Lecture 9: Thermoregulation and aerobic exercise Flashcards
Core Body Temperature Increases with Exercise:
- Heat Production from ATP Hydrolysis
=> muscles contract and hydrolyse ATP, produces heat, which raises your core body temperature. - Intensity Dependency
=> At higher intensities (e.g., approaching VO₂ max), the body produces more heat due to greater ATP hydrolysis. - Pre-Exercise Warm-Up
=> Increasing muscle temperature before exercise, through activities like warm-up exercises, improves performance.
=> muscles are more flexible and efficient, which can enhance force production and reduce the risk of injury.
Evaporation as the Primary Heat Dissipation Mechanism:
- To counter the rise in core body temperature, the body relies heavily on evaporative cooling through sweating.
- Sweat evaporates from the skin, taking heat with it, which helps maintain a stable body temperature even during intense exercise.
mechanism:
- The warm blood transfers some of this heat to the sweat on the skin’s surface.
- When the sweat evaporates, it takes the absorbed heat away from the body.
temperature effectiveness:
Ambient Temperature:
- In cooler environments = highly effective because the air can absorb more moisture.
- hot and humid conditions = evaporation rate decreases
=> the air is already saturated with water vapor, making it harder for the body to cool down.
=> body’s heat production exceeds its capacity to dissipate heat
Air Movement:
Wind or air movement enhances the evaporation process by moving the saturated air away from the skin and replacing it with drier air, which can absorb more moisture.
how does Environmental Influence on Exercise Performance:
High Ambient Temperature
Increased Heat Stress: When exercising in a hot environment, the body’s core temperature rises more quickly because the external temperature is close to or higher than body temperature. This reduces the gradient for heat loss between the body and the environment, making it harder to dissipate heat through radiation and convection.
Impaired Cooling: In high temperatures, the body relies more on evaporative cooling (sweating) as other heat loss methods become less effective. However, if the air temperature is very high, sweat may not evaporate efficiently, leading to a risk of overheating.
Impact on Performance: As the body struggles to maintain a stable core temperature, the cardiovascular system is placed under greater strain.
Blood is diverted away from working muscles to the skin to aid in cooling, in attempt to allow more heat to be transferred away => through radiation and convection though less efficient
==> which can reduce muscle oxygenation and nutrients required for endurance, strength and overall performance
Additionally, high body temperatures can lead to fatigue, decreased muscle function, and increased perception of effort, all of which negatively impact performance.
Hot, humid environement :
evaporation rate reduces, cooling effect reduces while core body temperature continues to rise == heat stress
Body’s inability to cool off causes fatigue, CV strain and dehydration == reduced exercise capacity
radiation and convection
Radiation == Direct Emission of Heat
During exercise, as your core body temperature rises, the amount of heat radiated from your body increases. The body radiates heat to cooler objects or the surrounding air if they are at a lower temperature than your skin.
in very hot environments == he effectiveness of radiation decreases because the temperature gradient is reduced or even reversed.
-> your body might absorb more heat from the environment than it radiates away.
Convection == Heat transfer through air, or water movement
Transfers heat away from the body by moving cooler air or water over the skin. It depends on the movement of these fluids and is effective when there is a temperature difference between the body and the environment.
evaporation = Cools the body by converting sweat from a liquid to a gas, which removes heat from the body. It depends on the presence of sweat and the capacity of the air to absorb moisture.
Dehydration and Its Impact on the Cardiovascular System and performance
in an attempt to cool itself through evaporation, it also leads to a loss of body fluids
Increased Respiratory Water Loss: With increased breathing rates during intense exercise, more water is lost through respiration as well.
reduction in plasma volume (Plasma is primarily water, and as the body loses water through sweat, plasma volume decreases.)
==> concentration of red blood cells and other components in the blood increases
==> blood is moe viscous with less plasma volume, affecting circulation
Reduced Cardiac Output:
- Stroke Volume Decrease: Stroke volume is the amount of blood the heart pumps with each beat. When plasma volume decreases, the amount of blood returning to the heart (venous return) is reduced, leading to a lower stroke volume.
- heart rate increases in an attempt to maintain cardiac output (the total volume of blood the heart pumps per minute). This phenomenon is known as cardiovascular drift.
==. the cardiovascular system becomes strained and higher rate of perceived exertion, meaning exercise feels harder.
- lower cardiac output, less oxygen is delivered to working muscles, which can lead to quicker onset of fatigue and a decrease in exercise performance.
: With less blood volume, a reduced pressure within the circulatory system, Reduced blood flow
=> muscles means they receive less oxygen and nutrients, which hinders their ability to sustain prolonged exercise.
Reduced blood flow to the skin compromises the body’s ability to dissipate heat, further exacerbating the risk of overheating.
heat acclimation
: Regular exposure to hot environments can lead to heat acclimation, where the body becomes more efficient at regulating its temperature during exercise.
* increased sweat production
* sweating occurs earlier for a headstart
* sweat is more diluted so more can evaporate while preserving the electrolytes
==> better heat dissipation and improved exercise performance.
