Cycling efficiency (efficiently)

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Webinar for USA Cycling Coaching Education program.

Webinar for USA Cycling Coaching Education program.

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  • 1. Cycling efficiency (efficiently): what does it really mean? Andrew R. Coggan, Ph.D. Cardiovascular Imaging Laboratory Washington University School of Medicine St. Louis, MO 63110
  • 2. Cycling efficiency • • • • • What is it? How do you measure it? Why is it important? What determines it? How do you train it?
  • 3. Cycling efficiency – what is it? Definition • The same as in other scientific fields, e.g., physics: energy out/energy in x 100% Related concepts • Net efficiency, delta efficiency, economy
  • 4. Cycling efficiency – how do you measure it? • Only one way to do so: → by using a metabolic chamber or cart to quantify energy liberation via direct or indirect calorimetry while simultaneously measuring power output using a cycle ergometer (or bicycle-mounted power meter).
  • 5. Direct versus indirect calorimetry
  • 6. Sample calculation of efficiency • Power (energy out) = 159 W (159 J/s) • VO2 = 2.16 L/min • RER = 0.82 • Energy in = 2.16 L/min x 4.825 kCal/L x 4184 J/kCal x 1 min/60 s = 728 J/s • Efficiency = energy out/energy in x 100% • Efficiency = 159 J/s x 1/728 J/s x 100% = 21.8%
  • 7. Effect of absolute power output on gross efficiency
  • 8. Cycling efficiency – why is it important? • Cycling efficiency represents the link between ATP turnover and external power output. • Thus, for a given metabolic rate a more efficient individual will be able to produce more power, and/or will be able to produce a given power output at a lower metabolic rate (= less physiological strain).
  • 9. Effect of cycling economy on performance (“hour power”) Horowitz, Sidossis, and Coyle. Int J Sports Med 1994; 15:152-157
  • 10. Variations in efficiency in world class cyclists Lucia et al. Med Sci Sports Exerc 2002; 34:2079-2084
  • 11. Cycling efficiency – what determines it? Biomechanical factors • • • • • Saddle height Cadence (speed of muscle shortening) Not crank length Not fore-aft position of foot Not pattern of force application Biochemical factors • Muscle fiber type • UCP3 • SERCA1/SERCA 2
  • 12. Biomechanical factors
  • 13. Effect of saddle height on efficiency Price and Donne J Sports Sci 1997; 15:395-402
  • 14. Effect of cadence on economy Hagberg et al. J Appl Physiol 1981; 51:447-451
  • 15. Effect of crank length on efficiency McDaniel et al. J Appl Physiol 2002; 93:823-828
  • 16. Effect of foot position on economy Sickle and Hull J Biomech 2007; 40:1262-1267
  • 17. The classic “clock diagram” of pedaling forces
  • 18. Evidence that increasing mechanical effectiveness does not improve cycling efficiency • Theoretical considerations – Role of uniarticular and biarticular muscles (Kautz and Neptune Exerc Sports Sci Rev 2002; 30:159-165) • Cross-sectional observations – On average, pattern of force application very similar in trained and untrained persons (Morneiux et al. Int J Sports Med 2008; 29:817-822)
  • 19. Pattern of force application in elite cyclists vs. non-cyclists Mornieux et al. Int J Sports Med 2008; 29:817-822
  • 20. Evidence that increasing mechanical effectiveness does not improve cycling efficiency • Theoretical considerations – Role of uniarticular and biarticular muscles (Kautz and Neptune Exerc Sports Sci Rev 2002; 30:159-165) • Cross-sectional observations – On average, pattern of force application very similar in trained and untrained persons (Morneiux et al. Int J Sports Med 2008; 29:817-822) – Inverse relationship between min:max torque and gross (R2 = -0.72; P<0.001) or delta (R2 = -0.76; P<0.001) efficiency (Edwards et al. J Sports Sci 2009; 27:319-325) – Individuals can be very efficient despite unusual pattern of force application (continued)
  • 21. Unusual pattern of force application in a champion cyclist (rider 2)
  • 22. Evidence that increasing mechanical effectiveness does not improve cycling efficiency • Longitudinal (interventional) observations – Removing toe-clips and cleats does not reduce efficiency (Coyle et al. J Appl Physiol 1988; 64:2622-2630, Ostler et al. J Sports Sci 2008; 26:47-55) – Training using uncoupled cranks does not improve efficiency (Bohm et al. Eur J Appl Physiol 2008; 103:225-232, Williams et al. Int J Sports Physiol Perform 2009; 4:18-28) – Acutely altering pedal stroke to be “rounder” reduces efficiency (Korff et al. Med Sci Sports Exerc 2007; 39:991-995)
  • 23. Effect of pattern of force application on efficiency Korff et al. Med Sci Sports Exerc 2007; 39:991-995
  • 24. Effect of pattern of force application on efficiency Korff et al. Med Sci Sports Exerc 2007; 39:991-995
  • 25. Biochemical factors
  • 26. Effect of fiber type on efficiency Coyle et al. Med Sci Sports Exerc 1992; 24:782-788
  • 27. Effect of UCP3 on efficiency Mogensen et al. J Physiol 2006; 571.3:669-681
  • 28. Effect of training on P:O ratio Mogensen et al. J Physiol 2006; 571.3:669-681
  • 29. Effect of training on SERCA1/SERCA2 and efficiency Majerczak et al. J Physiol Pharmacol 2008; 59:589-602
  • 30. Cycling efficiency – how do you train it?
  • 31. Cycling efficiency – can it be trained?
  • 32. Cross-sectional studies of cycling efficiency No difference • • • • • Boning et al. Int J Sports Med 1984; 5:92-97 Marsh and Martin Med Sci Sports Exerc 1993; 25:1269-1274 Nickleberry and Brooks Med Sci Sports Exerc 1996; 28:1396-1401 Marsh et al. Med Sci Sports Exerc 2000; 32:1630-1634 Mosely et al. Int J Sports Med 2004; 25:374-379 Higher in trained cyclists • • Sallet P et al. J Sports Med Fitness 2006; 46:361-365 Hopker et al. Appl Physiol Nutr Metab 2007; 32:1036-1042
  • 33. Longitudinal studies of cycling efficiency No change • Roels et al. Med Sci Sports Exerc 2005; 37:138-146 Increases with training • • • • • • • Hintzy et al. Can J Appl Physiol 2005; 30:520-528 Paton and Hopkins J Strength Cond Res 2005; 13:826-830 Majerczak et al. J Physiol Pharmacol 2008; 59:589-602 Sassi et al. Appl Physiol Nutr Metab 2008; 33:735-742 Hopker et al. Med Sci Sports Exerc 2009; 41:912-919 Hopker et al. Appl Physiol Nutr Metab 2010; 35:17-22 Sunde et al. J Strength Cond Res 2010 (in press)
  • 34. Cycling efficiency – how do you train it? • “Ordinary” training apparently results in a small, but significant, improvement in cycling efficiency. However, whether efficiency continues to improve over many years or merely oscillates in/out of season around some average value is still uncertain. (continued)
  • 35. Cycling efficiency – how do you train it? (con’t) • Additional improvements might be obtained via “special techniques”, i.e.,: – High intensity training – – – Paton and Hopkins J Strength Cond Res 2005; 13:826-830 Hopker et al. Med Sci Sports Exerc 2009; 41:912-919 Hopker et al. Appl Physiol Nutr Metab 2010; 35:17-22 – Training in hypoxia – – Gore et al. Acta Physiologica Scandinavica 2001; 173:275286 Katayama et al. High Alt Med Biol 2003; 4:291-304 – Resistance training – Sunde et al. J Strength Cond Res 2010 (in press)
  • 36. Key Points Cycling efficiency  Is defined as energy out/energy in x 100%;  Can only be determined via use of direct or indirect calorimetry in conjunction with power measurements;  Represents the link between cellular energy “production” and actual performance (i.e., power); (continued)
  • 37. Key Points (continued) Cycling efficiency  Can vary significantly between individuals, even among world class cyclists;  Is apparently determined by both biomechanical (i.e., saddle height, cadence) and biochemical (i.e., fiber type, SERCA activity) factors;  Is either not related to, or is even inversely related to, mechanical effectiveness; (continued)
  • 38. Key Points (continued) Cycling efficiency  Improves as a function of “ordinary” endurance training;  Might be further increased with very prolonged and/or very intense training, and/or as a result of hypoxia or resistance training