Exam 3 review slides Flashcards
temperature homeostasis
balance between heat gain and heat loss in order to maintain core temperature
normal core temp, low temp, high temp
normal: 37C
low temp: 34C (impaired metabolism and arrhythmias)
high temp: 45*C (protein and enzyme breakdown)
involuntary heat production
- shivering (5x increase)
- action of hormones (thyroxine and catecholamines)
4 ways to dissipate heat
- radiation
- convection
- conduction
- evaporation
changes in humididty result in — in vapor pressure
increases
skin vapor pressure
32 mmHg (the greater the gradient or difference is the greater heat loss)
POAH response to increase in core temp
- cutaneous vasodilation, allowing increased heat loss
- stimulation of sweat glands for evaporative heat loss
POAH response to decrease in core temperature
- shivering and increased norepinephrine release
- decreased skin blood flow via vasoconstriction
exercise intensity and heat production relationship
- positive linear relationship
- heat loss also increases in exercise however it does not mitigate the gains in heat production
Heat index
relative humidity added to air temperature, measure of how hot it feels
physiological concerns with exercising in the heat
- high humidity impairs evaporative heat loss resulting in higher core temp
- increased sweat rate results in higher risk of dehydration
percentage loss of body weight via fluid loss can lead to exercise performance impairment
1-2% body weight loss via sweat
ways to combat dehydration
- increase fluid intake before, during, and after exercise (consume 150-300 ml fluid every 15-20 min)
- consume electrolyte drinks to maintain electrolyte balance
as temperature and humidity goes up…
the body relies on evaporative heat loss more as convective and radiative heat loss become methods for heat gain
most beneficial techniques to mitigate heat gain in hot environments
- cold water immersion
- cooling ice vest
- cooling packs and towels
- ingestion of cold drinks
acclimation
rapid adaptation (days to weeks) to environmnetal change
acclimatization
adaptation over a long time period (weeks to months)
sex and age differences in thermoregulation
- little differences
- only due to deconditioning
cardiovascular dysfunction and impaired exercise performance
- reduced stroke volume
- decreased muscle blood flow
- decreased cardiac output during high-intensity exercise
accelerated muscle fatigue and impaired exercise performance
- muscle glycogen depletion
- decreased muscle pH
- increased radical production
central nervous system dysfunction and impaired exercise performance
- decreased motivation
- reduced voluntary activation of motor units
acclimation and inactivity
-acclimation is lost within days of inactivity or no heat exposure
-significant decline in 7 days, complete loss in 28 days
how to adapt to heat
- repeat bouts of exercise in hot environments
physiological adaptations during heat acclimation (5)
-10-12% increase in plasma volume to maintain blood volume, stroke volume, and sweating capacity
- earlier onset of sweating and higher sweat rate
- reduced skin blood flow
- reduced sodium chloride loss in sweat, reduced risk of electrolyte disturbance
- reduced risk of heat injury due to the synthesis of heat shock proteins
Adapting to heat and its impact on HR and core temp
- decreased HR with acclimation due to stroke volume maintenance and improved ability to mitigate heat gain
exercise in cool for heat acclimation
it works but less than training in the heat
partial pressure
- % of O2, CO2, and N2 in the air is same
- there is lower partial pressure of O2, CO2, and N2 at higher altitudes
hypoxia
low partial pressure of O2 (at altitude)
Normoxia
normal PO2 (sea level)
Hyperoxia
high PO2 (below sea level) (artificial?)
Altitude and short term anaerobic performance
- lower PO2 has no effect on performance
- lower air resistance may improve performance depending on event (long jump)
altitude and long term aerobic performance
lower PO2 results in poorer aerobic performance as it is dependent on oxygen delivery to muscle
altitude and VO2 max
- decreased VO2 max at higher altitude due to lower oxygen extraction
- decreased maximal cardiac output at altitude
Altitude, submax workload, HR, ventilation
- higher HR due to reduction in oxygen content in blood
- increases in ventilation due to reduction of O2 molecules per liter of air
Process of altitude acclimation
- kidneys produce erythropoietin (EPO) in response to decreased blood oxygen
- EPO in circulation stimulates increase in red blood cells
- increased red blood cells increases oxygen binding and blood oxygen content
- blood oxygen content increases toward sea levels as a result
Does training at altitude increase VO2 max?
- some athletes report gains in VO2 max while others do not
- may be due to different training status or detraining effect as exercise intensity is reduced at altitude
Live High, Train Low theory
- living at high altitudes stimulates an increase in RBC, while still being able to train at high intensity at training sea level results in no detraining effect observed
- must have prolonged exposure to moderate altitude or repeated shorter exposure to high altitude
- (The reverse aims to reduce the negative effects of prolonged altitude exposure; however, it results in little to no change in RBC concentration. VO2 max improvements without RBC increase have been shown due to increased mitochondrial function and buffering capacity however, it is highly debated)
lactate paradox
- at high altitude HR, lactate, and ventilation increases occur
- with acclimation, lactate is reduced due to low levels of plasma epinephrine or muscle adaptations
possible health events with hyperthermia (4)
- heat syncope (headache nausea)
- heat cramps (muscle cramping)
- heat exhaustion (profuse sweating, clammy hands, shallow breathing)
- heat stroke (lack of sweating, flushed skin color, labored breathing, unconscious)
Factors related to heat injury
- Fitness = higher fitness level associated with lower heat injury risk due to higher sweat rates and heat tolerance
- Acclimatization = increases in plasma volume and sweat capabilities, lower HR and body temp response, increases VO2 and CO during hot exercise, best protection against heat injury
- Environmental temperature = convection and radiation heat loss dependent on skin to air temperature gradient
- Hydration = dehydration effect can speed up fatigue and heat injury onset (loss of plasma volume, SV, and CO)
- Clothing = materials can impair evaporative and convective heat loss as well as trap heat at the skin decreasing core-to-skin temperature gradient
- Humidity (water vapor pressure) = evaporative heat loss is dependent on gradient between skin and air and increased humidity decreases that gradient reducing evaporation heat loss
- Metabolic rate = core temperature is proportional to work rate meaning that heat produced will be dependent on how hard the body is working
- Wind = increases both evaporative and convective heat loss due to more airflow over skin
ways for athletes to avoid heat-related problems
- emphasize pre-season conditioning as well as acclimation periods as increases in fitness will improve heat tolerance
-frequent water stops
-schedule events for cooler parts of the day and seasons of the year
risk of heat stress dependent on
- wet bulb globe temperature
- includes measurements of dry bulb temp (air temp in shade), wet bulb temp ( index of ability of evaporative heat loss), and black globe temp (the radiative heat gain in direct sunlight
overload
system is exercised at level beyond what is normally
specificity
training effect dependent on training type, differences in muscles fibers recruited and energy systems used
reversibility
gains and adaptations are lost when overload stimuli is removed
VO2 max and genetics
50% of VO2 max is determined by genetics
exercise to increase VO2 max
- prolonged dynamic exercise at 50-70% or higher VO2 max
- could increase by 15-20%
VO2 max improvements following training
- increases in SV and a-vo2 difference
- increased mitochondria, capillary density, blood flow results in greater oxygen saturation
- short duration training results in SV improvements, long duration training results in greater improvements
endurance training adaptations of fiber type and capillarity
- fast to slow shift in muscle fiber types
- reduction in fast myosin
- increase in slow myosin as well as increased capillarity
- results in greater oxygen diffusion/removal of waste products
endurance training adaptations of mitochondrial density
- Increased mitochondrial density
- Increase # of ADP transporters in mitochondrial membrane
- Improves efficiency of ATP production
- Results in lower O2 deficit at onset of exercise
- Same VO2 achieved at lower ADP levels
- Quicker rise in oxygen uptake
- Results in decreased metabolic strain and lowers lactate production and PC utilization
elements of strength training
- muscle strength
- muscle endurance
-muscular power
hypertrophy
- enlargement of both type i and type ii fibers, greater enlargement of type ii
- attributed to increases in myofibrillar proteins, number of cross bridges, ability to generate force
hyperplasia
- theory that one can increase muscle fiber number by splitting a singular fiber
- limited human research on this
- can be achieved with steroids