Table 2.

Physiological stress response to heat.

Physiological response	Explanation
Increased heart rate	High temperatures cause blood vessels to dilate, leading to an increased heart rate as the body attempts to cool down. This heightened cardiovascular activity is part of the body's thermoregulation mechanism, aiming to redistribute heat and maintain internal temperature equilibrium. 66 The increased heart rate is intended to enhance blood flow to the skin's surface, facilitating heat dissipation through sweating. 67 However, prolonged elevated heart rate due to heat stress can strain the cardiovascular system over time. 68
Increased respiration rate	Heat stress can elevate respiration rate as the body attempts to release excess heat. Faster and deeper breathing facilitates heat exchange by expelling warm air and taking in cooler air, aiding temperature regulation. 69 , 70
Dehydration	Heat accelerates fluid loss through sweating, potentially leading to dehydration and affecting cognitive function. Sweating is the body's primary cooling mechanism during heat exposure. 71 As sweat evaporates, it carries away excess heat, but this process also results in the loss of vital fluids and electrolytes. 72 Dehydration can impair blood circulation, decrease cognitive performance, and intensify feelings of fatigue and irritability. Severe dehydration can escalate into a medical emergency, warranting immediate attention and fluid replacement. 73
Vasodilation	Blood vessels expand to dissipate heat, diverting blood flow from vital organs, which can impact cognitive and physical performance. Vasodilation is the body's response to elevated temperatures, designed to direct blood toward the skin's surface for heat dissipation. 74 However, this redirection can lead to reduced blood supply to essential organs, potentially affecting their optimal function. This diversion of blood flow can contribute to decreased cognitive performance, impaired decision‐making, and reduced physical capabilities, ultimately impacting overall well‐being. 75
Electrolyte imbalance	Excessive sweating can disrupt electrolyte balance, affecting nerve and muscle function and contribute to fatigue. Sweating not only results in fluid loss but also leads to the depletion of essential electrolytes, such as sodium, potassium, and chloride. 76 Electrolytes play a crucial role in maintaining proper nerve conduction and muscle function. Imbalances can lead to muscle cramps, weakness, and cognitive disturbances. Addressing electrolyte imbalances becomes crucial to mitigate fatigue, support cognitive clarity, and maintain overall physiological stability. 77
Cognitive impairment	Heat‐induced stress can impair cognitive function, affecting memory, attention, and decision‐making abilities. Prolonged exposure to high temperatures can trigger a stress response in the body, leading to the release of stress hormones such as cortisol. 78 Elevated cortisol levels can impair cognitive processes, including memory formation, attention span, and complex problem‐solving. Heat‐induced cognitive impairments can hinder daily tasks, exacerbate stress, and contribute to a sense of mental strain and frustration. 79
Increased perceived exertion	Physical tasks may be felt more challenging in hot conditions, leading to a perception of increased effort and fatigue. High temperatures can impose additional strain on the body during physical activities. 80 As the body works to dissipate heat and maintain internal temperature, individuals may perceive physical tasks as more demanding than usual. This increased perception of effort can lead to feelings of fatigue and exhaustion, limiting the motivation and ability to engage in daily activities and potentially contributing to decreased overall physical and mental well‐being. 78
Enhanced risk of heat‐related illnesses	Heat exhaustion and heatstroke can result from prolonged exposure, causing confusion, disorientation, and anxiety. Prolonged exposure to high temperatures without proper mitigation measures can elevate the risk of heat‐related illnesses. 81 Heat exhaustion is characterized by symptoms such as confusion, dizziness, nausea, and weakness. Left untreated, heat exhaustion can escalate to heatstroke, a life‐threatening condition marked by elevated body temperature, confusion, disorientation, and potential damage to internal organs. The onset of these heat‐related illnesses can trigger anxiety and distress, further highlighting the significant implications of high temperatures on mental health. 82