Aerobic fitness

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  • Created by: suzy_g138
  • Created on: 10-01-17 10:46

Exercise-related fitness

Exercise-related fitness is the capacity to do work without being exhausted. It is a combination of STRENGTH, FLEXIBILITY & ENDURANCE.

Different types of exercise produce different types of fitness. For example,

Weightlifting increases STRENGTH and (+) ENDURANCE.

While, yoga increases FLEXIBILITY.

Aerobic fitness is person's ability to take up and use sufficient oxygen to do work (physical activity or exercise) for more than 12 mins. of period. It improves respiratory and cardiovascular fitness.

Aerobic fitness requires effective external respiration, oxygen (O2) transport from lungs to cells and O2 uses within the cells.

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Respiratory System

Respiratory System is to get oxygen from the air into body cells to be used in chemical reaction, to release energy and remove carbon dioxide (CO2). The respiration system also involve mechanics of breathing, respiratory volumes and VO2 max.

The function of respiration system is:

To transport air into lungs and,

Help flow of oxygen into the blood stream

Receive waste CO2 from the blood and exhale it.

Respiration is broken into three stages:

  • External respiration
  • O2 transport

  • O2 uptake and use

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Parts of Respiratory System

Upper Respiratory Tract:

  • Mouth, Nose and Nasal cavity
  • Pharynx

  • Larynx

Parts of the Lower Respiratory Tract:

  • Trachea

  • Bronchi

  • Bronchioles

  • Alveoli

  • Diaphragm

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External respiration

External respiration is the exchange of gases in the lung. It involves ventilation (the process of breathing in and out).

O2 is transferred into blood and CO2 is transferred out of the blood. Some of the O2 is absorbed by lungs, while others doesn’t even reach lungs and can only get as far as the nose, trachea or bronchi.  Inside the surface of lungs compromises a large number of tiny sacs known as alveoli. The wall or membrane, of each sap is damp and has good blood supply just below the surface.

Some of the O2 diffuses across the membrane and into the blood, where it is combined with iron-containing protein haemoglobin. While, CO2 in the blood diffuses the other way across the membrane and is breathe out.

Oxygen transport: oxyhaemoglobin (O2 combined with haemoglobin) needs to be transported to all parts of the body. Blood from the lungs enters the heart, which pumps the blood around the body and into body’s cells via arteries.

Oxygen uptake: In body cells, O2 combines with other chemicals from food (glucose) to release energy as well as waste product- CO2 and water. CO2 is then diffuses into blood and is transported via veins back to heart, then to lungs.

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Mechanics of Breathing

When we inhale the intercostal muscles (between the ribs) and diaphragm contract to expand the chest cavity. The diaphragm flattens and moves downwards and the intercostal muscles move the rib cage upwards and out. This increase in size decreases the internal air pressure and so air from the outside (at a now higher pressure that inside the thorax) rushes into the lungs to equalise the pressures.

When we exhale the diaphragm and intercostal muscles relax and return to their resting positions. This reduces the size of the thoracic cavity, thereby increasing the pressure and forcing air out of the lungs.

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Gaseous exchange

Gaseous exchange is the process of O2 and CO2 moving between the lungs and blood. Diffusion occurs when molecules move from an area of high concentration (of that molecule) to an area of low concentration. This occurs during gaseous exchange as the blood in the capillaries surrounding the alveoli has a lower oxygen concentration of O2 than the air in the alveoli which has just been inhaled.

Both alveoli and capillaries have walls which are only one cell thick and allow gases to diffuse across them. The same happens with Carbon Dioxide (CO2). The blood in the surrounding capillaries has a higher concentration of CO2 than the inspired air due to it being a waste product of energy production. Therefore CO2 diffuses the other way, from the capillaries, into the alveoli where it can then be exhaled.

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Respiratory volume

Respiratory volume is the amount of air inhaled, exhaled and stored within lungs given at any time.

  • Tidal volume is the amount of air that moves in and out of the lungs. Tidal volume can vary as the depth of breathing changes. while resting, the normal volume tidal is 500ml or 0.5l.
  • VO2 max is the measure of the peak volume of Oxygen that can be consumed and measured in minute. It is measured in ml/kg/min. VO2 can also be estimated using tests such as a bleep test, or Balke test.

Results vary depending on fitness level, sex, age and genetics. Aerobic fitness can increase the take of oxygen intake. The older you are the lower your VO2 Max is estimated to be. An average score for a twenty-something male would be 40 ml/kg/min with an excellent score being 52 ml/kg/min. An average score for a female of the same age would be 30 ml/kg/min and an excellent score would be 41 ml/kg/min.

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Aerobic and Anaerobic respiration

Aerobic respiration needs oxygen. It is the release of a relatively large amount of energy in cells by the breakdown of food substances in the presence of oxygen. Aerobic respiration equation:

Glucose + oxygen → carbon dioxide + water

Anaerobic respiration does not need oxygen. It is the release of a relatively small amount of energy in cells by the breakdown of food substances in the absence of oxygen. It happens often during hard exercise. Anaerobic Respiration Equation:

Glucose = Ethanol + Carbon Dioxide + Energy

Glucose is not completely broken down, so much less energy is released than during aerobic respiration. There is a build-up of lactic acid in the muscles during vigorous exercise. The lactic acid needs to be oxidised to carbon dioxide and water later.

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Aerobic fitness and external respiration

The level of a person's fitness is influenced by the capacity of the body to carry out all the respiration process:

  • The effectivenss of ventilation depend on the ability to expand lungs and lungs capacity.
  • The ability to expand lung capacity depends partly on the strength of the relevant muscles such as diaphragm and ribcage and the flexibility of the ribcage.
  • Lung capacity depends partly on the size of chest capacity as well as the level of lung tissue disease.
  • The size of chest capacity is influenced by the amount of exercise a person takes.
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Aerobic fitness and Oxygen transport

The effectiveness of oxygen transport depends on the cardiovascular fitness (the ability of the heart, blood cells and lungs to supply oxygen-rich blood to the muscle and the ability of the muscles to use oxygen to produce energy for movement).

  • The heart beats and pumps blood to the lungs and around body. the amount of blood pumped can be calculated: heart rate (bpm) x stroke volume = cardiac output
  • Arteries carry blood away from the heart (always oxygenated apart from the pulmonary artery which goes to the lungs) and have thick muscular walls. It also contains blood under high pressure.

  • Veins carry blood to the heart (always de-oxygenated apart from the pulmonary vein which goes from the lungs to the heart) and have thin walls. It contain blood under low pressure. Veins have valves to prevent blood flowing backwards.

  • Capillaries are found in the muscles and lungs. They are microscopic – one cell thick and gas exchange takes place. Oxygen passes through the capillary wall and into the tissues, carbon dioxide passes from the tissues into the blood. It has a very low blood pressure. In a fit person, there are numerous number of capillaries to take blood into muscles.

  • Red blood cells contain haemoglobin which carries oxygen. Having a low haemoglobin can means it doesn’t transport much oxygen in blood.

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