Exercise Physiology 2 Unit 4 Class 1

Where does heat come from during exercise?

~60-70% of energy from muscle contraction is released as heat

Why does core temperature increase during exercise?

Because muscles produce large amounts of heat during metabolism, and not all of it can be removed fast enough.

Why does higher intensity exercise produce more heat?

Higher intensity = more energy use → more metabolic heat produced.

What are the four mechanisms of heat loss?

• Radiation

• Convection

• Conduction

• Evaporation (most important during exercise)

Which heat loss mechanism is most important during exercise?

Evaporation (sweating)

Why is evaporation critical during exercise?

Because it can remove large amounts of heat when sweat evaporates from the skin.

How does humidity affect heat loss?

High humidity reduces evaporation, making it harder to cool the body.

How does wind/air movement affect heat loss?

Increases evaporation and convection → improves heat loss.

What is the difference between core and skin temperature?

• Core temperature = internal body temperature (vital organs)

• Skin temperature = surface temperature

Why is maintaining core temperature important?

Because high core temperature can impair function and lead to heat illness.

How does the body move heat from core to skin?

Through increased blood flow to the skin.

What role does the cardiovascular system play in thermoregulation?

• Transports heat via blood

• Redistributes blood between muscles and skin

Why does skin blood flow increase during exercise in the heat?

To transfer heat from the core to the skin for cooling

What is the “competing demand” during exercise in heat?

Blood is needed for both:

• Muscles (for oxygen)

• Skin (for cooling)

How can increased skin blood flow affect performance?

Less blood available for muscles → decreased performance.

Why is sweating the primary cooling method during exercise?

Because evaporation of sweat removes large amounts of heat.

What factors affect sweat effectiveness?

• Humidity

• Air movement

• Skin exposure

Why is sweating less effective in humid environments?

Sweat cannot evaporate easily because the air is already saturated with mois

What is heat balance?

The balance between heat produced and heat lost by the body.

What happens if heat production exceeds heat loss?

Core body temperature rises.

Compare heat regulation in cool vs hot environments.

• Cool: easier to lose heat

• Hot: harder to lose heat → greater risk of overheating

Compare dry vs humid environments.

• Dry: better evaporation → easier cooling

• Humid: poor evaporation → harder cooling

In which environment is overheating more likely: hot & humid or hot & dry?

Hot & humid (because evaporation is limited)

During exercise in the heat, what happens to skin blood flow, sweating, and core temperature?

• Skin blood flow: increases

• Sweating rate: increases

• Core temperature: increases

What happens to heart rate during exercise in the heat?

Increases (to support both muscle activity and cooling)

Why does heart rate increase more in hot environments?

Why does heart rate increase more in hot environments?

During exercise in heat, what does the body prioritize: muscles or cooling?

Cooling (to prevent dangerous increases in core temperature)

How does the body regulate temperature during exercise?

• Produces heat via metabolism

• Removes heat through radiation, convection, conduction, and mainly evaporation

• Uses cardiovascular system to move heat to skin

• Maintains balance between heat production and heat loss