Webinar for USA Cycling Coaching Education program.

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
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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
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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
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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
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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
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Roels et al. Med Sci Sports Exerc 2005; 37:138-146
Increases with training
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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
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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
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Gore et al. Acta Physiologica Scandinavica 2001; 173:275286
Katayama et al. High Alt Med Biol 2003; 4:291-304
– Resistance training
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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