Environmental effects Flashcards
What is the definition of altitude?
Height above sea level
What happens to barometric pressure as altitude increases?
Decreases
What happens to the partial pressure of oxygen as altitude increases?
Decreases
What altitude is counted as high?
Anything above 1500m
What happens to the diffusion gradient as altitude increases?
Decreases so less diffusion of oxygen occurs
What happens to partial pressure of oxygen in alveoli as altitude increases?
Decreases (called hypoxia)
What does a decrease in oxygen partial pressure do to the diffusion rate?
Decreases rate as decreased oxygen available decreases diffusion gradient
What happens to the oxyhaemoglobin saturation at high altitudes?
Decreases saturation (external respiration)
What does a decrease in haemoglobin saturation cause?
Less oxygen to be transported to muscles (decrease in arterial partial pressure of oxygen)
What does a decrease in the diffusion gradient during internal respiration cause?
Less dissociation of Oxygen from haemoglobin so less Oxygen available to muscles
At high altitudes how does the body maintain oxygen intake?
Increasing frequency, tidal volume and minute ventilation at rest and exercise
What does the cardiovascular system respond to when at altitude?
A low partial pressure of oxygen
What happens to plasma volume in response to low partial pressure of Oxygen?
Rapidly decreases the volume (25% in 2/3 hours) to increase density of rbc’s (haematocrit) to increase oxygen transport
What does a decrease in plasma volume cause?
Decrease in stroke volume due to decreased plasma which increases heart rate to maintain cardiac output
What happens to the maximal cardiac output at high altitude?
Decreases as decreases maximum stroke volume and heart rate
What are the net effects of increased altitude?
Decrease VO2 max/oxygen capacity.
Decrease max aerobic performance as altitude increases.
Increased use of anaerobic energy systems, increasing OBLA and early fatigue.
Decrease intensity/duration of work
How much does VO2 max decrease by?
10% for every 1000m above 1500m
What events are most effected by altitude?
The more aerobic the event the more the athlete is effected
What events most need acclimatisation?
Aerobic
Eg 5,000-10,000m. Team games
What events most suffer from reversibility at high altitude?
Aerobic, can’t train at high enough intensity / for a long enough duration to keep adaptations
What is the effect of altitude on high intensity low duration events?
No effect/improve
Eg Javelin/sprints are improved as thinner air density so less air resistance/drag on sprinter / equipment
How does altitude effect middle distance (800m) performers that use FOG fibres?
Decrease as altitude increases lactic acid, OBLA and therefore they fatigue quicker
What is the definition of acclimatisation?
Process of adapting the body to perform in a new environment (high altitude)
What does acclimatisation prepare the body for?
To perform with a lower partial pressure of oxygen (at above 1500m)
(Won’t fully compensate and won’t regain original sea level VO2 max/performance)
How does the length of time needed to acclimatise change as altitude increases?
More time needed as altitude increases.
What is the optimal acclimatisation level?
2200m for 28 days
What are the generic guidelines for acclimatisation?
Decrease intensity for first few days (60-70% of sea level intensity)
Increase to full intensity as event approaches (2 weeks for full acclimatisation)
Rest days needed if at more than 3000m
What is the extra generic guideline for team / endurance sports?
Weeks of high intensity training at sea level first to increase VO2 max before going to altitude.
Allows performers to compete at altitude with higher intensity than those that don’t do this.
What are the cardiovascular benefits of acclimatisation?
Release of EPO within 3 hours (peaks at 24-48 hours)
Increase of red blood cells.
Breathing rate and minute ventilation stabilise but are still above sea level values
What are the respiratory benefits of acclimatisation?
Stoke volume and cardiac output decrease as gaseous exchange becomes more efficient with low partial pressure of oxygen.
Lower cardiac output during sub-max intensity.
Heart rate remains elevated at rest and during exercise
What are the other benefits of acclimatisation?
Reduced: Altitude sickness Headaches Breathlessness Poor sleep/appetite
What is the best timing of arrival if you don’t have time to acclimatise?
Arrive as late as possible and compete within 24 hours
Why would someone arrive as late as possible and compete within 24 hours at high altitude?
If no time to acclimatise then arriving late means you decrease acclimatisation but perform before the affects of altitude become too great.
Acute altitude effects increase/worsen after 24 hours.
No time for reversibility to occur because of altitude.
Why would you train at lower altitudes of 1500-3000m for 2 weeks before performing?
Allows body to adapt to the hypoxic air environment
How long is needed for full acclimatisation?
4-6 weeks
How do people acclimatise to extreme altitudes (4000+m)
Gradual ascent to performance altitude (days at lower levels)
Avoids altitude sickness (can also take drugs to limit altitude sickness)
How long do FIFA recommend to acclimatise at 2700m?
3 days
How long do FIFA recommend to acclimatise at 2750m?
7 days
How long do FIFA recommend to acclimatise at 300m +?
2 weeks
How long does general recommendations state you should acclimatise for at 1000-2000m (low)?
3-5 days
How long does general recommendations state you should acclimatise for at 2000-3000m (moderate)?
2 weeks
How long does general recommendations state you should acclimatise for at 3000m + (high)?
2+ weeks
With regular rest days and no more than 300m a day
How long does general recommendations state you should acclimatise for at 5000m + (extreme)?
4+ weeks
For an aerobic performer, what is the best training option for altitude?
Live high, train low
Live high - gain benefits of high altitude
Train low - higher pO2 so increase intensity and duration of training
What is the optimal altitude training level?
2000-2500m
For 4 weeks
What is the definition of thermoregulation?
The process that allows the body to maintain its core body temperature
What part of the brain regulates temperature?
Hypothalamus
What is the role of the hypothalamus?
Regulate thermoregulatory center to maintain normal core body temperature of 36-37 degrees Celsius. Reflects a balance between heat production and heat loss.
How is heat transferred?
Conduction (1 surface to another)
Convection (via gas/liquid)
Radiation (infrared rays)
Evaporation (liquid/sweat vapour)
At rest how is most heat lost?
Radiation
During exercise, what happens to heat production/loss?
Metabolic heat increases up to 16 times compared to at rest.
Evaporation is most active
What does humidity mean?
Refers to the water content in the air
What happens to heat loss as humidity changes?
Increase humidity, less heat loss by evaporation/sweating.
Less humid, more heat loss by evaporation/sweating
What stimulates the hypothalamus when temperature changes?
Thermoreceptors, peripheral and central, stimulate hypothalamus
What does the hypothalamus stimulate as temperature increases?
Sweat glands to increase sweating
Vasodilation of skin arterioles to help decrease temperature
What counts as a high temperature?
Air temperature that is equal to or more than core body temperature
What is less effective at heat loss when temperatures are high?
Conduction, convection and radiation
What is most effective at losing heat at high temperatures?
Evaporation therefore, increased demand for sweating to regulate temperature. (80% of heat loss)
What is the disadvantage to evaporation being the most effective way to lose heat?
Leads to fluid loss, decreased blood volume, dehydration and therefore, hyperthermia
What facts can be used when talking about how sweating can be negative?
1 litre per hour can be lost in heavy exercise.
1.5-3.5L sweat = 2-4% of body weight per hour.
Elite cyclists lose 6-10% body weight in sweat.
2% loss of body weight is enough to increase core temperature.
What is hyperthermia?
An increase in core body temperature
Apart from water body content, what is lost when sweating?
Electrolytes
What is the effect of sweating when it is hot?
Decrease ability to thermo-regulate.
Allows the core body temperature to rise
What is the cardiovascular drift?
The gradual decrease in stroke volume and increase in heart rate to maintain a constant cardiac output.
Pulmonary/circulatory blood pressure also decrease.
When does the cardiovascular drift happen?
During prolonged aerobic exercise or exercise in the heat in response to
Increased core body temperature due to more heat produced by active muscles and increased heat from the environment.
What happens in the cardiovascular drift?
Higher % Q sent to skin to decrease temp and less blood volume due to sweating.
Causes less VR which decreases EDV which decreases SV.
Q remains constant as HR increases (for 30 mins)
SV/Q eventually decreases due to rising temp and more sweating which increase blood viscosity and decreases blood flow which eventually lowers SV/Q
How does hydration prevent increase in temp?
More water, more resistance to an increase in core body temperature (sweating)
Water maintains blood volume by replacing lost blood plasma to sweat which helps maintain arterial/pulmonary blood pressure
How does heat loss mechanism of the skin compete with active muscles for limited blood volume?
(Cardiovascular response)
Arterioles supplying muscles vasodilate to increase Q which impairs heat transfer to skin so temp increases.
At the same time, thermoregulation causes capillaries / arterioles of the skin to vasodilate to increase Q to skin to decrease temp.
Causes blood pooling at skin surface.
Decreases blood volume (VR/Q) to muscles.
When do heat stress disorders happen?
When there is increase stress on the CV system, at some point the body is unable to compensate for increase demands of exercise and neither the skin or muscles get enough %Q, leading to heat stress disorders.
What is the respiratory systems response to heat?
More dehydration so dry/constricts airways.
Less gaseous exchange.
More respiratory energy demands.
Increase rate/depth of breathing to maintain oxygen uptake.
Diverts Q away from active muscles to respiratory muscles.
Higher risk of EIA of hot and dry environment
What are the 3 overall performance effects of heat?
Heat stress (overloading CV system)
Increase oxygen uptake/cost of aerobic activity
Decrease VO2 max/aerobic capacity/performance.
What are the 3 heat stress disorders that dehydration/hyperthermia leads to?
Heat cramp
Heat exhaustion
Heat stroke
What causes heat cramp?
Dehydration and mineral loss
What is heat exhaustion?
Inability of CV system to meet muscle and skin demands due to increase sweating/dehydration / mineral loss and decrease blood volume
What is heat stroke?
Failure of the thermoregulatory mechanisms and if untreated, is life threatening by leading to a stroke.
How does oxygen uptake effect performance in heat?
Increase oxygen uptake, less efficient aerobic energy system, more anaerobic energy system which increases LA production. More glycogen used so depletes stores.
Leads to lower intensity/duration and earlier fatigue.
How does heat effect aerobic performance?
Increase metabolic rate/heat production/sweating.
2% body weight water loss is enough to increase temperature and impairs performance by 10%.
4-5% decrease performance by 20-30%.
Worst in low intensity/high duration eg 5000m run.
Increase effect the longer duration
Explains why best aerobic performances in cold conditions.
How does heat effect anaerobic performance?
Less effect on explosive/high intensity/low duration anaerobic activity less than 10 secs as more reliant on ATP/PC system eg 100m
What do most endurance athletes need to do before competing in the heat?
Acclimatise
What is heat acclimatisation?
Repeated training for 5-10 days under similar high temperatures of the event.
65-70% of normal work rate in first few days to prevent initial heat stress.
How does the body adapt during heat acclimatisation?
Increase cooling capacity (more efficient at releasing and tolerating heat than non acclimatized athlete)
Decrease exercise temperature which increases heat endurance and decreases fatigue.
How does the body get better at cooling down?
Increase blood flow to skin, more/earlier sweat production in exposed areas which
Reduces skin/body temp with less blood volume to skin which increases blood volume available to active muscles (more SV/Q) which
Decreases HR during exercise
Decrease electrolyte loss in sweat, decreasing muscle cramps.
Decrease rate of muscle glycogen use which increases work rate before fatigue.
What guidelines are there to prevent heat stress?
Schedule races early morning/late evening to avoid extreme solar radiation/high temp.
Cancel race if above 28 degrees or move indoors.
Adequate supply of fluid available at start/during/end.
Cool/ice water immersions to cool a collapsed hyperthermic athlete.
Slow down/stop if symptoms appear.
Start fully hydrated/hyperhydrated
What shouldn’t you do when exercising in heat?
Use rubberized suits to improve weight loss, increase temp/humidity blocks heat loss.
Use sports team uniform/padding as any areas of skin next sweat soaked clothes can equal 100% humidity so decrease evaporation and increase temperature
What happens to the thermoregulatory system as we age?
Decreased ability to adapt to exercise in heat due to a decrease in thermal tolerance and sweating response
What should you do during exercise in heat?
Rehydrate throughout, replaces sweat/water loss.
In longer events top up glucose/electrolytes but still secondary to water. Hypotonic/isotonic drinks.
Reduce initial intensity/pace to counter environmental conditions or decrease intensity/pace if symptoms of heat stress occur.
What should you do after exercise in heat?
Rehydrate - replace sweat/water lost.
Can take 24-48 hours to fully rehydrate.
Drink 1.5X the water lost. Extra 50% speeds up recovery.
Smaller frequent sips of fluid over time is better.
Addition of sodium/salt to replace minerals lost through sweat.
Cooling aids could be used to speed up the time it takes your body to cool down.
Cool/ice water immersions to cool a more severely collapsed hyperthermic athlete and elevated legs to avoid shock.
