EXERCISE PHYL FINAL

What is WBGT?

Wet Bulb Globe Temperature (WBGT), index used to determine environmental heat stress

What does WBGT measure?

Environmental heat stress by accounting for temperature, humidity, radiant heat, and air movement

What tool is used to measure WBGT?

Sling psychrometer

How is a sling psychrometer used?

Contains two bulbs: a dry bulb and a wet bulb

What are the two bulbs in a sling psychrometer?

Dry bulb and wet bulb

What is the least severe heat illness?

Heat cramps

What are heat cramps?

Locking up/spasms of muscles caused by sodium loss and dehydration, accumulation of fluid in muscle cells, or both

What causes heat cramps?

Sodium loss, dehydration, accumulation of fluid in muscle cells, or both

What is heat exhaustion?

Moderately severe heat illness where thermoregulatory mechanisms still function but cannot dissipate heat quickly enough, core temp <39°C

What core temperature is associated with heat exhaustion?

<39°C

Who is most susceptible to heat exhaustion?

Unfit or unacclimated people

How is heat exhaustion treated?

Rest in cooler environment, elevate feet, salt water ingestion, or IV fluids if unconscious

What is heat stroke?

Life-threatening heat illness characterized by core temp >40°C and altered mental status

What core temperature defines heat stroke?

40°C

What mental changes occur with heat stroke?

Altered mental status, confusion, unconsciousness

Can sweating stop during heat stroke?

Yes

What is the most effective treatment for heat stroke?

Whole body immersion in cold water

What are other treatments for heat stroke?

Temperate water immersion and wrapping body in cold sheets with vigorous fanning

What are the four mechanisms of heat transfer?

Conduction, convection, radiation, evaporation

What is conduction?

Heat transfer through direct molecular contact with an object

How important is conduction during exercise?

Negligible source of heat transfer during exercise

What is convection?

Heat transfer through motion of gas or liquid across a heated surface

How does air movement affect convection?

Greater movement of air or water increases heat transfer rate

What happens if air temperature is cooler than skin temperature?

Heat transfers from skin to air resulting in heat loss

What happens if air temperature is warmer than skin temperature?

Body gains heat from environment

What is convection important for at rest; what conditions are needed?

Constantly removes metabolic heat generated at rest and during activities of daily living if air temp is lower than skin temp

What is radiation?

Heat given off or accepted as infrared rays

How much heat is lost by radiation at rest?

~60%

How much heat is lost by radiation during exercise?

~5%

What is a major source of radiant heat gain?

The sun

What is evaporation?

Heat loss through vaporization of sweat from skin

What is the primary avenue for heat dissipation during exercise?

Evaporation

How much heat loss during exercise occurs through evaporation?

~80%

How much heat loss at rest occurs through evaporation?

10-20%

When is evaporation the only cooling mechanism?

When air temperature is close to skin temperature

Which heat transfer mechanism only works in one direction?

Evaporation

What is dehydration?

Decrease in plasma volume and increase in osmolality

What stimulates thirst and ADH release?

Dehydration

What is hypohydration?

Decrease in plasma volume only

What causes hypohydration?

Sweating, blood loss, fluid shifts

What cardiovascular effects occur with hypohydration?

↓ stroke volume and ↑ heart rate

How long does heat acclimatization take?

~14 days of exposure to heat

What is the first/fastest adaptation to heat acclimatization?

Increase in plasma volume

What cardiovascular effects result from increased plasma volume during heat acclimatization?

↑ venous return → ↑ stroke volume → ↓ heart rate and reduced perceived exertion

What thermoregulatory changes occur after initial heat acclimatization?

More blood sent to skin, reduced core temperature, maintain lower core temp in same environment

How does sweating change with heat acclimatization?

Sweating starts sooner, sweat rate increases, sweat becomes more dilute

How does aldosterone affect sweat composition, and where?

Promotes NaCl reabsorption in sweat ducts and kidneys

Which electrolytes are not effectively reabsorbed in sweat?

K+, Mg2+, Ca2+

What is poikilothermic?

Condition where body can no longer regulate its own body temperature

At what temperature can poikilothermia occur?

~30°C (86°F)

How does aging affect thermoregulation?

Reduces skin blood flow and vasoconstriction response to cold exposure

Why may older adults struggle with thermoregulation?

Blood vessels may not maintain constrictor tone effectively

What is cold habituation?

Desensitization or dampening of normal response to cold stress

What is the metabolic pattern of cold adaptation?

Greater heat production, more pronounced shivering, and increased non-shivering thermogenesis

What is the insulation pattern of cold adaptation?

Augmented vasoconstriction in response to cold and possibly increased subcutaneous fat thickness

How do Ama divers adapt to cold?

They exhibit all 3 types of cold adaptation patterns

What substrate is primarily relied on in cold environments?

Carbohydrates

Why are carbohydrates relied on in cold environments?

Rapid ATP production and support for shivering thermogenesis

What happens to the oxyhemoglobin dissociation curve during acute altitude exposure?

Shifts left (higher O2 at lungs; less at tissues)

What does a leftward shift of the oxyhemoglobin curve mean?

Hemoglobin has greater affinity for oxygen at lungs but releases less oxygen to tissues

Why does altitude cause respiratory alkalosis?

Hyperventilation blows off CO2, increasing blood pH

How does altitude affect oxygen delivery to tissues?

Less O2 unloaded to mitochondria and muscles

What fuel source reliance increases at altitude?

Anaerobic metabolism and glycogen use

What is the least severe altitude illness?

Cheyne-Stokes breathing

What is Cheyne-Stokes breathing?

Cycle of hyperventilation followed by hypoventilation/apnea due to changing CO2 and O2 levels

What causes hyperventilation at altitude?

Low PPO2/hypoxia

What causes hypoventilation during Cheyne-Stokes breathing?

Low PPCO2/hypocapnia

What is hypoxia?

Decrease in oxygen delivery to tissues

What is Acute Mountain Sickness (AMS)?

Common altitude illness developing 6-12 hours after ascent, peaking at 24-48 hours

At what altitude is AMS common?

2400-3000m

What are symptoms of AMS?

Dizziness, fatigue, nausea, vomiting, headache

What causes symptoms of AMS?

Fluid retention increases intracranial pressure and lung swelling, impairing O2/CO2 exchange

How can AMS symptoms be minimized?

Ascend slowly, descend to sleep, hydrate, eat high-carb diet, acclimate for 3-7 days

What is High Altitude Pulmonary Edema (HAPE)?

Pulmonary edema caused by hypoxia-induced pulmonary vasoconstriction and capillary leakage

What happens to capillaries during HAPE?

They distend and leak fluid causing edema and clot formation

What are symptoms of HAPE?

Shortness of breath, coughing, fatigue, cyanosis(blue lips), confusion

How is HAPE treated?

Supplemental oxygen and immediate descent

What is High Altitude Cerebral Edema (HACE)?

Severe altitude illness involving swelling in cerebral cortex due to distended capillaries

At what altitude does HACE commonly occur?

4300m

What are symptoms of HACE?

Confusion, lethargy(exhaustion), ataxia (muscle uncoordination), unconsciousness, death

How is HACE treated?

Same as HAPE: supplemental oxygen and immediate descent

How do kidneys respond to altitude?

Excrete bicarbonate and retain H+ to compensate for respiratory alkalosis

Why do kidneys excrete bicarbonate at altitude?

To buffer blood and restore pH toward normal

What hormone increases RBC production at altitude?

Erythropoietin (EPO)

What respiratory changes occur at altitude?

Hyperventilation, increased tidal volume, respiratory alkalosis

What stimulates ventilation at altitude?

Low PO2 stimulates carotid chemoreceptors

Why does dehydration occur more easily at altitude?

Increased insensible water loss through respiratory tract

What happens to plasma volume at altitude?

Decreases

Why does plasma volume decrease at altitude?

Respiratory water loss and diuresis/ANP

What cardiovascular changes occur at rest/submaximal exercise at altitude?

↓ plasma volume → ↓ stroke volume → ↑ heart rate → maintain cardiac output and VO2

What cardiovascular changes occur during maximal exercise at altitude?

↓ HRmax → ↓ SV → ↓ Qmax → ↓ VO2max

Why is HRmax reduced at altitude?

Body limits HRmax to protect heart under low oxygen conditions

What happens to aerobic performance at altitude?

Impaired/decreased

What metabolic changes occur at altitude?

Shift toward anaerobic/glycolytic metabolism and increased carbohydrate reliance

How does BMR (basal metabolic rate) change at altitude?

Increases due to increased thyroxine and catecholamines

What is the lactate paradox?

Expected lactate increase at altitude but observed lactate decreases after acclimation

What are characteristics of highlanders?

Higher hematocrit, larger hearts/lungs, more capillaries, greater O2 carrying capacity, better coronary circulation

What is polycythemia?

Increased RBC count/hematocrit

How much greater is oxygen carrying capacity in highlanders?

~28% more than lowlanders

What body type characteristics are common in highlanders?

Long torso and short legs