Exercise Physiology Flashcards
Different conditions will affect performance
Temperature - hot/cold
Humidity - dry/wet
Altitude/Sea Level
How to gain heat in the body
Basal metabolic rate
Hormones
Environment
Muscular Activity
Heat Loss: Conduction
Heat Exchange by two objects in direct contact
- Factors affecting:
- Surface area
- Difference in temperature between surfaces
- Thermal conductivity of material
- Accounts for 3% of heat loss
Heat Loss: Convection
Heat exchange occurred when radiated heat is carried away from the body on air or water currents
Factors affecting:
- Fast air flow = heat loss high, air is continually displaced
- Slow air flow = heat loss low, air is not moved
- Most effective when temperature of air/water around body is low
- Accounts for about 12% of heat loss
Heat loss: Radiation
Occurs when heat is transferred from a warmer body to the cooler surroundings without touching.
Factors affecting:
- When air is cooler than body temperature
- can work in reverse when air temperature exceeds body temperature it acts as a heat gain method
- accounts for 60% heat loss on a cool day
Heat Loss: Evaporation
The cooling of the body as a result of sweating. The amount of heat loss is dependant on the level of activity and environmental conditions
- Increased blood flow to skin is a result of vasodilation
- cooling effect from evaporation of sweat from skin, as a result the cooler blood cools the body
- accounts for 25% heat loss at rest and 80% in hot conditions
Factors affecting:
- age
- gender
- physical fitness
Preferred method of heat loss is dependant on 3 things
Environment:
- outside temperature - if above core temperature, evaporation is only form of heat loss
- Forced convection - if windy convection is used
- Barriers to convection - clothing will minimise effect of convection
- Relative humidity - higher it is, less likely evaporation will work
Age:
- Children sweat less than adults as their sweat glands are not properly developed
Physiological state:
- Rate of heat production
- Hydration state - reduction in blood plasma (water) results in decreased sweat rate
Dehydration:
- occurs when the amount of water leaving the body exceeds the amount that you are taking in
- We lose water by:
- sweating
- breathing
- urinating
- Can cause dizziness, headache, fatigue, nausea
- Heat exhaustion - dehydration as well as an ineffective circulatory system
- Heat stroke - severe dehydration
Rest and Exercise in heat
- at rest, the bodies heart rate and cardiac output increase
- when exercising the body experiences double heat load:
- Producing heat from muscular activity
- environmental temperatures above core temperature
- double heat load creates competition for blood flow
- muscles and vital organs require blood flow to sustain energy and metabolic action
- skin requires blood to remove heat from the body
Cardiac Drift:
- after prolonged exercise in mild to high heat
- cooling mechanism stops with less blood being sent to the skin but rather to the muscles means the body overheats faster
- less blood available to pump because of dehydration
- stroke volume decreases as heart rate increases (more pumps with less blood being transported around the body)
Methods to cope with exercising in heat:
Hyper-hydrate:
- Consume 300-400ml just before performance and 600ml 3-4 hours before exercise
- avoid diuretics as they promote urination eg. Caffeine
Consume 150-200ml every 15mins during performance
Wear loose fitting, light coloured clothing
- this promotes heat loss via convection and evaporation
Pre-cool core body temperature
- Ice vests, immersion in cold water, slushies
Acclimatise
Post exercise consume 1.5x amount lost in fluids
- This accounts for urination
- consume slightly salty fluids to keep osmolality high, preventing urination
Affects of training in heat
The ability to adapt to a different environment like a new temperature or altitude
Athletes who compete in heat can expect effects of:
- having to work harder to achieve the same intensity as in cooler climates
- rapid dehydration and a faster rate of fatigue
- an elevated heart rate when exercising at the same intensity as in cooler climates
- a higher resting body temperature
- impaired performance compared to in cooler conditions
Precautions taken to work in heat and humidity
- ensure sufficient electrolyte replacement is managed after training
- monitor fluid intake with fluid replacement during training and competition
- avoid coffee and alcohol
- monitor body weight and urine volume
- undertake glycerol loading to enhance fluid uptake
- take measures to reduce core temperature through ice vests, cool drinks, staying in the shade, wearing appropriate clothing and using evaporative fans
Adaptations to heat acclimatisation
- increased plasma volume (reduces tendency for an elevated heart rate)
- reduced core temperature at the onset of sweating
- increased sweat rate
- more dilute sweat which keeps salt in the body
- exercise with a lower core and skin temperature
- heart rate is lower with a more effective cooling system
- more blood sent to muscles during performance, rather than skin for heat loss
Hyperthermia
Overheating and it occurs when the body experiences extreme loss of salt and water through sweating
Protection against Cold temperatures
- Wearing suitable clothing that still allows for evaporation to occur
Performance in the cold and resultant shivering
- Increased sub maximal VO2 at different exercise intensities
- Fine motor skills deteriorate due to vasoconstriction (constriction of blood vessels increasing pressure)
- Shivering is involuntary muscle contractions in response to chilling effect of cool temperature
- shivering reduces coordination
Risk of Dehydration in the Cold
- Inhaled air is very cold and dry - requiring more warmth produced by the body to warm it, therefore needing lots of water in this process
Hypothermia
Hypothermia is when the victims inner body temperature decreases to a level less then 35 degrees
May occur via: prolonged exposure to cold, windy weather and cold water
Symptoms:
- uncontrollable shivering
- loss of coordination
- shallow breathing and a slow pulse
- memory loss and slurred speech
- unconsciousness (if core temperature drops below 32 degrees)
Cold Acclimatisation
- Should be done 7-10 days prior to competition
- No evidence to suggest that there are any physiological benefits to training in a cold environment