Dr. Robert Robergs Fall, 2010
VO2max Issues 1
VOVO22max Measurement and Analysismax Measurement and AnalysisDr. Robert A. Robergs, Ph.D., EPC, FASEP
Director:Exercise Physiology Laboratories
Exercise Science ProgramThe University of New MexicoAlbuquerque, NM 87131-1258
www.unm.edu/~rrobergs
Early History
Archibald Vivian Hill
“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.”
(Hill A.V. and H. Lupton. QQ J Med 1923; 16:135-171.)
In performing his research, Hill used,• discontinuous running protocols• limited running speeds
• 6-7 subjects
• combined data from multiple subjects
Dr. Robert Robergs Fall, 2010
VO2max Issues 2
Time or Intensity
VO2
VO2max
Cardiorespiratory limitations
What is VO2max
Duration should be ~8-10 min
• 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.
Definitions:
Other “less correct” terms!“aerobic power” “aerobic capacity”
“maximal cardiorespiratory capacity”
Dr. Robert Robergs Fall, 2010
VO2max Issues 3
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.”
Dr. Robert Robergs Fall, 2010
VO2max Issues 4
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...”
Dr. Robert Robergs Fall, 2010
VO2max Issues 5
Determinants of VO2max
Cardiac Output
CENTRAL PERIPHERAL
oxygen delivery capillary density
fiber dimensions
Peripheral Oxygen Diffusion
muscle massPO2 gradients
O2 supply demand relationships
A-aPO2
SaO2
VO2max = Qmax x a-vO2max
[Hb]
HR x SV
Dr. Robert Robergs Fall, 2010
VO2max Issues 6
0 2 4 6 8 10 12 14 160
400
800
1200
1600
2000
2400
2800Subject #2Subject #3
Time (min)
VO2
(mL/
min
)
Plateau???
Clear plateau
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. VO2 plateau incidence = 86%
• 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.
Background
Dr. Robert Robergs Fall, 2010
VO2max Issues 7
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 VO2data?• 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?
1.01.52.02.53.03.5
VO2
(L/m
in)
What causes the “noise” in breath-by-breath VO2 data?
2.17 0.3 L/min, with a range of 1.4 – 3.3 L/min
1025
40
5570
VE S
TPD
(L/m
in)
Dr. Robert Robergs Fall, 2010
VO2max Issues 8
0 2 4 6 8 10 12 14
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
MeasuredPredicted
Time (min)
VO2
(L/m
in)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0 Pred VO2 = 0.9572(Meas VO2) + 0.0898R2 = 0.9572SEE = 0.059 L/min)
Measured VO2 (L/min)
Pred
icte
d VO
2 (L
/min
)
Variability 96 % explained by a two-factor model of VE and FEO2
0 2 4 6 8 10 12 140.0
0.5
1.0
1.5
2.0
2.5
5%error
Time (min)
VO2
(L/m
in)
Variability Remaining
Dr. Robert Robergs Fall, 2010
VO2max Issues 9
Should this “noise” be reduced?
YES
How should this “noise” be reduced?
0 5 10 15 200.00.51.01.52.02.53.03.54.04.5
a=bb
Time (min)
VO2
(L/m
in)
0 5 10 15 200
1
2
3
4b=15 s
Time (min)
VO2
(L/m
in)
0 5 10 15 200
1
2
3
4c=30 s
Time (min)
VO2
(L/m
in)
0 5 10 15 200
1
2
3
4d=60 s
Time (min)
VO2
(L/m
in)
0 5 10 15 200
10
20
30
40
15 s
30 s
60 s
e
Time (min)
Bre
aths
Time Averaging
Dr. Robert Robergs Fall, 2010
VO2max Issues 10
0 5 10 15 200.00.51.01.52.02.53.03.54.04.5
a=bb
Time (min)
VO2
(L/m
in)
0 5 10 15 200
1
2
3
4
5b=5 breaths
Time (min)VO
2 (L
/min
)
0 5 10 15 200
1
2
3
4c=11 breaths
Time (min)
VO2
(L/m
in)
0 5 10 15 200
1
2
3
4d=21 breaths
Time (min)
VO2
(L/m
in)
0 5 10 15 200.00
0.25
0.50
0.75
1.00
1.25
1.50
1.75
21 breaths
11 breaths
5 breaths
bb
Time (min)
Tim
e In
terv
al (m
in)
Breath Averaging
0
1
2
3
4a
VO2
(L/m
in)
0
1
2
3
4d
VO2
(L/m
in)
0
1
2
3
4b
VO2
(L/m
in)
0 50 100 150 200 2500
1
2
3
4e
Data Points
VO2
(L/m
in)
0 50 100 150 200 2500
1
2
3
4c
Data Points
VO2
(L/m
in)
muscle
cardiovascular
ventilation
Digital Filtering
Dr. Robert Robergs Fall, 2010
VO2max Issues 11
Digital Filter Example
0 2 4 6 8 10 12 14 16 180
500
1000
1500
2000
2500
3000
3500
4000
rest exercise
Time (min)
VO2
(mL/
min
)
linear regress ion
initial deviation from linearity
VO2 plateau at VO2max
12 13 14 15 16 17 182750
3000
3250
3500
3750
Time (min)
VO2
(mL/
min
)
What is a VO2 plateau?
Dr. Robert Robergs Fall, 2010
VO2max Issues 12
What is VO2max or VO2peak?
0 2 4 6 8 10 12 14 16 180
1
2
3
4
5
Time (min)
VO2
(L/m
in)
Data Example
10 11 12 13 14 152000
2400
2800
3200
3600
4000treadmill running
Time (min)
VO2
(mL/
min
)
Dr. Robert Robergs Fall, 2010
VO2max Issues 13
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?