Exercise Physiology

Energetics
1. The study of the energy demands of work
Ergometry
1. Assesses individual performance, as well as associated physiological changes
Performance Capacity
1. Ability to respond to a physical load
  1. e.g. how quickly someone can run a mile
2. Limited by the rate at which the body can convert chemical energy in food to mechanical energy of the muscles.
  1. This efficiency is affected by size, gender, fitness level and skill
3. Good efficiency
  1. Effectiveness of muscles and other systems
    1. Cardiovascular system has to efficiently transport oxygen, CO2 and glucose around the body
    2. Respiratory system must acquire O2 and eliminate CO2 effectively
  2. Efficiency refers to the energy expenditure in relation to the work accomplished
    1. Efficiency = work done / energy consumed
  3. Rarely exceeds 25%
    1. Most energy is lost at heat
      1. Makes the process inefficient
Considers the effects of hard physical labour on the human body
1. Key to maximising performance is the ability to inspire and transport oxygen, and to utilise both oxygen and food substrates efficiently
Measuring
1. Work done
  1. Directly obtained from calibrated exercise apparatus
2. Converted energy
  1. Indirectly obtained
    1. Calorimeter impractical for humans
  2. Oxygen consumption
    1. Oxygen is consumed in all biological oxidation reactions and so it reflects the energy generated
    2. Air collected in Douglas bag or measured directly by continuous monitoring
      1. Expired air is sampled for O2 and CO2 concentration and the total volume of expired air is recorded
  3. Energy consumed
    1. Respiratory quotient (RQ) of the food substrate is a measure of the energy generating potential of the food
      1. Calculated from the ratio of CO2 produced over O2 consumed
        e.g. less CO2 is given off compared to O2 consumed in fat, so the RQ is 0.7
        Respiratory Exchange Ratio (RER) is calculated in the same way as RQ, but reflects the production of CO2
    2. Determined from O2 taken up and the RQ
      1. Converted energy = O2 consumed x RQ
Muscles
1. Short term stores of ATP and creatine phosphate
  1. Used over short periods of work
  2. ATP stores only available for contractile processes for a few seconds
  3. CP donates a phosphate group to ADP to make ATP
    1. Reserves used up in the first minute
  4. Feeling of tiredness comes from the utilisation of stores in muscle cells and the start of anaerobic respiration
    1. Forms lactic acid
    2. Aerobic respiration does not contribute until a few minutes prior to the start of work
2. Glycolysis
  1. Produces 2 ATP for 1 glucose molecule
  2. Quicker than aerobic respiration
    1. Less efficient, uses up glucose quickly
  3. Creates pyruvic acid
    1. Converted to lactic acid
3. Oxidative phosphorylation
  1. 36 ATP per glucose molecule
    1. 28 net ATP
4. Exercise is initially anaerobic as stores are used up. RER increases due to CO2 concentration. Anaerobic continues until a steady state is established. Aerobic respiration will then start and RER will stabilise. Subjects must be in a steady aerobic state in order to measure muscle efficiency
Fatigue
1. Fall in pH due to lactic acid build up
2. Ratio of fast and slow twitch fibres
  1. Vary, but cannot be changed
3. Endurance training allows muscles to use oxygen more efficiently
  1. Mitachondria numbers increase - energy stores rise
  2. Number of capillaries increase and blood vessels enlarge
    1. Increases blood flow and reduces blood pressure
  3. Reverts entirely after 6 months if muscles are not used
  4. Stroke volume can increase where heart rate cannot improve
    1. This allows more blood to flow per heart beat
    2. HR has an individual maximum, governed by fatigue
    3. Lower resting HR
    4. Relative increase in HR in an athlete is greater than in a sedentary person
      1. Same amount of O2 is consumed at a lower HR
Breathing
1. Increases during exercise
2. pH based reflex response
  1. CO2 dissolved in the blood produces carbonic acid
    1. Acidity increase detected by peripheral receptors. Sent to respiratory centre in the medulla
      1. Breathing rate increases. Take in more O2, expire more CO2
3. VO2 max is the maximum oxygen consumption and it is a measurable indicator of fitness
4. Training increases strength of ventilator muscles and tidal volume - amount of air per breath

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Exercise Physiology

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	Created by Lydia Buckmaster over 10 years ago