Podcast
Questions and Answers
What is hyperthermia?
What is hyperthermia?
Which part of the body acts like a thermostat for thermoregulation?
Which part of the body acts like a thermostat for thermoregulation?
What does the Heat Stress Index measure?
What does the Heat Stress Index measure?
Which mechanism of heat loss involves air blowing over the skin's surface?
Which mechanism of heat loss involves air blowing over the skin's surface?
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What role do receptors in the periphery and CNS play in thermoregulation?
What role do receptors in the periphery and CNS play in thermoregulation?
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At what core temperature does serious heat illness typically occur?
At what core temperature does serious heat illness typically occur?
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What external factor significantly influences thermoregulation?
What external factor significantly influences thermoregulation?
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Which mechanism of heat loss is particularly effective when in contact with cold surfaces?
Which mechanism of heat loss is particularly effective when in contact with cold surfaces?
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In which scenario would thermoregulation be most challenged?
In which scenario would thermoregulation be most challenged?
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Which statement about homeotherms is accurate?
Which statement about homeotherms is accurate?
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What physiological response occurs to help dissipate heat during increased body temperature?
What physiological response occurs to help dissipate heat during increased body temperature?
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Which factor contributes to greater heat production in individuals?
Which factor contributes to greater heat production in individuals?
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What is a primary characteristic of heat exhaustion?
What is a primary characteristic of heat exhaustion?
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What is the most dangerous consequence of exertional heat stroke if left untreated?
What is the most dangerous consequence of exertional heat stroke if left untreated?
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Which of the following is NOT a method of heat loss?
Which of the following is NOT a method of heat loss?
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What role does hypohydration play in heat illness?
What role does hypohydration play in heat illness?
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Which temperature measurement is most accurate to assess core body temperature during heat stress?
Which temperature measurement is most accurate to assess core body temperature during heat stress?
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Which of the following describes the effect of fitness level on heat tolerance?
Which of the following describes the effect of fitness level on heat tolerance?
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How does the body primarily lose heat in extremely hot conditions?
How does the body primarily lose heat in extremely hot conditions?
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What symptom is commonly associated with heat cramps?
What symptom is commonly associated with heat cramps?
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What is one potential outcome of excessive heat stress on the body?
What is one potential outcome of excessive heat stress on the body?
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What physiological response does the body initiate when exposed to cold?
What physiological response does the body initiate when exposed to cold?
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What environmental condition predominantly affects endurance performance?
What environmental condition predominantly affects endurance performance?
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Study Notes
KINE 442 - Exercise Physiology
- Course material covers heat and cold stress, relating to exercise.
- Week 14 content focuses on heat stress.
- Lecture 2 covers heat stress.
Heat Stress Overview
- Hyperthermia: An increase in the deep internal body temperature above normal levels.
- Heat stress requires the body to dissipate excess heat from working muscles during exercise.
- 75% of energy from food is released as heat.
- Thermoregulation: The body's ability to maintain a constant internal temperature.
- Humans are homeotherms, unlike amphibians, fish, and reptiles, which allows them to function in varying environments.
- Elevated heat and humidity increase the challenge of heat dissipation.
- Normal core temperature is 37 degrees Celsius.
- Serious heat illness can occur at 41 degrees Celsius.
Thermoregulation
- Receptors in the periphery and central nervous system (CNS) detect temperature changes.
- Peripheral receptors are located in and under the skin and in the peritoneal (abdominal) cavity.
- CNS receptors are in the brain stem and spinal cord, with the hypothalamus acting as a thermostat.
PO/AH Negative Feedback Regulation of Thermoregulation
- The dorsomedial hypothalamic nucleus (DMH) and periaqueductal gray matter (PAG) are involved in the control.
- Warm-sensitive neurons signal the preoptic area of the hypothalamus, increasing core temperature.
- Input from cold receptors also influences temperature regulation.
- Skin vasoconstriction, nonshivering thermogenesis, shivering, and sweating are responses to temperature regulation.
Hypothalamic Control of Body Temperature
- Acute regulation involves various mechanisms, including the cerebral cortex.
- The hypothalamus acts as a thermostat, regulating internal temperature.
- Voluntary responses such as seeking cooler environments, loosening clothing, and drinking cold fluids are part of the regulation response.
- Physiological responses: increased sweating, skin blood flow, and changes to heart rate.
External Factors Determining Thermoregulatory Stress
- Ambient temperature is a critical factor.
- Relative humidity (percent of water vapor in air) affects the body's ability to cool down. Higher humidity makes cooling more difficult.
- Wind speed impacts heat dissipation.
- Heat Stress Index (HSI) combines temperature and humidity to estimate the physiological stress the body experiences.
Mechanisms of Heat Loss
- Convection: Heat loss through air currents. (e.g., swimming, wind).
- Conduction: Heat loss due to direct contact with a surface. (e.g., a cold bath).
- Radiation: Heat loss through electromagnetic waves.
- Evaporation: Sweating vaporizes, drawing heat away from the body. (Evaporative cooling)
Common Consequences of Heat Stress
- Heat Cramps: Muscle cramps due to dehydration and electrolyte imbalances (sodium & potassium).
- Syncope: Fainting caused by excessive peripheral dilation, pooling of blood in the legs, dehydration, reduced cardiac output, or brain ischemia. More common in those not acclimated.
- Heat Exhaustion: Results from heavy sweating, dehydration, sodium loss, and energy depletion. Often confused with heat stroke, it occurs in hot/humid environments. Signs/symptoms may include persistent muscle cramps, weakness, pallor.
- Exertional Heat Stroke (EHS): A medical emergency caused by the failure to dissipate heat after intense exercise; the body's thermoregulatory center is overwhelmed. Symptoms include tachycardia, hypotension, altered mental state, and seizures; core temperature is dangerously high.
- Complications of EHS include lactic acidosis, excessive potassium, acute renal failure, rhabdomyolysis, bleeding disorders, and death.
- Treatment of heat stroke involves rapid cooling.
Factors Affecting Heat Illness
- Fitness Level: Greater fitness generally means less susceptibility.
- Age: Cardiovascular function declines with age.
- Careful considerations of fitness, proper hydration and pre-conditioning are key factors to consider during activity.
Endurance Performance in the Heat
- Heat impacts endurance performance.
- Effective measures to maintain optimal performance include pre-acclimatization/acclimation, hydration, and physical conditioning.
- The Wet-Bulb Globe Temperature (WBGT) index helps predict performance decrements due to temperature, humidity, and solar radiation.
Anaerobic & Strength Performance in the Heat
- Performance in anaerobic and strength activities may be limited by duration of heat exposure.
- Proper cooling and hydration are important factors to performance.
Prevention Strategies
- Acclimation/Acclimatization: Physiological adaptations to an environment. Acclimation is to an artificial environment, Acclimatization is for a natural environment.
- Adaptation timelines vary based on the body system being adapted, with complete adaptation taking 14 days or more.
Hydration
- Sweating cools the body but can lead to dehydration.
- Chronic dehydration may increase heat illness susceptibility.
- Proper hydration is key to performance.
Cold Stress
- Cold receptors in the body's periphery and CNS detect cold and trigger responses designed to conserve body heat. These receptors are fewer in number and are located in the skin, abdominal viscera, and spinal cord.
- Responses to cold stress include vasoconstriction, reduced sweating, increased metabolism, and shivering.
- Physiological adaptations to cold can occur through acclimatization/acclimatization.
Hypothermia
- Hypothermia is a decrease in body temperature that disrupts physiological function.
- There are three stages of hypothermia related to core body temperature and associated physiological consequences.
Performance Responses to Cold
- Cold reduces neuromuscular activity, nerve conduction velocity, and force production.
- Prior cold exposure can have long-term negative impacts on performance.
- Proper cold-weather attire and avoidance of overexposure to environmental cold are key factors in preventing injury.
Cardiovascular and Endurance Performance in Cold Weather
- Submaximal/Maximal exercise oxygen consumption is typically less affected during acute cold exposure, compared to heat stress.
- Exercise-induced bronchoconstriction (EIB) can occur in cold environments in those who have asthma or other respiratory conditions.
- Cold environmental conditions have fewer performance impacts when proper clothing and acclimatization strategies are adopted.
- Pre-cooling can be a performance-enhancing strategy in hot environments.
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Description
This quiz focuses on week 14 content from KINE 442, specifically covering heat stress in exercise physiology. It explores concepts like hyperthermia, thermoregulation, and the body's ability to thermally adapt during physical exertion in varying temperatures. Prepare to test your understanding of how heat impacts exercise performance.
