Maximal Oxygen Consumption
Direct Measurement
Maximal Oxygen Consumption
• VO2max
• Greatest volume of oxygen that the body
can consume per unit time
• Regarded as “gold standard” of aerobic
fitness
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
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)
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
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
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
Measurement Issues
• Involves a large supramaximal anaerobic
component
• How do we know when the VO2max has
been reached
Three Criteria for a Valid Peak Test
1) 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)
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
Norm Values for VO2max (ml/kg/min)
Age
(years)
Males
Very High
High
Good
Average
Fair
Low
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
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
Females