Exercise in Heat Flashcards
3 main causes of hyperthermia
- High and prolonged exercise intensities
- High air temperatures
- High relative humidity
For the performer the redirection of blood flow to the skin to aid cooling: (4 things)
- limits blood flow to the muscles
- limits venous return
Because
- rising core temperature alters the function of protein molecules
- affects the rate of chemical reactions
Effect of heat, humidity & thermoregulatory response on cardiovascular system and their implications (5 things)
Dilation of arterioles and capillaries leading to the skin
- Increased blood flow
- Increased blood pooling in the limbs
Decreased blood volume, venous return, stroke volume, cardiac output and blood pressure
- Increased HR to compensate
- Increased strain on the CV system
- Reduced O2 transport to the working muscles
Overall effects of heat, humidity & thermoregulatory response (4 things)
- Increased oxygen ‘cost’ of activity
- Decreased aerobic energy production = This means the more emphasis is placed on the anaerobic energy production, and use of carbohydrates store more quickly
- Exercise duration decreases as lactic acid accumulation; resulting in early fatigue
- Strength endurance and aerobic capacity are reduced
Performance decreases in mid-long distance
Effect on performance – e.g. marathon runner (3 things)
- Marathon runners who finish in 180 minutes may see a decrease in performance from 3% at 10℃ up to 12% at 25℃
- This would increase their finishing time to 184.5 minutes and 201.6 minutes respectively.
- At higher temperatures, perceived exertion will feel harder for the athlete and performance times will be severely affected
Pre competition Acclimatisation - acclimatisation in the same conditions to increase the body’s tolerance to heat by: (3 things)
- Increasing plasma volume, the onset and rate of sweating, and the efficiency of cardiac output distribution
- Decreasing the loss of electrolytes within the sweat, which limits fatigue and cramping
- Decreasing heart rate at a given pace and temperature
Precompetition coolings aids?
Use cooling aids such as ice vests to reduce core temperature and delay effects of dehydration
How long should be given to allow acclimatisation to heat to occur pre-competition?
7-14 days
During competition strategies for exercising in heat (3 things)
- Use pacing strategies to reduce feeling of exertion at low intensity activities
- Wear suitable clothing that maximises heat loss, removing sweat from the skin rapidly, such as lightweight compression wear
- Rehydrate as often as possible with hypotonic and isotonic solutions
Post competition strategies for exercising in heat (2 things)
- Cooling aids such as towels and cold fans, aid the return of core body temperature gradually
- Rehydrate using isotonic solutions that replace lost fluids, glucose and electrolytes
Explain what is meant by the term ‘cardiovascular drift’. 4 marks
Four marks from:
- cardiovascular drift is the (potential)side effects of exercise in a hot climate
- cardiovascular drift leads to an increased heart rate at given intensity of (sub maximal exercise)
- reduced plasma volume / (due to)water loss during exercise(which means) reduced stroke volume
- to maintain cardiac output HR has to increase
Effect on respiratory system
Dehydration and drying of the airways in temperatures above 32℃ makes breathing difficult
- Increased mucus production
- Constriction of the airways
- Decreased volume of air for gaseous exchange
Increased breathing frequency to maintain O2 consumption
- Increased ‘cost’ of exercise
High levels of sunlight increase the effects of pollutants in the air
- Increased irritation of airways; leading to coughing, wheezing or asthma symptoms
