Laboratory based testing

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Webinar for USA Cycling Coaching Education program.

Webinar for USA Cycling Coaching Education program.

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  • 1. Laboratory-based testing of competitive cyclists Andrew R. Coggan, Ph.D. Cardiovascular Imaging Laboratory Washington University School of Medicine St. Louis, MO 63021
  • 2. 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?
  • 3. Determinants of endurance performance
  • 4. 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
  • 5. Subject performing VO2max test
  • 6. 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) . . RER = VCO2 / VO2 . . 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.
  • 7. 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
  • 8. Criteria for determination/definition of VO 2max • 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!
  • 9. VO2 and heart rate vs. power VO2 Heart rate 180 6 160 140 120 4 100 3 80 60 2 40 1 20 0 0 0 50 100 150 200 250 Power (W) 300 350 400 450 HR (beats/min) VO 2 (L/min)) 5
  • 10. Role of genetics in determining baseline VO2max
  • 11. Role of genetics in determining change in VO2max with training
  • 12. 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.
  • 13. LT test results for a cyclist-turned-duathlete OBLA LT
  • 14. Blood [lactate] as a function of time during exercise at a constant power Subject BL 6 Blood HLa (mmol/L) 5 4 245 W 275 W 310 W 325 W Time to fatigue @ 310 W: 58 min 3 2 1 0 0 2 4 6 Time (min) 8 10
  • 15. Blood [lactate] as a function of time during exercise at a constant power Subject AC 6 Blood HLa (mmol/L) 5 Time to fatigue @ 325 W: 75 min 4 260 W 295 W 310 W 345 W 3 2 1 0 0 2 4 6 Time (min) 8 10
  • 16. Blood [lactate] as a function of time during exercise at a constant power Subject GC 6 Blood HLa (mmol/L) 5 4 210 W 245 W 275 W 310 W Time to fatigue @ 310 W: 22 min 3 2 1 0 0 2 4 6 Time (min) 8 10
  • 17. Determination of ventilatory (“anaerobic”) threshold (VT) based on ventilation (Ve)
  • 18. Determination of VT based on ventilatory equivalents (Ve/VO2 and Ve/VCO2)
  • 19. Determination of critical power (hyperbolic model) 3600 3000 y = 24757 / (262 - x) R2 = 0.998 Time (s) 2400 Critical power (in W) 1800 1200 Anaerobic work capacity (in J) 600 0 0 50 100 150 200 250 300 350 400 450 500 550 600 Power (W )
  • 20. Determination of critical power (linear model) Work (J) 750,000 y = 263x + 22951 R2 = 0.99998 500,000 Slope = critical power (in W) 250,000 Intercept = anaerobic work capacity (in J) 0 0 600 1200 1800 Time (s) 2400 3000 3600
  • 21. 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,
  • 22. Power-VO2 relationship (economy/efficiency) 5 y = 0.0112x + 0.45 R2 = 0.997 VO2 (L/min) 4 y = 0.0106x + 0.45 R2 = 0.998 3 2 1 0 0 50 100 150 200 Power (W) 250 300 350 400
  • 23. Energy yield and relative contribution of carbohydrate and fat calculated from RER Energy yield % kcal from RER kcal/L O2 Carbohydrates Fats 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
  • 24. Effect of VO2 “drift” on power-VO2 relationship
  • 25. Power-VO2 relationship (economy/efficiency) 5 y = 0.0112x + 0.45 R2 = 0.997 VO2 (L/min) 4 y = 0.0106x + 0.45 R2 = 0.998 3 2 1 0 0 50 100 150 200 Power (W) 250 300 350 400
  • 26. 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.
  • 27. Determinants of “anaerobic” performance Performance velocity Resistance to movement Performance power Performance abilities Efficiency / economy Neuromuscular power Neural control Fiber type (% type II) Anaerobic capacity Muscle mass Functional abilities Muscle buffer capacity Physiological determinants
  • 28. 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
  • 29. 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.
  • 30. 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!
  • 31. 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%
  • 32. 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) Percentile Rank 95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 Mean Minmum Maximum SD Watts Male 676.6 661.8 630.5 617.9 604.3 600.0 591.7 576.8 574.5 564.6 552.8 547.6 534.6 529.7 520.6 496.1 484.6 470.9 453.2 562.7 441.3 711.0 66.5 Female 483.0 469.9 437.0 419.4 413.5 409.7 402.2 391.4 386.0 381.1 376.9 366.9 360.5 353.2 346.8 336.5 320.3 306.1 286.5 380.8 235.4 528.6 56.4 W•kgBW-1 Male Female 8.63 7.52 8.24 7.31 8.09 7.08 8.01 6.95 7.96 6.93 7.91 6.77 7.70 6.65 7.59 6.59 7.46 6.51 7.44 6.39 7.26 6.20 7.14 6.15 7.08 6.13 7.00 6.03 6.79 5.94 6.59 5.71 6.39 5.56 5.98 5.25 5.56 5.07 7.28 6.35 4.63 4.53 9.07 8.11 .88 .73
  • 33. 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
  • 34. Maximal power as a function of cadence
  • 35. Jim Martin’s inertial load ergometer
  • 36. Example of data obtained from inertial load test
  • 37. Difference between O2 deficit and O2 debt (Excess Post-Exercise Oxygen Consumption)
  • 38. Role of VO2max, gross efficiency, MAOD, and aerodynamic drag characteristics (CdA) in determining 3 km pursuit performance Rider A 900 Total VO2max = 4.45 L/min 800 G.E. = 23.9% Est. MAOD = 5.11 L Ave. power = 411 W 600 600 CdA = 0.236 m2 500 3 km time = 3:49.7 400 28% 300 200 G.E. = 24.1% Total 700 Power (W) 700 Power (W) 900 VO2max = 4.20 L/min 800 Rider B Ave. power = 390 W CdA = 0.204 m2 500 3 km time = 3:47.3 400 18% 300 200 Maximal aerobic 72% 100 Est. MAOD = 3.09 L Maximal aerobic 82% 100 0 0 0 30 60 90 120 150 Time (seconds) 180 210 240 0 30 60 90 120 150 Time (seconds) 180 210 240
  • 39. Determination of critical power (hyperbolic model) 3600 3000 y = 24757 / (262 - x) R2 = 0.998 Time (s) 2400 Critical power (in W) 1800 1200 Anaerobic work capacity (in J) 600 0 0 50 100 150 200 250 300 350 400 450 500 550 600 Power (W )
  • 40. Determination of critical power (linear model) Work (J) 750,000 y = 263x + 22951 R2 = 0.99998 500,000 Slope = critical power (in W) 250,000 Intercept = anaerobic work capacity (in J) 0 0 600 1200 1800 Time (s) 2400 3000 3600