Anyone have a reference for how much metabolic efficiency varies among elite cyclists?.
Efficiency varies from 20-25% according to both researchers and PowerTap literature. While 5% may sound like a lot, there is actually not much difference in efficiency between novice and elite cyclists and it is not something that is easy to improve either. In reference 1 below, a significant increase in efficiency was seen throughout the season: 19.6% to 20.6%! More interesting in reference 2, there was an inverse relationship between efficiency and VO2 max in professional cyclists, suggesting that efficiency compensated for a relatively low VO2 max in professional cyclists.
Hopker J, Coleman D, Passfield L. Changes in cycling efficiency during a competitive season. Med Sci Sports Exerc. 2009 Apr;41(4):912-9.
PURPOSE: To monitor training-related changes in gross efficiency (GE) over the course of a competitive cycling season. METHODS: Fourteen trained cyclists (mean +/- SD: 34 + 8 yr, 74.3 +/- 7.4 kg, Wmax = 406 +/- 43 W, V O2max = 59.5 +/- 3.8 mL x kg x min) with at least 3 yr competitive experience completed five laboratory tests during a competitive cycling season. The tests measured lactate threshold (LT), onset of blood lactate accumulation (OBLA), maximal oxygen uptake (V O2max), maximal minute power (Wmax), and GE. The data were analyzed using repeated-measures ANOVA and Pearson's product-moment correlation coefficient. RESULTS: GE changed significantly over the course of the competitive cycling season (P < 0.05), increasing over the precompetition phase of the season (19.6% vs 20.6%; P < 0.05). GE was maintained during the main competitive phase of the season (20.6% vs 20.3%; P > 0.05) and then decreased during the postcompetitive phase to 19.4% (P < 0.05). The precompetition changes in GE were related to the total time spent training and the time spent above OBLA intensity (r = 0.84 and 0.80, respectively). Riders who spent the most time training between LT and OBLA intensities (r = 0.87; P < 0.05) were better able to maintain GE. A significant inverse relationship was also identified between the changes in GE and the percentage change in training below LT over the competitive phase of the season. CONCLUSION: GE changes over the course of a competitive cycling season and is related to the volume and intensity of training conducted.
Lucía A, Hoyos J, Pérez M, Santalla A, Chicharro JL. Inverse relationship between VO2max and economy/efficiency in world-class cyclists. Med Sci Sports Exerc. 2002 Dec;34(12):2079-84
PURPOSE: To determine the relationship that exists between VO2max and cycling economy/efficiency during intense, submaximal exercise in world-class road professional cyclists. METHODS Each of 11 male cyclists (26+/-1 yr (mean +/- SEM); VO2max: 72.0 +/- 1.8 mL x kg(-1) x min(-1)) performed: 1) a ramp test for O2max determination and 2) a constant-load test of 20-min duration at the power output eliciting 80% of subjects' VO2max during the previous ramp test (mean power output of 385 +/- 7 W). Cycling economy (CE) and gross mechanical efficiency (GE) were calculated during the constant-load tests. RESULTS: CE and GE averaged 85.2 +/- 2.3 W x L(-1) x min(-1) and 24.5 +/- 0.7%, respectively. An inverse, significant correlation was found between 1) VO2max (mL x kg(-0.32) x min(-1)) and both CE (r = -0.71; P = 0.01) and GE (-0.72; P = 0.01), and 2) VO2max (mL x kg(-1) x min(-1)) and both CE (r = -0.65; P = 0.03) and GE (-0.64; P = 0.03). CONCLUSIONS: A high CE/GE seems to compensate for a relatively low VO2max in professional cyclists.