Dr. Robert Robergs
Fall, 2010
VO2max Measurement and Analysis
Dr. Robert A. Robergs, Ph.D., EPC, FASEP
Director:
Exercise Physiology Laboratories
Exercise Science Program
The University of New Mexico
Albuquerque, NM 87131-1258
www.unm.edu/~rrobergs
Early History
“In running the oxygen requirement
increases continuously as the speed
increases, ….; the actual oxygen intake,
however, reaches a maximum beyond
which no effort can drive it. The oxygen
intake may attain its maximum and remain
constant merely because it cannot go any
higher owing to the limitations of the
circulatory and respiratory system.”
Archibald Vivian Hill
(Hill A.V. and H. Lupton. QQ J Med 1923; 16:135-171.)
In performing his research, Hill used,
• 6-7 subjects
• limited running speeds • discontinuous running protocols
• combined data from multiple subjects
VO2max Issues
1
Dr. Robert Robergs
Fall, 2010
What is VO2max
VO2
VO2max
Cardiorespiratory
limitations
Duration should be ~8-10 min
Time or Intensity
Definitions:
• The
maximum rate oxygen can be taken in
(pulmonary), transported (circulatory), and
utilized (peripheral) for energy production.
• The maximal rate at which the body can
consume oxygen during exercise.
Other “less correct” terms!
“aerobic capacity”
“aerobic power”
“maximal cardiorespiratory capacity”
VO2max Issues
2
Dr. Robert Robergs
Fall, 2010
Powers and Howley, 1997, p: 50
“VO2max represents the physiological ceiling for the ability of
the oxygen transport system to deliver O2 to contracting
muscles.”
Wilmore and Costill, 1994, p: 11
“…. Oxygen consumption peaks and remains constant or drops
slightly, even though work intensity continues to increase….
The best single measurement of cardiorespiratory endurance
and aerobic fitness.”
VO2max Issues
3
Dr. Robert Robergs
Fall, 2010
Robergs and Roberts, 1998, p: 227
“… the maximal rate that the body can consume oxygen during
exercise… detected as a plateau despite further increases in
exercise intensity...”
VO2max Issues
4
Dr. Robert Robergs
Fall, 2010
Determinants of VO2max
CENTRAL
HR x SV
Cardiac Output
PERIPHERAL
 A-aPO2
SaO2 [Hb]
oxygen delivery
PO2 gradients
VO2max = Qmax x a-vO2max
capillary density
muscle mass fiber dimensions
O2 supply demand relationships
Peripheral Oxygen Diffusion
VO2max Issues
5
Dr. Robert Robergs
Fall, 2010
Plateau???
2800
2400
VO2 (mL/min)
Clear plateau
Subject #2
Subject #3
2000
1600
1200
800
400
0
0
2
4
6
8
10
12
14
16
Time (min)
For 34 subjects, breath-by-breath data with an 11 breath average, and
based on VO2 50 mL/min for VO2max and closest neighboring data
point.
VO plateau incidence = 86%
2
Background
• No universally recommended procedures for
processing VO2 data from breath-by-breath indirect
calorimetry, or from time averaged systems.
• No standardized criteria or recommended methods for
detecting either of a VO2 plateau, the maximal rate of
oxygen consumption (VO2max), or a peak VO2 in the
absence of a VO2 plateau (VO2peak).
• Increasing use of breath-by-breath indirect calorimetry
in education, research and professional practice
• The lack of any objective criteria to follow when
processing decreases the validity of measurement.
VO2max Issues
6
Dr. Robert Robergs
Fall, 2010
Challenges
• How do researchers in exercise physiology currently
collect and process data?
• How long should the protocol be?
• What type of protocol should be used?
• What causes the “noise” in breath-by-breath VO2
data?
• Should this “noise” be reduced? If so, how?
• What is a VO2 plateau?
• How can a VO2 plateau be objectively determined?
• What is VO2max vs. VO2peak?
• How can VO2max and VO2peak be objectively
determined?
VO2 (L/min)
What causes the “noise” in breath-by-breath VO2 data?
3.5
3.0
2.5
2.0
1.5
1.0
VE STPD
(L/min)
2.17  0.3 L/min, with a range of 1.4 – 3.3 L/min
70
55
40
25
10
VO2max Issues
7
Fall, 2010
Variability 96 % explained by a twofactor model of VE and FEO2
Predicted VO2 (L/min)
Dr. Robert Robergs
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0.0
3.5
Pred VO2 = 0.9572(Meas VO2) + 0.0898
R2 = 0.9572
SEE = 0.059 L/min)
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
Measured VO2 (L/min)
VO2 (L/min)
3.0
2.5
2.0
1.5
1.0
Measured
Predicted
0.5
0.0
0
2
4
6
8
10
12
14
Time (min)
Variability Remaining
VO2 (L/min)
2.5
5%error
2.0
1.5
1.0
0.5
0.0
0
2
4
6
8
10
12
14
Time (min)
VO2max Issues
8
Dr. Robert Robergs
Fall, 2010
Should this “noise” be reduced?
YES
How should this “noise” be reduced?
4.5
3.5
VO2 (L/min)
VO2 (L/min)
4
a=bb
4.0
3.0
2.5
2.0
1.5
Time Averaging
b=15 s
3
2
40
e
1
1.0
0.5
60 s
0
5
10
15
0
20
0
Time (min)
4
5
10
15
20
Time (min)
Breaths
30
0.0
20
30 s
4
c=30 s
d=60 s
10
VO2 (L/min)
VO2 (L/min)
15 s
3
2
1
0
0
2
5
10
15
20
Time (min)
1
0
0
5
10
15
Time (min)
VO2max Issues
3
20
0
0
5
10
15
20
Time (min)
9
Dr. Robert Robergs
Fall, 2010
4.5
Breath Averaging
b=5 bre aths
4
3.5
VO2 (L/min)
3.0
2.5
2.0
1.5
3
2
1.75
1.0
1
0.5
0.0
0
0
5
10
15
20
0
5
Time (min)
15
20
Time (min)
4
c=11 breaths
d=21 bre aths
3
VO2 (L/min)
VO2 (L/min)
4
10
2
1
Time Interval (min)
VO2 (L/min)
5
a=bb
4.0
1.50
1.25
21 breaths
1.00
0.75
11 breaths
0.50
5 breaths
0.25
3
bb
0.00
0
2
5
10
15
20
Time (min)
1
0
0
5
10
15
0
20
0
Time (min)
5
10
15
20
Time (min)
4
VO2 (L/min)
a
muscle
Digital Filtering
3
2
1
4
d
VO2 (L/min)
0
4
VO2 (L/min)
b
cardiovascular
3
3
2
1
2
1
0
0
4
e
VO2 (L/min)
c
VO2 (L/min)
ventilation
4
3
2
2
1
1
0
0
0
50
100
150
Data Points
VO2max Issues
3
200
250
0
50
100
150
200
250
Data Points
10
Dr. Robert Robergs
Fall, 2010
Digital Filter Example
What is a VO2 plateau?
linear regress ion
3750
VO2 (mL/min)
4000
VO2 (mL/min)
3500
3000
3500
3250
VO2 plateau
at VO2max
3000
2500
2750
12
13
2000
14
15
16
17
18
Time (min)
initial deviation from linearity
1500
1000
500
exercise
rest
0
0
2
4
6
8
10
12
14
16
18
Time (min)
VO2max Issues
11
Dr. Robert Robergs
Fall, 2010
What is VO2max or VO2peak?
VO2 (L/min)
5
4
3
2
1
0
0
2
4
6
8
10
12
14
16
18
Time (min)
Data Example
treadmill running
VO2 (mL/min)
4000
3600
3200
2800
2400
2000
10
11
12
13
14
15
Time (min)
VO2max Issues
12
Dr. Robert Robergs
Fall, 2010
Conclusions
• Clear rationale for processing breath-by-breath
VO2 data to decrease “noise”.
• Processing best done by digital filtering
• Still formulating and debating criteria and
methods to quantify VO2 plateau, VO2max,
VO2peak
• In the absence of a VO2 plateau, what are valid
criteria to use to verify a “true” VO2max?
VO2max Issues
13