laboratory based testing
DESCRIPTION
Webinar for USA Cycling Coaching Education program.TRANSCRIPT
Laboratory-based testingof competitive cyclists
Andrew R. Coggan, Ph.D.
Cardiovascular Imaging Laboratory
Washington University School of Medicine
St. Louis, MO 63021
Laboratory-based testing• What is it?
– For purposes of this seminar, anything done indoors!
• Why should you do it (compared to using a field test)?– Controlled environment– Submaximal testing possible– Can obtain greater insight into athlete’s strengths and weaknesses and/or
effectiveness of training program– Not necessarily more accurate/precise
• Why should you not do it?– Cost– Convenience (may interfere with routine training)– Psychological factors
• When should you do it?– Depends on many factors, but frequent testing not necessarily better
• How do you do it?
Determinants of endurance performance
Maximal oxygen consumption (VO2max)
• What is it?– The highest rate of oxygen uptake (VO2) achievable during exercise
that utilizes a large muscle mass (e.g., running).
• Why is it important?– VO2max is the best overall measure of cardiovascular fitness and
sets the upper limit to the production of energy (ATP) via aerobic metabolism (i.e., mitochondrial respiration). As such, having a high VO2max is a necessary but not a sufficient condition to be an elite endurance athlete.
• How do you measure it?– By using a “metabolic cart” (gas analyzers, flow measuring device)
to quantify respiratory gas exchange (VO2, CO2 production (VCO2)) across the lungs/at the mouth during an incremental exercise test.
• Related concepts– VO2peak, RER
Subject performing VO2max test
Calculation of VO2, VCO2, and RER
VO2 = rate of O2 uptake (L/min or mL/min/kg)..
VCO2 = rate of CO2 release (L/min or mL/min/kg)..
VO2 = (VI • FIO2) - (VE • FEO2). . .
VCO2 = (VE • FECO2) - (VI • FICO2). . .
Where VE = expired ventilation; VI = inspired ventilation; FIO2 = fraction of oxygen inspired; FICO2 = fraction of carbon dioxide inspired; FEO2 = fraction of oxygen expired; and FECO2 = fraction of carbon dioxide expired.
. .RER = VCO2 / VO2
. .
Characteristics of “ideal” VO2max test
• Total duration 8-12 min• Stages typically 1-3 min in length
• Exercise intensity increased by <5-8% of VO2max per stage, at least towards end of test
• For athletes, sports-specific mode of exercise: cyclists cycling
Criteria for determination/definition of VO2max
• Absolute or relative plateau in VO2 despite increase in O2 demand (e.g., <150 mL/min or <1.5 mL/min/kg increase between stages)
• RER > 1.10
• Heart rate w/in 10 beats/min of age-predicted maximum
• Blood lactate concentration > 8 mmol/L
• Volitional fatigue is not evidence that VO2max has been achieved!
VO2 and heart rate vs. power
0
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6
0 50 100 150 200 250 300 350 400 450
Power (W)
VO
2 (L
/min
))
0
20
40
60
80
100
120
140
160
180
HR
(beats/m
in)
VO2 Heart rate
Role of genetics in determining baseline VO2max
Role of genetics in determining change in VO2max with training
Lactate threshold (LT)
• What is it?– The exercise intensity at which lactate production exceeds lactate
utilization, such that lactate begins to accumulate in muscle and hence blood.
• Why is it important?– LT is the best measure of metabolic fitness and determines the
fraction of VO2max that may be sustained for any duration from a few minutes to many hours. LT is therefore the most important physiological factor determining endurance exercise performance.
• How do you measure it?– By obtaining blood samples to quantify lactate concentrations
during an incremental exercise test.
• Related concepts– Onset of blood lactate accumulation (OBLA), maximal lactate
steady state (MLSS), individual anaerobic threshold (IAT), lactate minimum (lactate balance point), ventilatory (anaerobic) threshold (VT/AT), critical power.
LT test results for a cyclist-turned-duathlete
OBLA
LT
Blood [lactate] as a function of time during exercise at a constant power
Subject BL
0
1
2
3
4
5
6
0 2 4 6 8 10
Time (min)
Blo
od
HL
a (
mm
ol/L
)
245 W
275 W
310 W
325 W
Time to fatigue @ 310 W: 58 min
Blood [lactate] as a function of time during exercise at a constant power
Subject AC
0
1
2
3
4
5
6
0 2 4 6 8 10Time (min)
Blo
od
HL
a (
mm
ol/L
)
260 W
295 W
310 W
345 W
Time to fatigue @ 325 W: 75 min
Blood [lactate] as a function of time during exercise at a constant power
Subject GC
0
1
2
3
4
5
6
0 2 4 6 8 10
Time (min)
Blo
od
HL
a (
mm
ol/L
)
210 W
245 W
275 W
310 W
Time to fatigue @ 310 W: 22 min
Determination of ventilatory (“anaerobic”) threshold (VT) based on ventilation (Ve)
Determination of VT based on ventilatory equivalents (Ve/VO2 and Ve/VCO2)
Determination of critical power(hyperbolic model)
0
600
1200
1800
2400
3000
3600
0 50 100 150 200 250 300 350 400 450 500 550 600
Power (W)
Tim
e (s
)
y = 24757 / (262 - x)
R2 = 0.998
Anaerobic work capacity (in J)
Critical power (in W)
Determination of critical power(linear model)
y = 263x + 22951
R2 = 0.99998
0
250,000
500,000
750,000
0 600 1200 1800 2400 3000 3600
Time (s)
Wor
k (J
)
Slope = critical power (in W)
Intercept = anaerobic work capacity (in J)
Gross efficiency (GE)
• What is it?– The ratio of work out/energy in x 100%.
• Why is it important?– Gross efficiency determines the power output corresponding to a
exercise at a given percentage of VO2max and/or LT.
• How do you measure it?– By quantifying energy production via indirect calorimetry
(respiratory gas exchange) in relation to power output on a cycle ergometer.
• Related concepts– Net efficiency, delta efficiency, economy,
Power-VO2 relationship (economy/efficiency)
y = 0.0106x + 0.45
R2 = 0.998
y = 0.0112x + 0.45
R2 = 0.997
0
1
2
3
4
5
0 50 100 150 200 250 300 350 400
Power (W)
VO
2 (L
/min
)
Energy yield and relative contribution of carbohydrate and fat calculated from RER
0.71 4.69 0.0 100.0
0.75 4.74 15.6 84.4
0.80 4.80 33.4 66.6
0.85 4.86 50.7 49.3
0.90 4.92 67.5 32.5
0.95 4.99 84.0 16.0
1.00 5.05 100.0 0.0
RER kcal/L O2 Carbohydrates Fats
Energy yield % kcal from
Effect of VO2 “drift” on power-VO2 relationship
Power-VO2 relationship (economy/efficiency)
y = 0.0106x + 0.45
R2 = 0.998
y = 0.0112x + 0.45
R2 = 0.997
0
1
2
3
4
5
0 50 100 150 200 250 300 350 400
Power (W)
VO
2 (L
/min
)
Muscle fiber type, cycling economy,and ‘hour power’
From: Horowitz JF, Sidossis LS, Coyle EF. High efficiency of type I fibers improves performance. Int. J. Sports Med. 15:152, 1994.
Determinants of “anaerobic” performance
Performance abilities
Functional abilities
Physiological determinants
Performance velocity
Performance power
Resistance to movement
Efficiency / economy
Neuromuscular power
Anaerobic capacity
Neural control
Fiber type (% type II)
Muscle buffer capacity
Muscle mass
Neuromuscular power
• What is it?– Maximum power developed by muscle in unfatigued state – limited
by rate of energy utilization (i.e., rate of ATP hydrolysis), not energy production.
• Why is it important?– High power obviously critical to achieve high speed/rapid
acceleration (e.g., sprinting, standing start).
• How do you measure it?– No gold standard exists, but inertial load method is probably the
most convenient and accurate approach.
• Related concepts– Wingate peak power
Anaerobic capacity
• What is it?– The maximum amount of work (not the rate of doing such work, i.e,
power) that can be performed using ATP produced via anaerobic metabolism.
• Why is it important?– Sustained efforts at supramaximal (I.e., requiring >100% of
VO2max) intensities obviously critical in many races/race situations (e.g., pursuit, bridging gaps, shorter hills).
• How do you measure it?– Again, no true gold standard exists, but maximal accumulated O2
deficit (MAOD) probably comes closest. MAOD is determined by measuring the difference between O2 demand and O2 uptake during exercise to fatigue at 110% of VO2max.
• Related concepts– Wingate average power, anaerobic work capacity (AWC)
determined using critical power approach.
The classic Wingate test
1. Warm-up at a moderate intensity for 3-5 min.
2. Pedal Monark ergometer “all out” against no resistance.
3. Within 3 s, apply braking force of 0.075 kg/kg body mass and start timing.
4. Record number of pedal revolutions completed every 5 s for 30 s.
5. Warm down for at least 2 min.
6. Optional: go puke in wastebasket!
Data derived from Wingate test
1. Peak power (first 5 s) in W =
braking force (kg) x 9.81 N/kg x 6 m/rev x revolutions/5 s
2. Mean power (30 s) in W =
braking force (kg) x 9.81 N/kg x 6 m/rev x revolutions/30 s
3. Fatigue index in % =
(peak power – power during last 5 s)/peak power x 100%
Normal values and percentile rankings for mean power during a Wingate test
Maud & Schultz, Research Quarterly. Vol 60 pp 144-149. 1989 Males (N=60) and Females (N=69)
Watts W•kgBW-1 Percentile Rank Male Female Male Female 95 676.6 483.0 8.63 7.52 90 661.8 469.9 8.24 7.31 85 630.5 437.0 8.09 7.08 80 617.9 419.4 8.01 6.95 75 604.3 413.5 7.96 6.93 70 600.0 409.7 7.91 6.77 65 591.7 402.2 7.70 6.65 60 576.8 391.4 7.59 6.59 55 574.5 386.0 7.46 6.51 50 564.6 381.1 7.44 6.39 45 552.8 376.9 7.26 6.20 40 547.6 366.9 7.14 6.15 35 534.6 360.5 7.08 6.13 30 529.7 353.2 7.00 6.03 25 520.6 346.8 6.79 5.94 20 496.1 336.5 6.59 5.71 15 484.6 320.3 6.39 5.56 10 470.9 306.1 5.98 5.25 5 453.2 286.5 5.56 5.07 Mean 562.7 380.8 7.28 6.35 Minmum 441.3 235.4 4.63 4.53 Maximum 711.0 528.6 9.07 8.11 SD 66.5 56.4 .88 .73
Advantages and disadvantages of Wingate test
• Advantages– Simple– Common– Relevant
• Disadvantages– Strenuous– Not a ‘pure’ test of anything:
• Typically underestimates true neuromuscular power
• Does not really measure anaerobic capacity
• Aerobic contribution significant in endurance trained cyclists
Maximal power as a function of cadence
Jim Martin’s inertial load ergometer
Example of data obtained from inertial load test
Difference between O2 deficit and O2 debt (Excess Post-Exercise Oxygen Consumption)
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100
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400
500
600
700
800
900
0 30 60 90 120 150 180 210 240
Time (seconds)
Po
we
r (W
)Role of VO2max, gross efficiency, MAOD, and
aerodynamic drag characteristics (CdA) in determining 3 km pursuit performance
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800
900
0 30 60 90 120 150 180 210 240
Time (seconds)
Po
we
r (W
)
VO2max = 4.45 L/min
G.E. = 24.1%
Est. MAOD = 3.09 L
Ave. power = 390 W
CdA = 0.204 m2
3 km time = 3:47.3
VO2max = 4.20 L/min
G.E. = 23.9%
Est. MAOD = 5.11 L
Ave. power = 411 W
CdA = 0.236 m2
3 km time = 3:49.7
Rider A Rider B
Total Total
Maximal aerobic Maximal aerobic82%72%
28% 18%
Determination of critical power(hyperbolic model)
0
600
1200
1800
2400
3000
3600
0 50 100 150 200 250 300 350 400 450 500 550 600
Power (W)
Tim
e (s
)
y = 24757 / (262 - x)
R2 = 0.998
Anaerobic work capacity (in J)
Critical power (in W)
Determination of critical power(linear model)
y = 263x + 22951
R2 = 0.99998
0
250,000
500,000
750,000
0 600 1200 1800 2400 3000 3600
Time (s)
Wor
k (J
)
Slope = critical power (in W)
Intercept = anaerobic work capacity (in J)