Week 4 - Hydration Flashcards
How much does water make up of the body?
Adult body = 50-60%
Lean body masses - 75%
Fat mass - 5-10%
What are the functions of hydration?
Nutrient Transport
Protection
Temperature Regulation
Biomechanical Reactions
Medium for Reactions
What is the total body water volume?
42L of 60% of body mass
How does sweat rates change at differing running intensities
As pace and heat stress conditions increase so does sweat rate
What is it known as when there is a negative water balance
Dehydration or hypohydration
What is net body water balance
The difference between total water intake and total water loss
What is dehydration
when body water volume is at a greater deficit than normal fluctuation
How can body mass changes indicate water balance changes?
Change in body mass indicates helps determine changes in body water. >2% body mass reduction = 90%
chance that body water deficits are sufficient
to be classed as dehydration
Why do we sweat
Response to an increase in body temperature in an attempt to cool down the body. Its done by the hypothalamus detecting increase in body temp this then results in increase blood flow to skin and initiates the sweating response
What is evaporative cooling
sweat evaporates from your skin, and as it does, it takes heat away with it, cooling you down. 1L sweat evaporated wil remove 573kcal from the body
During periods of high sweat rates drinking will often lead to body water deficit
Sweat loss
water loss from water component of blood (plasma) = decreased plasma volume and blood volume
Sweat is hypotonic compared to plasma, therefore plasma osmolality increases
What leads to dehydration?
Largely due to inadeuqate fluid intake relative to fluid losses, and during exercise fluid losses are largely attributable to sweating
What are the main mechanisms to control body temp?
Sweating and evaporative heat loss to help prevent the development of hyperthermia
How does hypohydration impair exercise?
1-2% minimal impact
2-3% may degrade aerobic performance, deteriation of sport specific skills, minimal impact on sprint running and cognitive function (without heat stress) and reduced cognitive function (with heat stress)
>3% impaired cognitive function
3-4% Minimal impact on muscle strenght and power
