerkes–Dodson law. But, if the person tries to do too much exercise before their body is ready for it, they risk negative impacts like strains or sprains because of the deterioration in the exhaustion phase of GAS (Mahaffey, 2022).
The theory of individual zones of optimal functioning (IZOF) accounts for individual differences in responding to stress and arousal, acknowledging that not everyone will respond to the same stress level in the same way (Frame & Reichin, 2019). The theory of IZOF was originally developed to be applied to athletic performance. However, it is relevant to our discussion on the stress response as the theory goes beyond sports and performance.
Initial research in IZOF was done on top-level athletes across all kinds of sports by psychologist Juri Hanin, creator of the IZOF theory. In the graphic below, you can see an example of three different athletes based on their IZOF. Athlete 1 with low IZOF performs best with low arousal levels. Athlete 2 with moderate IZOF performs best with moderate arousal levels. Athlete 3 requires moderate to high arousal levels to perform at their best. Interestingly, Hanin found that many top athletes not only performed well with relatively high amounts of stress and anxiety but that they needed those high levels to perform at their best (Ruiz et al., 2017).
The premise of IZOF theory further highlights that stress and arousal are not all bad. Experiencing some anxiety that causes the stress response can help us feel excited and pumped up, motivating us to direct that excitement into actions that will prepare us for performance (Yao & Li, 2022).
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REFERENCES
Bienertova‐Vasku, J., Lenart, P., & Scheringer, M. (2020). Eustress and distress: neither good nor bad, but rather the same?. BioEssays, 42(7), 1900238. doi.org/10.1002/bies.201900238
Frame, M. C., & Reichin, S. (2019). Emotion and sport performance: Stress, anxiety, arousal, and choking. In APA Handbook of Sport and Exercise Psychology, Volume 1: Sport Psychology., Vol. 1. (pp. 219–243). American Psychological Association. doi.org/10.1037/0000123-012
Mahaffey, K. (2022). General adaptation syndrome in fitness explained. National Academy of Sports Medicine (NASM). blog.nasm.org/general-adaptation-syndrome-explained
Quaglieri, A., Lausi, G., Fraschetti, A., Burrai, J., Barchielli, B., Pizzo, A., Cordellieri, P., De Gennaro, L., Gorgoni, M., Ferlazzo, F., Sdoia, S., Zivi, P., Giannini, A. M., & Mari, E. (2021). "Stay at Home" in Italy during the COVID-19 Outbreak: A longitudinal study on individual well-being among different age groups. Brain Sciences, 11(8), 993. doi.org/10.3390/brainsci11080993
Ruiz, M. C., Raglin, J. S., & Hanin, Y. L. (2017). The individual zones of optimal functioning (IZOF) model (1978–2014): Historical overview of its development and use. International Journal of Sport & Exercise Psychology, 15(1), 41–63. doi.org/10.1080/1612197x.2015.1041545
Tan, S. Y., & Yip, A. (2018). Hans Selye (1907-1982): Founder of the stress theory. Singapore Medical Journal, 59(4), 170–171. doi.org/10.11622/smedj.2018043
Yao, Z., & Li, Y. (2022). Preliminary assessment of individual zone of optimal functioning model applied to music performance anxiety in college piano majors. Frontiers in Psychology, 13, 764147. doi.org/10.3389/fpsyg.2022.764147
