un peu de biblio ne fait pas de mal... :
d'ailleurs le débat est clos puisque l'étude de Coyle vient d'être contreversée dans un article récent (2008)
J Appl Physiol 105: 1020, 2008; doi:10.1152/japplphysiol.90459.2008
8750-7587/08
LETTER TO THE EDITOR
Delta efficiency calculation in Tour de France champion is wrong
TO THE EDITOR: We previously raised concerns (6) about the methodology used to assess Lance Armstrong's muscle efficiency in the popular Journal of Applied Physiology paper entitled "Improved muscle efficiency displayed as Tour de France champion matures" (1). Subsequently, Coyle made available raw data from the January 1993 test that revealed several additional deviations from the published methodology. Coyle used a 20-min ergometer protocol (not 25 min), including 2- and 3-min stages where respiratory exchange ratios (RER) exceeded 1.00. An RER >1.00 invalidates use of the Lusk equations (5) to estimate energy expenditure.
A review of the raw data established that the published delta efficiency (DE) values in the Armstrong paper were calculated using the wrong equation. Coyle's published methodology (1) and that used by his group on several previous occasions (2, 4, 7) stipulates that linear regression (y = mx + b) be used to calculate DE, as the reciprocal of the slope from the relationship between the energy equivalent of oxygen uptake and cycling power output. However, Coyle calculated DE using the general formula 100 x (X x Y)/(X2). This calculation is equivalent to linear regression using y = mx, which forces the regression line through the origin. Resting metabolic rate (RMR) as well as the cost of cycling without load (including the variable cost of ventilation and circulation) mandate that the regression line used to calculate DE cannot pass through the origin.
In their benchmark paper, Gaesser and Brooks (3) argue that DE, as the first derivative of the increase in caloric cost of exercise with respect to ordered increases in work, is a "floating base-line" method. Hence it is essential that the regression is not forced through zero when calculating DE. By employing y = mx for each of the four data sets used to calculate DE, Coyle has assumed that Armstrong's RMR and cost of cycling without a load was not influenced by orchiectomy and chemotherapy, plus well-publicized weight fluctuations during the 7-year study.
Gross efficiency values reported by Coyle, which demonstrate an r = 0.999 correlation with his DE data, have been cogently dismissed by Gaesser and Brooks (3) as being of little value in understanding muscular efficiency. This interpretation is recognized by Coyle who notes on p. 2194 of his publication (1), "delta efficiency ... provides the best reflection of power production ... as it eliminates or minimizes the influence of the energy cost of unloaded cycling, ventilatory work, and other metabolic processes not directly linked to muscle power production."
Using the correct equation, we recalculated Armstrong's DE as 23.55% in January 1993 (23.02% if the 2-min stage is included), which exceeds the 23.12% value for the final test in November 1999. This is 8% higher than the reported value of 21.75%. The magnitude of this error warrants recalculation of the entire data set, but raw data from the remaining test sessions are not available from the author.
In conclusion, all of the published delta efficiency values are wrong. Thus there exists no credible evidence to support Coyle's conclusion that Armstrong's muscle efficiency improved.
FOOTNOTES
Address for reprint requests and other correspondence: C. J. Gore, Australian Institute of Sport, PO Box 176, Belconnen ACT 2616, Australia
REFERENCES
Coyle EF. Improved muscular efficiency displayed as Tour de France champion matures. J Appl Physiol 98: 2191–2196, 2005.[Abstract/Free Full Text]
Coyle EF, Sidossis LS, Horowitz JF, Beltz JD. Cycling efficiency is related to the percentage of type I muscle fibers. Med Sci Sports Exerc 24: 782–788, 1992.[ISI][Medline]
Gaesser GA, Brooks GA. Muscular efficiency during steady-rate exercise: effects of speed and work rate. J Appl Physiol 38: 1132–1139, 1975.[Abstract/Free Full Text]
Horowitz JF, Sidossis LS, Coyle EF. High efficiency of type I muscle fibers improves performance. Int J Sports Med 15: 152–157, 1994.[ISI][Medline]
Lusk G. In: The Elements of the Science of Nutrition. New York: Johnson Reprint, 1976, p. 65.
Martin DT, Quod MJ, Gore CJ, Coyle EF. Has Armstrong's cycle efficiency improved? J Appl Physiol 99: 1628–1629, 2005.[Abstract/Free Full Text]
Sidossis LS, Horowitz JF, Coyle EF. Load and velocity of contraction influence gross and delta mechanical efficiency. Int J Sports Med 13: 407–411, 1992.[ISI][Medline]
Christopher J. Gore1,2
Michael J. Ashenden3
Ken Sharpe4
David T. Martin1
1Department of Physiology, Australian Institute of Sport, Canberra; 2Exercise Physiology Laboratory, School of Education, Flinders University, Adelaide; 3Science and Industry Against Blood-Doping (SIAB) Research Consortium, Gold Coast; and 4Department of Mathematics and Statistics, The University of Melbourne, Melbourne, Australia
Et de toutes façon certains avaient déjà émis des doutes sur la validités de l'étude (et des études de Coyle, sur le phénomène Armstrong) en 2005 :
Il y eu a l'article "Improved muscular efficiency displayed as Tour de France champion matures" de Coyle, 3 "Author reply", dont la dernière (2008 dont l'abstract est publié ci dessus) à fait l'objet d'un papier... sans répone de Coyle pour le moment.J Appl Physiol 99: 1630-1631, 2005; doi:10.1152/japplphysiol.00563.2005
8750-7587/05
Scientific considerations for physiological evaluations of elite athletes
Yorck Olaf Schumacher, Stefan Vogt, Kai Roecker and Andreas Schmid
Department of Sportmedizin
Medizinische Universitaetsklinik Freiburg
79106 Freiburg, Germany
ABSTRACT
This case describes the physiological maturation from ages 21 to 28 yr of the bicyclist who has now become the six-time consecutive Grand Champion of the Tour de France, at ages 27–32 yr. Maximal oxygen uptake (O2max) in the trained state remained at 6 l/min, lean body weight remained at 70 kg, and maximal heart rate declined from 207 to 200 beats/min. Blood lactate threshold was typical of competitive cyclists in that it occurred at 76–85% O2max, yet maximal blood lactate concentration was remarkably low in the trained state. It appears that an 8% improvement in muscular efficiency and thus power production when cycling at a given oxygen uptake (O2) is the characteristic that improved most as this athlete matured from ages 21 to 28 yr. It is noteworthy that at age 25 yr, this champion developed advanced cancer, requiring surgeries and chemotherapy. During the months leading up to each of his Tour de France victories, he reduced body weight and body fat by 4–7 kg (i.e., 7%). Therefore, over the 7-yr period, an improvement in muscular efficiency and reduced body fat contributed equally to a remarkable 18% improvement in his steady-state power per kilogram body weight when cycling at a given O2 (e.g., 5 l/min). It is hypothesized that the improved muscular efficiency probably reflects changes in muscle myosin type stimulated from years of training intensely for 3–6 h on most days.
Scientific considerations for physiological evaluations of elite athletes
To the Editor: Elite athletes are valuable study objects for exercise physiology: successful sportsmen offer unique insight into the extreme adaptation of the human organism to certain types of exercise and illustrate the amazing adaptation capacity of human physiology (9). Because of the unique characteristics of the study subjects, sample sizes in these investigations are usually low. Even case reports, such as in the article written by Dr. Coyle (1), can therefore be a valuable contribution to the scientific knowledge in this field.
Nevertheless, such studies should respect the basic principles of scientific investigations. We feel that the investigation presented by Dr. Coyle has serious limitations in this context.
Experimental design. The aim of the study was, according to the author, to report "the physiological changes that occur in an individual bicycle racer during a 7-yr period" and thereby illustrate "the extreme to which the human can adapt to endurance training." Unfortunately, the data presented in the manuscript do not contain enough physiological information of the athlete in question (Lance Armstrong) to draw a picture sufficient to illustrate his physiological profile and the associated adaptations over 7 yr: in fact, no testing was performed in immediate connection with his Tour de France wins. It can be assumed that his physiological performance at that moment was much higher than the ones measured and described by the manuscript. The performance data reported in the manuscript are common to many elite cyclists (4, 5), none of whom matches the wins of Armstrong. Furthermore, the exercise tests outside the cancer period date from the months of January, November, and September; these are periods where professional cyclists, who target peak form for races in July, have barely the same condition as during their peak season. Therefore, all speculations in the manuscript on potential data during his Tour de France wins are not supported by any of the presented test results. To display a complete physiological profile of the athlete and to draw the present conclusions, at least some data from peak season testing should have been included. Interestingly, no data from the years of best performance of the athlete are presented: during the period from 2000–2005, Armstrong won five consecutive Tours de France; unfortunately, no exercise test seems to have been conducted during that time, which is rather surprising for an athlete of Armstrong’s caliber.
Methods. To evaluate exercise performance and draw valid conclusions, it is essential to report data on the reliability and accuracy of the testing equipment, especially when only small changes are expected or the accuracy of the testing equipment is poor. In exercise physiology, especially the assessment of respiratory data is prone to errors linked to the testing procedure. This error, together with biological variation of maximal oxygen uptake, has been demonstrated to reach up to 5% (3,, thereby almost equaling the changes described in the manuscript. The same applies to the ergometry equipment: it has been demonstrated that many ergometers yield a high inaccuracy in their measurements, especially mechanically braked models, such as the one used for the present investigation (6, 10). In a comparable case report which uses the same type of mechanically braked ergometer (9), the authors included a 9% correction for their power measurements.
Unfortunately, the author does not report any data on the accuracy and reliability (such as calibration data) of his testing equipment. Especially when evaluating the calculations and conclusions drawn from the data, this would be of great help.
Furthermore, we are not aware of a reliable constant power mode in mechanically braked ergometers, such as the Monark model used for several tests in the present study.
Results and discussion. The author highlights the importance of improved muscular efficiency as being the main reason for Armstrong’s outstanding gain in performance. We feel that this assumption cannot be made on the basis of the presented information, because no records are available from periods where the athlete actually had peak form. In this context, Fig. 1 is not correct, because it implies that Armstrong’s gross and delta efficiency have been constantly rising since the age of 20 yr, despite a period of more than reduced physical condition during cancer treatment. On the basis of the presented data, the author cannot judge the efficiency of any other moment than the ones studied (November 1992, January 1993, August 1997, November 1999). Furthermore, the conclusion of the manuscript is even more surprising, because it has been shown that efficiency is not a key factor to differentiate between successful and unsuccessful cyclists (2, 7). Unpublished data from our laboratory support these assumptions: elite cyclists do not show higher efficiency than recreational cyclists. Furthermore, a high interindividual variability can be noted. In a longitudinal follow-up (intraindividually), however, efficiency remains remarkably stable, even when overall physiological exercise performance highly varies.
It is therefore more likely that, in addition to very favorable genetic assets of the athlete, common physiological adaptations associated with endurance training, such as an improved aerobic and possibly anaerobic energy metabolism, increased power-to-weight ratio, or enhanced recovery functions, might have added to the truly outstanding sporting achievements of Lance Armstrong.
It has to be considered that, aside from being determined by purely physiological factors, performance in sporting competitions is highly influenced by many other variables, such as tactical race understanding and motivational and psychological issues. Although speculative, the latter two might play a prominent role in Armstrong’s sporting achievements, especially when considering the athlete’s unique medical history and human experience as a cancer survivor. Armstrong might have gained the edge over his physiologically equally strong competitors by these means.
We feel obliged to raise these issues to the scientific community on behalf of all scientists working with elite athletes. Even when the popularity of an athlete might strongly influence the interest of publishing data, both from the author working with the athlete and the editor’s side, the basic principles for scientific investigations should be respected. Published data (especially if published in a highly regarded scientific journal like the Journal of Applied Physiology) represent the base of knowledge and interpretation for future investigations and should therefore fulfill these scientific principles to allow upcoming studies to rely on the validity of their outcomes.
REFERENCES
Coyle EF. Improved muscular efficiency displayed as Tour de France champion matures. J Appl Physiol 98: 2191–2196, 2005.[Abstract/Free Full Text]
Jeukendrup A, Martin DT, and Gore CJ. Are world-class cyclists really more efficient? Med Sci Sports Exerc 35: 1238–1241, 2003.[Medline]
Katch VL, Sady SS, and Freedson P. Biological variability in maximum aerobic power. Med Sci Sports Exerc 14: 21–25, 1982.[Medline]
Lee H, Martin DT, Anson JM, Grundy D, and Hahn AG. Physiological characteristics of successful mountain bikers and professional road cyclists. J Sports Sci 20: 1001–1008, 2002.[Medline]
Lucia A, Pardo J, Durantez A, Hoyos J, and Chicharro JL. Physiological differences between professional and elite road cyclists. Int J Sports Med 19: 342–348,1998.[ISI][Medline]
Maxwell BF, Withers RT, Ilsley AH, Wakim MJ, Woods GF, and Day L. Dynamic calibration of mechanically, air- and electromagnetically braked cycle ergometers. Eur J Appl Physiol 78: 346–352, 1998.[CrossRef]
Moseley L and Jeukendrup AE. The reliability of cycling efficiency. Med Sci Sports Exerc 33: 621–627, 2001.[Medline]
Myers J, Walsh D, Sullivan M, and Froelicher V. Effect of sampling on variability and plateau in oxygen uptake. J Appl Physiol 68: 404–410, 1990.[Abstract/Free Full Text]
Padilla S, Mujika I, Angulo F, and Goiriena JJ. Scientific approach to the 1-h cycling world record: a case study. J Appl Physiol 89: 1522–1527, 2000.[Abstract/Free Full Text]
Woods GF, Day L, Withers RT, Ilsley AH, and Maxwell BF. The dynamic calibration of cycle ergometers. Int J Sports Med 15: 168–171, 1994.[Medline]
REPLY
Edward F. Coyle
Department of Kinesiology and Health Education
The University of Texas at Austin
Austin, Texas 78712
To the Editor: I thank Dr. Schumacher et al. for the opportunity to discuss the reliability and validity of our methods. Regarding "scientific considerations," this study focused on physiology and not the science of bicycle racing. Our main purpose was not to make measurements around the Tour de France or to compare this subject (Lance Armstrong) with other champions. The fact that our subject happened to eventually win the Tour de France was interesting but not the main "scientific consideration." Changes in muscle efficiency with 7 yr of training was the focus.
Reliability was most important, both in terms of the subject as well as the measurements of indirect calorimetry and power. This subject’s level of training and accessibility were most reliable from year to year in the early part of the competitive season when most of our measures were made. Besides, our study of Armstrong began before he ever competed in the Tour de France. The fact that we did not report data after this subject won his first Tour de France emphasizes, again, that our purpose was to observe the maturation and not report the characteristics of the existing champion.
Schumacher et al. have requested data regarding the reliability of our respiratory testing equipment for measuring oxygen consumption. During submaximal exercise at 60–70% maximal oxygen consumption in a group of competitive cyclists (circa 1994), we have observed that oxygen consumption when measured on 8 separate days in a given individual displayed an average range of 0.08 l/min and a coefficient of variation of ±0.87% (2). See Martin et al. (5) for additional insight. The notion that a set 9% correction should be applied to all Monark ergometers is not supported by Maxwell et al. (6). The model 819 Monark ergometer used by Armstrong was calibrated statically and dynamically using pedal dynamometers and found valid to within ±3% (1, 4), and power can be held constant [as detailed in Martin et al. (5)].
Schumacher et al. state that "Fig. 1 is not correct" and then say that "on the basis of presented data, the author cannot judge the efficiency of any other moment than the ones studied (November 1992, January 1993, August 1997, November 1999)." The manuscript never "judged" or speculated about efficiency as it only reported actual data. Removing data from 1997 does not alter the line between 1992 and 1999. These data over years, to our knowledge, are the only published addressing long-term efficiency and training. These data seem to conflict with notions of Schumacher et al., because they state "efficiency is not a key factor to differentiate between successful and unsuccessful cyclists" on the basis of their own unpublished data as well as the work of others (7). We have presented a model of how numerous physiological factors interact to determine endurance performance and have discussed that efficiency by itself does not account for most of the interindividual variations in performance. In fact, in our 1991 manuscript (1), we also report that efficiency in a group of elite cyclists does not differ significantly from a group of good cyclists because of the high degree of individual variation in efficiency and fiber type. However, in a following study during which maximal oxygen consumption and lactate threshold were matched in a pairs of competitive cyclists, it was clear that performance power was significantly higher in subjects with greater gross efficiency and greater percentage of type I fibers (3). In fact, Armstrong makes this point in that his efficiency was only average when he was 21–22 yr despite the fact that he was already elite and world champion. However, his efficiency improved and he was able to generate 8% more power when cycling at a constant O2 of 5.0 l/min.
We appreciate that winning the Tour de France requires tactical race understanding and motivational and psychological issues, among other things. However, nonphysiological factors and the winning of the Tour de France, although interesting, are not the focus of this investigation.
REFERENCES
Coyle E, Feltner M, Kautz S, Hamilton M, Montain S, Baylor A, Abraham L, and Petrek G. Physiological and biomechanical factors associated with elite endurance cycling performance. Med Sci Sports Exerc 23: 93–107, 1991.[ISI][Medline]
Gonzalez-Alonso J. Dehydration and Cardiovascular Hemodynamics During Exercise (PhD thesis). Austin, TX: University of Texas, 1994, p. 203.
Horowitz J, Sidossis L, and Coyle E. High efficiency of type I muscle fibers improves performance. Int J Sports Med 15: 152–157, 1994.[ISI][Medline]
Kautz SAFM, Coyle EF, and Baylor AM. The pedaling technique of elite endurance cyclists: changes with increasing workload at constant cadence. Int J Sport Biomech 7: 29–53, 1991.
Martin DT, Quod MJ, and Gore CJ. Has Armstrong’s cycling efficiency improved? J Appl Physiol 99: 1628–1629, 2005.[Abstract/Free Full Text]
Maxwell B, Withers R, Ilsley A, Wakim M, Woods G, and Day L. Dynamic calibration of mechanically, air- and electromagnetically braked cycle ergometers. Eur J Appl Physiol 78: 346–352, 1998.[CrossRef]
Moseley L, Achten J, Martin J, and Jeukendrup A. No differences in cycling efficiency between world-class and recreational cyclists. Int J Sports Med 25: 374–379, 2004.[Medline]
PASSEZ A AUTRE CHOSE ET ARRETER DE PARLER ! ET EN JUILLET NE REGARDEZ PAS LA TELE ! 
t'es chiant turtle
