laboratory based testing

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Laboratory-based testing of competitive cyclists Andrew R. Coggan, Ph.D. Cardiovascular Imaging Laboratory Washington University School of Medicine St. Louis, MO 63021

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Webinar for USA Cycling Coaching Education program.

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Page 1: Laboratory based testing

Laboratory-based testingof competitive cyclists

Andrew R. Coggan, Ph.D.

Cardiovascular Imaging Laboratory

Washington University School of Medicine

St. Louis, MO 63021

Page 2: Laboratory based testing

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?

Page 3: Laboratory based testing

Determinants of endurance performance

Page 4: Laboratory based testing

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

Page 5: Laboratory based testing

Subject performing VO2max test

Page 6: Laboratory based testing

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

. .

Page 7: Laboratory based testing

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

Page 8: Laboratory based testing

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!

Page 9: Laboratory based testing

VO2 and heart rate vs. power

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0 50 100 150 200 250 300 350 400 450

Power (W)

VO

2 (L

/min

))

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20

40

60

80

100

120

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HR

(beats/m

in)

VO2 Heart rate

Page 10: Laboratory based testing

Role of genetics in determining baseline VO2max

Page 11: Laboratory based testing

Role of genetics in determining change in VO2max with training

Page 12: Laboratory based testing

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.

Page 13: Laboratory based testing

LT test results for a cyclist-turned-duathlete

OBLA

LT

Page 14: Laboratory based testing

Blood [lactate] as a function of time during exercise at a constant power

Subject BL

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Time (min)

Blo

od

HL

a (

mm

ol/L

)

245 W

275 W

310 W

325 W

Time to fatigue @ 310 W: 58 min

Page 15: Laboratory based testing

Blood [lactate] as a function of time during exercise at a constant power

Subject AC

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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

Page 16: Laboratory based testing

Blood [lactate] as a function of time during exercise at a constant power

Subject GC

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Time (min)

Blo

od

HL

a (

mm

ol/L

)

210 W

245 W

275 W

310 W

Time to fatigue @ 310 W: 22 min

Page 17: Laboratory based testing

Determination of ventilatory (“anaerobic”) threshold (VT) based on ventilation (Ve)

Page 18: Laboratory based testing

Determination of VT based on ventilatory equivalents (Ve/VO2 and Ve/VCO2)

Page 19: Laboratory based testing

Determination of critical power(hyperbolic model)

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3600

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Power (W)

Tim

e (s

)

y = 24757 / (262 - x)

R2 = 0.998

Anaerobic work capacity (in J)

Critical power (in W)

Page 20: Laboratory based testing

Determination of critical power(linear model)

y = 263x + 22951

R2 = 0.99998

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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)

Page 21: Laboratory based testing

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,

Page 22: Laboratory based testing

Power-VO2 relationship (economy/efficiency)

y = 0.0106x + 0.45

R2 = 0.998

y = 0.0112x + 0.45

R2 = 0.997

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0 50 100 150 200 250 300 350 400

Power (W)

VO

2 (L

/min

)

Page 23: Laboratory based testing

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

Page 24: Laboratory based testing

Effect of VO2 “drift” on power-VO2 relationship

Page 25: Laboratory based testing

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

)

Page 26: Laboratory based testing

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.

Page 27: Laboratory based testing

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

Page 28: Laboratory based testing

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

Page 29: Laboratory based testing

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.

Page 30: Laboratory based testing

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!

Page 31: Laboratory based testing

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%

Page 32: Laboratory based testing

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

Page 33: Laboratory based testing

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

Page 34: Laboratory based testing

Maximal power as a function of cadence

Page 35: Laboratory based testing

Jim Martin’s inertial load ergometer

Page 36: Laboratory based testing

Example of data obtained from inertial load test

Page 37: Laboratory based testing

Difference between O2 deficit and O2 debt (Excess Post-Exercise Oxygen Consumption)

Page 38: Laboratory based testing

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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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Time (seconds)

Po

we

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)

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%

Page 39: Laboratory based testing

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)

Page 40: Laboratory based testing

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)