Environmental effects on body systems

Question 1

What happens as altitude increases?

Answer 1

1. Barometric pressure (pressure exerted by Earth’s atmosphere) decreases
2. Partial pressure of oxygen decreases, which severely impacts performance
3. Negative impact on the diffusion gradient is greater, so oxygen will move from one area to another slower.

Question 2

What is the partial pressure of oxygen at different diffusion gradients and altitudes?

Answer 2

1. Sea level, pO2=159mmHg, has a diffusion gradient of 119 to capillary blood
2. 3600m above sea level, pO2 is 105mmHg, has a diffusion gradient of 65 to capillary blood
3. 8800m above sea level, pO2 is 43mmHg, has a diffusion gradient of 3 to capillary blood.

Question 3

What are the consequences of competing at high altitude?

Answer 3

1. Plasma volume decreases by 25% to allow increase in density of RBCs
2. Stroke volume decreases, which increases HR
3. Maximal cardiac output, stroke volume and HR decrease during maximal-intensity exercise
4. Increased breathing frequency

Question 4

What is the process of acclimatisation?

Answer 4

1. Altitude starts to have an effect around 1500m, although different people acclimatise at different speeds, guidelines allow:
2. 3-5 days for low-altitude performance (1000-2000m)
3. 1-2 weeks for moderate-altitude performance (2000-3000m)
4. 2+ weeks for high altitude (3000+), athletes going above 3000m should sleep no more than 300m higher each day and have regular rest days to prevent altitude sickness
5. 4+ weeks for extreme altitude (5000-5500m), e.g. a climber will spend one month at base camp before making a summit attempt at Everest.

Question 5

What are the benefits of acclimatisation on the cardiovascular and respiratory systems?

Answer 5

1. Increased RBC production, due to increased EPO
2. SV and CO reduce as O2 extraction becomes more efficient
3. Breathing rate and ventilation stabilise, although remain elevated at rest, compared to sea levels
4. Reduced incidences of altitude sickness, headaches, breathlessness, poor sleep and lack of appetite.

Question 6

!!! How does the body regulate heat during exercise?

Answer 6

1. Thermoregulation is the process of maintaining internal core temperature
2. Thermoreceptors deep in the core sense a change in temperature
3. If core temperature rises, metabolic heat is transported by the circulation blood to the durance of the body and released mostly by convection and evaporation.

Question 7

!!! What are the consequences of an athlete exercising in heat?

Answer 7

1. An athlete exercising in the heat can lose around 2-3 litres of sweat per hour, which if not replaced decreases blood volume and dehydration
2. The rate of heat loss through sweating is affected by humidity.

Question 8

!!! What is hyperthermia, what is it caused by?

Answer 8

1. Hyperthermia is the significantly raised core body temperature, caused by:
   - High and prolonged exercise intensities
   - High air temperatures
   - High humidity.

Question 9

!!! What are thermoreceptors?

Answer 9

Thermoreceptors are sensory receptors which sense a change in temp and relay info to the brain.

Question 10

!!! What is humidity?

Answer 10

Humidity is the amount of water vapour in the atmospheric air.

Question 11

!!! What is cardiovascular drift?

Answer 11

Cardiovascular drift is caused by prolonged exercise in the heat which rises core body temperature.

Question 12

!!! What are the effects and implications of heat and humidity on the cardiovascular system?

Answer 12

1. Dilation of arterioles and capillaries to the skin
   - Which increases blood flow and pooling in the limbs
2. Decreased blood volume, VR, SV, CO and BP
   - Which increases HR to compensate
   - Increases strain on the cardiovascular system
   - Reduced O2 transport to the working muscles

Question 13

!!! What are the effects and implications of heat and humidity on the respiratory system?

Answer 13

1. Dehydration and drying of the airways in temperatures above 32 degrees makes breathing difficult
   - Which increases mucus production
   - Constricts the airways
   - Decreases volume of air for gaseous exchange
2. Increased breathing frequency to maintain oxygen consumption
   - Which increases oxygen ‘cost’ of exercise
3. High levels of sunlight increase the effects of pollutants in the air
   - Which increases irritation of airways, leading to coughing, wheezing or asthma symptoms.

Question 14

!!! What are the strategies to maximise performance in heat and humidity, pre during and post exercise?

Answer 14

Pre competition:

1. 7-14 days of acclimatisation in the same conditions to increase the body’s tolerance to heat
2. Using cooling aids such as ice vests to reduce core temperature and delay effects of dehydration

During competition:

1. Pacing strategies to reduce the feelings of exertion at low-exercise intensities
2. Wearing suitable clothing to maximise heat loss
3. Rehydrating as often and as much as possible with hypotonic or isotonic solution

Post competition:

1. Using cooling aids such as fans
2. Rehydrating using isotonic solution to replace lost fluids, glucose and electrolytes.