STAGE 3 PHYSICAL EDUCATION
Need To know – Exercise physiology
1. Environmental Conditions and Performance
* Environmental Condition – HEAT
1. Methods of Heat Transfer
Conduction - Heat exchanged by 2 objects in contact.
Convection - Heat exchange by contact with a fluid that is flowing which will occur when heat is carried away from body by air or water currents. Accounts for 12% of heat loss. Radiation - 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.
2. Double Heat load – when does it occur and what impact does it have on the body / performance? A double heat load occurs when exercising in the heat. A high rate of sweating results in a significant loss of body fluid and consequently blood plasma volume. The reduced blood plasma volume inhibits the ability to continue to deliver blood to both the working muscles and the periphery for cooling via sweat evaporation. In addition, there is a decreased stroke volume, leading to an increased heart rate to compensate. With significantly reduced plasma volume, the body will priorities blood supply to the working muscles, rather than the periphery. This means less blood flow to the skin, limiting further cooling by evaporation and ultimately inhibiting continued performance.
3. Effect of heat on aerobic/anaerobic exercise.
1. At rest in the heat, Heart rate and stroke volume increase, to allow the body to send more blood to the skin, creating a cooling effect via evaporation. 2. At the commencement of exercise, heart rate and stroke volume continue to increase as the body must also send blood to the working muscles. 3. Whilst exercising, core body temperatures starts to increase which places extra strain on the body’s cooling mechanism - the hotter it is the more dependent the body becomes on evaporation. 4. A hot ambient and core temperature creates a double-heat load. 5. Players should drink fluid to remain hydrated.
6. As exercise continues, players continue to drink, however fluid loss exceeds fluid intake (dehydration) resulting in dehydration occurring. 7. Dehydration results in a loss of plasma volume which affects the amount of blood which can be delivered around the body. 8. As blood volume drops, the body must try and maintain cardiac output to ensure enough blood is still sent to the working muscles and skin. 9. This leads to a reduced performance and an increase in core body temperature which may result in a headache, dizziness or nausea. Further sweat loss occurs leading to severe dehydration. 10. Further sweat loss occurs leading to severe dehydration. 11. With reduced cardiac output, the body must now make a critical decision, as to wether to send blood to the working muscles and vital organs? or to the skin for cooling? 12. The body chooses muscles and vital organs leading to reduced heat loss via evaporation. As a result core temperature rises placing the athlete at extreme risk of unconsciousness, coma, death if exercise continues.
4. Dehydration – signs / symptoms / dangers / prevention.
Dehydration occurs when the amount of water leaving the body is greater than the amount being taken in.
5. Cardiac drift – when / why / impact on body / performance. * In an attempt to maintain cardiac output, Heart rate increases. * This increase in heart rate is relatively smaller than the decrease in Stroke volume, therefore cardiac output is reduced. * As a result, skin blood flow decreases and oxygen sent to working muscles is also reduced, placing extra strain on the body to maintain exercise levels. * A reduction in blood flow to the working muscles increase the production of lactic acid * A reduction in blood flow to the skin reduces the rate of sweating, inhibiting the body’s ability to lose heat via evaporation. These...