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Maximal Oxygen Consumption

Maximal Oxygen Consumption. Direct Measurement. Maximal Oxygen Consumption. VO 2 max Greatest volume of oxygen that the body can consume per unit time Regarded as “gold standard” of aerobic fitness. Difference Between VO 2 max and VO 2 peak.

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Maximal Oxygen Consumption

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  1. Maximal Oxygen Consumption Direct Measurement

  2. Maximal Oxygen Consumption • VO2max • Greatest volume of oxygen that the body can consume per unit time • Regarded as “gold standard” of aerobic fitness

  3. Difference Between VO2max and VO2peak • VO2peak is the highest level of oxygen consumption that can be achieved during a mode of exercise • VO2max is the largest VO2peak for an individual • The mode of exercise during which VO2max occurs can vary, but is typically running or stair stepping • For individuals trained at a specific mode of exercise, it usually matches the mode of the training

  4. VO2peak = Delivery x Utilization • Influenced by amount of O2 supplied to muscles and ability of muscles to utilize available O2 • VO2 = Q x (a-vO2diff.) • Called The Fick Equation • Q = Cardiac Output (L Blood/min) • a-vO2 diff. = difference between arterial and venous oxygen content (L O2/L Blood)

  5. Factors Involved In Delivery and Utilization • Delivery • cardiac output 1. blood volume 2. venous return 3. resistance to blood flow • muscle capillary density • Utilization • amount of lean mass • #/size of mitochondria • #/activity of oxidative enzymes • muscle fiber type

  6. Influences on VO2max • Largely genetically determined • Training can improve it 5-20%, depending on initial fitness level • Males score ~ 15–30% higher than females • Differences between gender due to: • Muscle mass • Hemoglobin concentration • However, many women can score higher than average men

  7. VO2peak – Direct Measurement • Can be measured either in absolute terms (liters per minute, L/min) or in relative terms (milliliters per kilogram of body weight per minute, ml/kg/min) • Direct measurement during a maximum, graded exercise test provides most accurate assessment • Increases in workload by increasing speed/grade of treadmill or resistance on bike until subject cannot continue

  8. Measurement Issues • Involves a large supramaximal anaerobic component • How do we know when the VO2max has been reached

  9. Three Criteria for a Valid Peak Test • RER > 1.1 • 2) > 90% age-predicted max HR • 3) Plateau in VO2 w/ increased intensity (not all subjects exhibit a plateau) • Change < 0.15 L O2/min (absolute VO2)

  10. Why RER? • As exercise intensity increases, RER increases due to the greater increase in VCO2 relative to VO2 a. changes in substrate utilized b. non-metabolic CO2 (the product of anaerobic metabolism) • RER allows us to see when the anaerobic contribution begins

  11. Age (years) Very High High Good Average Fair Low Males 20-29 >61 53-61 43-52 34-42 25-33 <25 30-39 >57 49-57 39-48 31-38 23-30 <23 40-49 >53 45-53 36-44 27-35 20-26 <20 50-59 >49 43-49 34-42 25-33 18-24 <18 60-69 >45 41-45 31-40 23-30 16-22 <16 Females 20-29 >57 49-57 38-48 31-37 24-30 <24 30-39 >53 45-53 34-44 28-33 20-27 <20 40-49 >50 42-50 31-41 24-30 17-23 <17 50-59 >42 38-42 28-37 21-27 15-20 <15 60-69 >39 35-39 24-34 18-23 13-17 <13 Norm Values for VO2max (ml/kg/min)

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