**2. The "fight-or-flight" response**

Evolutionarily speaking, stress and our ability to respond to it is adaptive and essential for our survival. When presented with a potential threat, the body automatically engages in a series of adaptive physiological processes to maximize survival [11]. Colloquially this process is known as the "fight-or-flight" response. During fight-or-flight, the autonomic nervous system's (ANS) two sub-systems are engaged: the sympathetic nervous system (SNS) is activated, and the parasympathetic nervous system (PNS—responsible for calming and stabilizing the body) is suppressed. The Hypothalamic–Pituitary–Adrenal (HPA) axis is a critical system, producing a cascade of hormones that both maintain and dampen the fight-or-flight response when a threat is presented or removed, respectively.

While fight-or-flight is strictly a physiological response, it can be maintained and stimulated by psychological processes. The degree of activation among the SNS, PNS, and HPA axis is determined by an individual's perception of how threatening the stimulus is, and can be influenced by psychological factors (e.g., threat perception, anxiety, anticipation, perceived control over the situation, etc.) [12]. When a stimulus is perceived as stressful, the hypothalamus releases corticotropinreleasing hormone (CRH), which subsequently triggers the pituitary gland to release of adrenocorticotropic hormone (ACTH). ACTH travels in the bloodstream to the adrenal glands, located above the kidneys, triggering the release of stress hormones glucocorticoids (i.e., cortisol) and catecholamines (e.g., epinephrine, and norepinephrine) [13].

Stress hormones act upon the SNS and PNS, and higher priority survival functions such as heart rate, respiration, energy reserves, and short-term immunity are increased, while lower priority functions for threat response such as reproduction,

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*Physiological Stress Responses Associated with High-Risk Occupational Duties*

gastrointestinal activity, and long-term immunity are suppressed [14]. As a result, prolonged dysregulation of HPA activity can have systemic negative effects on regulatory processes in the body, thus increasing the risk of health conditions.

Cortisol (i.e., glucocorticoids) is a key regulating stress hormone in the human

Cortisol also has important regulatory functions outside times of stress; cortisol

A normal diurnal cortisol pattern indicates individual ability to maintain and return to homeostasis after experiencing stress [16, 18, 19]. However, chronic or repeated stress and subsequent over-activation of the fight-or-flight response can exhaust the HPA axis, resulting in excessive cortisol secretion and eventually, dysregulated diurnal cortisol cycles. Systemically, cortisol influences a wide range of organs and functions including blood pressure regulation and metabolic activity [13, 20]. Thus, long-term, dysregulated cortisol levels significantly increase potential physical and mental illness risks [21]. Physical issues include but are not limited to, compromised immunity, diabetes, hypertension, and cardiovascular disease. Mental health associations include development of depression, anxiety, and psychophysiological PTSD symptoms, such as hyperarousal, and elevated heart rate [22, 23]. Measuring diurnal cortisol patterns, and distinguishing maladaptive patterns and their associated triggers, are critical for identifying potential health

High-risk occupations present a useful framework for studying the effect of chronic stress on health. By definition, high-risk occupations include work that may be disproportionately exposed to hazardous work environments (e.g., construction, materials handling, emergency response, military) [24]. High-risk occupations imply greater exposure to situations considered potentially dangerous, harmful, or threatening, and potentially, chronically elevated stress responses and excessive cortisol release. Studying the effects of stress in high-risk occupations is also important when taking into consideration performance and duties that are expected to be executed when under stress. Occupational stress that influences performance can result in errors, lower productivity, burnout, or workplace injury, affecting not only the individual but straining the infrastructure of their workplace and health resources [25]. While there are many different types of high-risk occupations,

is additionally excreted in a systemic diurnal pattern over every 24-hour period cycle. Among healthy individuals, the diurnal pattern consists of higher levels upon waking, a significant peak around 30 minutes post-waking (i.e., the cortisol awakening response—CAR), steady decline throughout the day, and reaches its lowest point in the middle of the night before again elevating again in the early hours of the

HPA axis cascade. Cortisol potentiates the effects of catecholamines on beta receptors (necessary for impacting peripheral receptors), suppresses immune function, and terminates the fight-or-flight response (via negative feedback loop) [15]. Cortisol is excreted in a dose–response manner to the level of perceived threat by the individual, meaning the greater the perceived threat, the more

*DOI: http://dx.doi.org/10.5772/intechopen.93943*

**2.1 Cortisol**

next day [17].

risks in populations.

**3. High-risk occupations**

cortisol that is excreted [16].

**2.2 Health risks of maladaptive stress responses**

gastrointestinal activity, and long-term immunity are suppressed [14]. As a result, prolonged dysregulation of HPA activity can have systemic negative effects on regulatory processes in the body, thus increasing the risk of health conditions.
