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: Availability of oxygen in the air (approx. 20%) Diffusion of oxygen from lungs into blood Chemical binding of oxygen with hemoglobin (CO has 200-250 times greater affinity to heme than does O2) Ability of cells to pick up oxygen from the blood in exchange for carbon dioxide and other waste products 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 Ventilation: the volume of air that can be taken into the lungs/min Pulmonary Diffusion: oxygen and carbon dioxide exchange in and out of blood (capillaries) Transportation of Gases: the ability of blood to carry oxygen (hemoglobin) Cardiac Output: amount of blood that can be circulated per minute (SV x HR) 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 Threshold

Testing for Anaerobic Threshold 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 Heart Rate: Percent of max HR will help determine anaerobic threshold

Testing for Anaerobic Threshold 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 Adaptations Increase in the amount of hemoglobin Increase in maximal cardiac output as heart becomes stronger Capillarization Increase in size and number of capillaries around muscle fibres, therefore, increasing blood flow and O2 uptake Increased efficiency in gas exchange Increase ability of muscle to use oxygen 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 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 Endurance Training

Factors affecting MVO2 / VO2max Diet Exercise Lifestyle