wk1 heat and exercise performance Flashcards
what 4 regulators does heat stress cause conflict within
temperature regulation
blood pressure regulation
blood volume regulation/osmoregulation
respiratory regulation
how does heat stress impair endurance performance
reduction in time to exhaustion
progressive decrease in work rates in self-paced exercise
reduced maximal aerobic power (lower vo2 max)
what does heat stress lead to
hyPERthermia
how does heat stress affect cardiovascular function
through redistribution and comp for blood flow - impacts o2 delivery and heat dissipation
how does heat stress affect the central motor drive
influences muscle activation and force production capacity - makes normal work seem harder
how does heat stress affect skeletal muscle function
metabolic demands increase, structural characteristics of the muscle
skeletal muscle autonomic responses
what happens to HRmax under heat stress conditions
it is reached at a lower work rate - coupled with lower SV leads to less cardiac output
what alterations happen in the central motor drive during heat stress
lower afferent input - less muscle activation and force, less voluntary activation and less excitability
lower motivation to exercise - increased total discomfit
what happens when you reach your critical core temp
triggers premature fatigue by reducing your mental drive, acts as a safety break
what problems occur in skeletal muscle functions during heat stress
increased muscle glyc utilization and anaerobic metabolism causing greater accumulation of ammonia and muscle lactate
what is the order of priority of regulation during heat stress exercise
1.blood pressure
2.metabolism
3.body temperature
what does dehydration cause
lower plasma volume
increased plasma osmolality (less diluted blood so more ions than water)
what does plasma hyperosmolality do during exercise
this reduces the sweat rate at any gicen core temp, ultimately lowering evporative heat loss
how does dehydration affect performance
heightens core temperature rapidly
how can single-sprint performances be improved
passive local muscle heating - warm baths/heated blankets
active warm ups
passive heating - elevate core temp by 1c
how can partial heat help anaerobic performances
faster rate of pcr utilisation
greater ATP turnover and adenine nucleotide degradation
accelerated muscle fiber conduction velocity
what temp is best to improve repeated sprint performance
lower than 38.5c
how can elevated core temp impair repeated sprints
impaired CNS
reduction in co2 and o2 transport
how to optimise during heat stress
weeks - training, acclimatization
hours - hydration, pre-cooling
during - clothing, hydration, pacing, cooling
what is the difference between acclimation and acclimatisation
acclimation = artificial exposure
acclimatisation = natural exposure
how does acclimatizing help
larger reduction in body temp during exercise
increases onset threshold, sensitivity and max capacity of sweating and skin blood flow responses
increases total body water
reduces loss of ions through sweat
how does acclimation increase total body water
rapid increase in plasma volume expansion
increase secretion or renal sensitivity to fluid regulation hormones (aldosterone, vasopressin and albumin)
what adaptions occur when prepared for heat stress
higher blood volume
lower hr at rest and during exercise
increased stroke volume
all reduce cardiovascular strain during exercise
what are heat shock proteins
heat acclimation increases HSP’S, these provide cytoprotection - protect and accelerate repair from heat stress
how does heat adaption help the metabolism
glycogen sparing
increases lactate threshold
reduces lactate conc during exercise - improves economy
what are the classic markers for heat acclimation
plasma volume expansion
lower core temp
lower hr
increased sweat
increased thermal comfort
what is the difference between short and long term heat acclimation
short term has higher excitability in terms of mechanisms that help deal with heat tress however long term has higher efficiency
what temps does performance decrement over a long period of time
anything over 10c for longer than 120mins will cause a decreased performance
how else does heat acclimation help total body water
sweat losses less Na, Cl and K
increases renal retention of water and electrolytes
changes oncotic pressure and drawing fluid into the intravascular space
when does acclimation set in
after 1 week of acclimation effects will be apparent, continous will obvs have more effect
