KINE 433: Topic 14 Study Guide

What does the term homeothermic imply?

• Internal body temperature is regulated and nearly constant despite environmental temperature changes

• Thermoregulation involves regulation of body temperature around a physiological set point (~98.6 degrees F)

Please describe the difference between acclimation and acclimatization.

Acclimation: short-term adaptation to environmental stressor (days or weeks)

Acclimatization: long-term adaptation to environmental stressor (months or years)

What is core temperature regulated at in humans (in Celsius)?

37 degrees C

At what core temperature will the nervous system and physiological function become inhibited?

Core temperature >40 degrees C inhibits physiological function and impair nervous system

What is the primary reason that CWI is more effective at cooling core temperature than cool air?

CWI can cause heat loss via convection at 26x greater rate than when exposed to similar temperature of cold air

When the SNS initiates VC and VD, which leads to heat conservation and heat loss?

SNS VC → minimizes heat loss

SNS VD → enhances heat loss

Explain the concept of cardiovascular drift (refer to previous Topic lectures, as well).

Blood volume decreases via sweating → SV cannot be maintained (peripheral blood pooling), so HR will continue to increase to compensate this

• Heat, blood viscosity

What is the explanation of CV system overload as a limitation to exercise performance?

Heart cannot provide sufficient blood flow to both exercising muscle and skin

What is the physiological mechanism that creates the limitation to exercise performance (CV system overload)?

The physiological response to exercise in the heat; Impairs performance due to risk of overheating

Who is most at risk for limitation to exercise performance (CV system overload)?

Especially impacts untrained/nonacclimated athletes

During slow and heavy sweating, why do we see a change from very dilute to less dilute sweat concentration?

Light sweating: very dilute sweat given increased time for reabsorption due to slow filtration rate through ducts

Heavy sweating: less dilute (i.e., increased Na+, Cl- loss) due to faster transit to skin

What are the six risk factors to be considered when training in the heat and considering fluid balance?

1. Metabolic heat production

2. Air temperature

3. Ambient water vapor (humidity)

4. Air velocity → wind/breeze

5. Radiant heat sources

6. Clothing

Heat Cramps

• Least serious of three heat illnesses but can include severe, painful cramping of large muscles

• Triggered by Na+ losses and/or dehydration and most common in heavy sweaters

• Prevented by higher intake of Na+ and water

• Cramping also has neurological fatigue component

Heat Exhaustion

• Symptoms: fatigue, dizziness and nausea, vomiting, fainting, weak and rapid pulse

• Caused by severe dehydration

  • Simultaneous blood flow needs of muscle and skin not met due to lower blood volume

• Thermoregulatory mechanisms are functional but become overwhelmed

Heat Stroke

• Life threatening and most dangerous → thermoregulatory mechanism failure

• Characterized by:

  • core temperature >40 degrees C (best measured by rectal temp)

  • confusion, disorientation, unconsciousness

• If untreated, can lead to coma and/or death

• Whole-body cooling ASAP (ex. immediate CWI) + minimal clothing and rectal temp

What is cold habituation?

• Occurs after repeated exposures with no significant heat loss

• Skin VC and shivering blunted; core temperature allowed to drop more

What is the common misunderstanding of windchill and what is index temperature based on?

• Windchill is misunderstood as air/wind temperature, but is air movement

• Index temperature is based on the cooling effect of wind (cooling power of environment)

  • Windchill does NOT change air temperature

  • Increased windchill = higher risk of freezing tissues

At what water temperature (in Celsius) will core temperature cease to remain constant?

Core temperature will remain constant until water temperature <32 degrees C

• Core temperature decrease of 2.1 degrees C per hour in 15 degree C water

How does heat loss increase in cold water?

Heat loss increases in cold water if it is also moving via convection

• Mitigated with exercise

What is the lethal lower limit of core temperature in Celsius?

Lethal lower limit of core temperature is 25-23 degrees C