Oxygen Uptake and Performance

PSE 4U1

Exercise Science

Unit 6

Energy and Performance

• Major function of the cardiovascular system during exercise is to deliver oxygen to working muscles

• Cardiovascular endurance depends on how efficiently the Cardiorespiratory system works, that is, the ability of the lungs, heart and blood vessels to take oxygen and process it and deliver it to working muscles

Performance depends on:

1. Availability of oxygen in the air (approx. 20%)2. Diffusion of oxygen from lungs into blood3. Chemical binding of oxygen with hemoglobin

(CO has 200-250 times greater affinity to heme than does O2)

4. Ability of cells to pick up oxygen from the blood in exchange for carbon dioxide and other waste products

5. Ability to eliminate carbon dioxide through the lungs and start over

Maximal Oxygen Consumption

• The rate at which oxygen is delivered and used by the body

• Abbrev. VO2max or MVO2

• Best indicator of cardiovascular (aerobic) fitness expressed relative to body weight, measured as ml/kg/min

• The higher the value, the higher the oxygen available for each unit of body weight; therefore, more work can be performed

MVO2 / VO2max depends on

1. Ventilation: the volume of air that can be taken into the lungs/min

2. Pulmonary Diffusion: oxygen and carbon dioxide exchange in and out of blood (capillaries)

3. Transportation of Gases: the ability of blood to carry oxygen (hemoglobin)

4. Cardiac Output: amount of blood that can be circulated per minute (SV x HR)

5. Ability of muscles to use delivered oxygen (anaerobic threshold-mitochondria)

Indices of Cardiorespiratory Fitness

• Maximum oxygen uptake (MVO2 / VO2max)

• Resting HR• HR during fixed submaximal exercise/load• Endurance performance• Recovery HR

Correlation between HR and O2 uptake

• As HR increases so too does O2 uptake

Anaerobic Threshold

• Onset of blood lactate accumulation

• Percent of VO2 maximum at which one can exercise without producing lactic acid

• Anaerobic threshold is approximately 50% of VO2max in an untrained individual and 65% in a trained individual

• 10-15% increase in VO2max with training compared to an 80-90% increase in anaerobic threshold

Lactate ThresholdLactate Threshold

Testing for Anaerobic Threshold

1. Talk Test: • Difficult to talk because CO2 is held in

• Decrease in O2 uptake; therefore, lactic acid increases

• Breathing in interrupts speech; therefore, the talk test is effective

2. Heart Rate:• Percent of max HR will help determine anaerobic

threshold

Testing for Anaerobic Threshold

3. Breath Sound Check• O2 binds with hydrogen ion to form H2O

• Hydrogen ions produced by lactic acid increases ventilation thereby increasing oxygen uptake

• Hearing your breath during exercise allows you to train at your ventilatory threshold

Training Adaptations1. Increase in the amount of hemoglobin2. Increase in maximal cardiac output as heart

becomes stronger3. Capillarization

• Increase in size and number of capillaries around muscle fibres, therefore, increasing blood flow and O2 uptake

4. Increased efficiency in gas exchange5. Increase ability of muscle to use oxygen6. Increase in Mitochondria

– ATP production increases; therefore, you can train longer and harder aerobically (Krebs, Beta Oxi, ETC)

– Can increase about 120% after 24 months

7. Increase a-vO2 difference

8. Conversion of FT(b) to FT(a)– Fast twitch muscle fibres become more aerobic

9. VO2max increase in 10-15%

– Increase in anaerobic threshold

10. Fibre size (muscle)– Increase; therefore, more actin and myosin

available for contraction

a-vO2 Differencea-vO2 Difference

Arteriovenous oxygen difference, or a-vO2 diff, is the difference in the oxygen content of the blood between the arterial blood and the venous blood. It’s a good way to see how much O2 is delivered and used by muscle

Physiological Adaptations Due to Physiological Adaptations Due to Endurance TrainingEndurance Training

Factors affecting MVO2 / VO2max

• Diet

• Exercise

• Lifestyle