exercise phys Flashcards
what is vasodilation?
increase size
what is vasoconstriction?
decrease size
4 ways of gaining heat?
hormones
environment
muscular activity
metabolic rate
4 ways of losing heat?
- Conduction
- Convection
- Radiation
- Evaporation
what is double heat load?
Heat is produced within the muscles when they are working, and also is present in the environment
conduction?
is the heat exchanged by two objects that are in contact with each other.
convection?
is heat exchange by contact between an object and fluid that is flowing. This occurs when heat is carried away from the body by air or water currents.
radiation?
occurs when heat is transferred from a warmer body to the cooler surroundings without physical contact.
evaporation?
is the cooling of the body as a result of the vaporisation of sweat.
what effects the rate of sweat?
Gender (males sweat more than females)
The number of sweat glands
Body surface area (Increased SA increased sweating)
How fit they are (Increased fitness increased sweating
factors affecting conduction?
Difference in temperature between the two objects (heat flows from hot to cold)
Surface area (Increased surface area increased heat loss)
Thermal conductivity of material (e.g. metal is a good conductor of heat)
factors affecting convention?
The speed and temperature of the air/water. E.g. if a breeze gets stronger, the heat loss occurs faster.
The layer of warm air that continually surrounds our body is displaced by cold air when air temperature is lower than skin temperature
heat loss by exposing more of their body surface area to the cooler surrounds
factors affecting radiation?
Radiation accounts for 60% of heat loss from body at rest on a cool day.
- Heat loss occurs when a person’s core temperature is higher than the ambient temperature.
- Heat gain occurs when a person’s core temperature is lower than the ambient temperature.
explaining evaporation? (4)
- At rest, evaporation accounts for 25% of heat loss. When active, this can increase up to 80%.
- When the body exercises, muscles create heat.
To avoid overheating, the body uses blood to help regulate temperature. - Heat is transferred to the skin’s surface via the blood (vasodilation of vessels), where it is released as sweat.
Evaporation of the sweat on the skin creates a cooling effect. - The cooled skin then cools the blood at the surface, maintaining the body’s core temperature.
- better in dry heat conditions (over humidity)
excessive sweating
Excessive sweating leads to a loss of body fluids, and when level of body fluid drops, the body’s core temperature increases.
It is this gradual dehydration that leads to heat exhaustion and heatstroke.
Sweat loss can reach 6 – 10% of body mass
> 2% generally means performance and thermoregulation are compromised
3 ways of heat transfer
- environment
- ambient temp
- convention
- radiating surfaces
- relative humidity
- age
- childern dont sweat as much
- physiological state
- how much work is performed
- hydration state
dehydration
occurs when the amount of water leaving the body is greater than the amount of water being taken in.
cardiac drfit (explanation)
creates a competition for blood flow.
- The muscles and vital organs require blood flow to sustain energy metabolism
- The skin requires blood flow so it can release heat to regulate body temperature
- The blood flowing to the skin cannot help to transport oxygen to the working muscles, which can impact performance
hyper-hydration
Involves increasing the body’s fluid stores by consuming extra fluid prior to an event
pre exercise how much water
1L prior to exercise is recommended
600ml 3 – 4 hours before game/competition
400ml just prior to game to prime the stomach
Avoid caffeine – it is a diuretic & increases fluid loss
Allows the athlete to sweat more before performance is inhibited
water during exercise
Drink ~200ml of water every 15 minutes during activity. This is influenced by environmental conditions and exercise intensity.
water post exercise
Want to replenish back to pre-exercise weight
For every litre of sweat loss, consume
1.5L as you will lose some of this through urine
Consume slightly salty fluid to keep osmolality higher so you don’t urinate as much.
hyponatremia
is an abnormally low concentration of sodium (salt/electrolytes) in the blood
what is heat acclimatization
is when heat tolerance is improved by repeated exposure to hot environments.
how to acclimatise to heat
How long?- The first sessions should be ~15-20 mins, and be light to moderate activity
This should increase to 45 – 60 mins daily for ~ 8 – 9 days with an increase in exercise intensity & duration.
5 – 10 days living and training in heat is recommended.
Where?Athletes who are unable to use natural acclimatisation should use climate chambers, saunas or sweat clothing.
When?Should be completed 4 – 6 weeks prior to competition and then 2 sessions per week leading up to competition to maintain the benefits
major adaptations to heat
sweating earlier
cardiovascular
what happens to sweating when heat acclimatized
Increase blood plasma volume (more fluid stored in the blood), increases the length of time to dehydration
Increases sweat rate
Start sweating at lower core temperature
Sweat becomes more dilute and is distributed over the body more effectively
what happen to the cardiovascular system when heat acclimatized
They have a lower HR than an unacclimatised athlete
The lower core temperature also reduces the body’s need to send blood to the skin for cooling, resulting in a greater % of Q going to the active muscles.
methods to cope with exercising in the heat
hydration
clothing
pre cool body temp
modify training
Clothing to where in the heat
Wear loose fitting, light coloured clothing to permit free circulation of air between the skin and the environment, promoting convection and evaporation from the skin.
how can you pre cool body
Pre cool core body temperature via a range of methods including ice towels/vests, immersion in cold water, drinking iced water/slushies
modify training for training in the heat
Frequent rest breaks. Avoid training during the heat of the day i.e. morning sessions
or early evening Reduce training volume/intensity/duration
altitude
True altitude is the actual elevation above mean sea level.
how altitude effects performance
The alveoli are low in O2 & low in CO2
The venous blood is also low in O2 & high in CO2
Therefore there is only a small pressure differential, making it difficult for diffusion of oxygen from the alveoli into the capillaries
altitude acclimatization
Altitude acclimatisation describes the improved physiological response to altitude hypoxia. Hypoxia is a deficiency in the amount of oxygen reaching the tissues.
3 methods to altitude acclimatization
Living high and training low
Living and training high
Living low and training high
living high and training low
Involves daily intermittent exposure to artificial altitude environments whilst maintaining normal training intensities.
This is more beneficial because athletes can still maintain their training intensity whilst getting added benefits of altitude exposure & the associated physiological adaptations.
living high and training high
The athlete lives at high altitude to achieve the physiological benefits of decreased oxygen concentration and trains at altitude to obtain adaptations.
This usually requires the athlete to go to at least 2000 – 3000m above sea level, and live and train for about 3 – 4 weeks.
altitude sickness is as well
This method is best suited to preparing teams to compete at altitude, not to compete at sea level.
living low and training high
Athletes live at sea level but train in hypobaric chambers or altitude tents to simulate a hypoxic environment.
There is no evidence that this method is effective in gaining the chronic adaptations achieved by using the ”live high, train low” method.
acute adaptations to increasing altitude
increased respiratory rate
increased tidal volume
increased nausea, head ache
increased HR and Cardiac output during rest
decreased plasma volume