...le but de la discussion n'est pas de se fermer sur une idée et de ne plus en démordre, mais bien de comprendre un peu la physio et l'altitude. J'essaie de raisonner de façon scientifique et d'apporter une pierre à l'édifice. Après, j'en tape, je ne veux pas bouffer mon temps sur une thématique de recherche qui n'est pas la mienne... La mienne justement me prend déja pas mal de temps...
Si on reprend de façon a peine plus approfondi les deux réf que tu cites, je pense que ce ne sont pas forcément les plus pertinentes sur la question :
La première (date de 1999)
http://www.ncbi.nlm.nih.gov/entrez/quer ... s=10589872
Med Sci Sports Exerc. 1999 Nov;31(11):1665-76.
Comparing cycling world hour records, 1967-1996: modeling with empirical data.
Bassett DR Jr, Kyle CR, Passfield L, Broker JP, Burke ER.
Exercise Science Unit, University of Tennessee, Knoxville, USA.
PURPOSE: The world hour record in cycling has increased dramatically in recent years. The present study was designed to compare the performances of former/current record holders, after adjusting for differences in aerodynamic equipment and altitude. Additionally, we sought to determine the ideal elevation for future hour record attempts. METHODS: The first step was constructing a mathematical model to predict power requirements of track cycling. The model was based on empirical data from wind-tunnel tests, the relationship of body size to frontal surface area, and field power measurements using a crank dynamometer (SRM). The model agreed reasonably well with actual measurements of power output on elite cyclists. Subsequently, the effects of altitude on maximal aerobic power were estimated from published research studies of elite athletes. This information was combined with the power requirement equation to predict what each cyclist's power output would have been at sea level. This allowed us to estimate the distance that each rider could have covered using state-of-the-art equipment at sea level. According to these calculations, when racing under equivalent conditions, Rominger would be first, Boardman second, Merckx third, and Indurain fourth. In addition, about 60% of the increase in hour record distances since Bracke's record (1967) have come from advances in technology and 40% from physiological improvements. RESULTS AND CONCLUSIONS: To break the current world hour record, field measurements and the model indicate that a cyclist would have to deliver over 440 W for 1 h at sea level, or correspondingly less at altitude. The optimal elevation for future hour record attempts is predicted to be about 2500 m for acclimatized riders and 2000 m for unacclimatized riders.
PMID: 10589872 [PubMed - indexed for MEDLINE]
le second article qui date de 1989 quand même (les méthodes ont évolués en 20 ans):
http://www.ncbi.nlm.nih.gov/entrez/quer ... ds=2736448
Can J Sport Sci. 1989 Jun;14(2):93-8.
[A comparison of cyclists' time records according to altitude and materials used]
[Article in French]
Peronnet F, Bouissou P, Perrault H, Ricci J.
Departement d'education physique Universite de Montreal, Quebec.
The purpose of this study was to re-assess the energy cost of track cycling in order (a) to compare the one-hour world records at sea-level and altitude with classical bicycles or with modern bicycles including aerodynamic components, and (b) to estimate the optimal altitude to set a new one-hour world record. Energy cost of track cycling with a classical or aerodynamic bicycle was estimated according to the equation developed by di Prampero et al. (1979) using data from Davies (1980) for the rolling resistance coefficient and from Gross et al. (1983) for the aerodynamic resistance coefficient for each type of bicycle. When compared to the classical track-bicycle, and to the bicycle studied by di Prampero et al. (1979), the aerodynamic track-bicycle reduces the resistance coefficient by 11.7 and 16.9% respectively. According to these estimations the cyclists sustain 87-95% of maximal aerobic power over one hour, which is a likely value for a 60 min exercise period for top-level athletes. When the reduction of air density and of maximal aerobic power with altitude are taken into account, equivalences between performances achieved at different altitudes and with the two types of track-bicycles, can be computed. The best overall performance appears to be the current one-hour record at sea-level using an aerodynamic bicycle (Moser: 50.644 km.h-1). This performance is equivalent to 53.5 km.h-1 in Mexico City (2230 m), 54.4 km.h-1 in La Paz (3417 m) and 54.5 km.h-1 at 3843 m (472 mmHg), which would be the optimal altitude to set the record.
PMID: 2736448 [PubMed - indexed for MEDLINE]
[...]Et puis les auteurs en questions sont parmi les physiologistes du sport les plus reputes[...]
je ne doute absolument pas leur compéétence en physio du sport, et je n'ai même pas la prétention de leur arriver à la moitié de cheville, mais si tu fais le pubmed "performance et altitude" de ces deux équipes, tu trouves : deux papiers pour le premier et 1 papier pour l'équipe de Ricci.
En revanche, j'ai trouvé ça qui est plus récent et peut nous intéresser :
http://www.ncbi.nlm.nih.gov/entrez/quer ... &DB=pubmed
(taper : altitude and sport)
http://www.ncbi.nlm.nih.gov/entrez/quer ... &DB=pubmed
(taper altitude and performance)
Clin Lab Haematol. 2004 Dec;26(6):373-7.
Behaviour of haematological parameters in athletes performing marathons and ultramarathons in altitude ('skyrunners').
Banfi G, Roi GS, Dolci A, Susta D.
Direzione Sanitaria, Istituto Ortopedico Galeazzi, Milano, Italy.
giuseppebanfi@supereva.it
We observed athletes performing marathons and ultramarathons in altitude over several years to study the behaviour of haematological parameters in order to screen eventual paraphysiological or pathological conditions (sports anaemia). We collected samples from 124 athletes participating in seven races; 23 athletes were recruited in different races: 16 for four times, four for three times, and three for two times. The pre- and post-race values of erythrocytes, haemoglobin and packed cell volume did not show statistically significant differences in the studied athletes. The erythrocytes' indices (MCV, MCH, MCHC) and red cell distribution width (RDW) also were not significantly modified by the strenuous effort. The leukocytes were significantly increased because of immunological involvement during the endurance performance. Platelets and relative indices were not significantly modified. The stability of packed cell volume and haemoglobin in athletes performing training and races in altitude is strong evidence for the use of these parameters as an index of general health status and for illustrating possible abnormal increase because of exogenous stimulation of bone marrow. The preanalytical and analytical accuracy is crucial to assure clinical validity of the collected data: we strictly observed international recommendations in this field.
PMID: 15595993 [PubMed - in process]
Scand J Med Sci Sports. 2004 Oct;14(5):303-10.
Training and performance characteristics among Norwegian international rowers 1970-2001.
Fiskerstrand A, Seiler KS.
Norwegian Rowing Federation, Oslo, Norway.
This study quantified changes in training volume, organization, and physical capacity among Norwegian rowers winning international medals between 1970 and 2001. Twenty-eight athletes were identified (27 alive). Results of physiological testing and performance history were available for all athletes. Twenty-one of 27 athletes responded to a detailed questionnaire regarding their training during their internationally competitive years. Maximal oxygen uptake (VO2 max) increased 12% (6.5+/- 0.4 vs. 5.8+/-0.2 L min(-1)) from the 1970s to the 1990s. Similarly, 6-min ergometer rowing performance increased almost 10%. Three major changes in training characteristics were identified: (1) training at a low blood lactate (< 2 mM) increased from 30 to 50 h month(-1) and race pace and supra-maximal intensity training (approximately 8-14 mM lactate) decreased from 23 to approximately 7 h month(-1); (2) training volume increased by approximately 20%, from 924 to 1128 h yr(-1); (3) altitude training was used as a pre-competition peaking strategy, but it is now integrated into the winter preparation program as periodic 2-3-week altitude camps. The training organization trends are consistent with data collected on athletes from other sports, suggesting a "polarized" pattern of training organization where a high volume of low intensity training is balanced against regular application of training bouts utilizing 90%-95% of VO2 max.
PMID: 15387804 [PubMed - in process]
Scand J Med Sci Sports. 2005 Feb;15(1):48-57.
Training response of adolescent Kenyan town and village boys to endurance running.
Larsen HB, Nolan T, Borch C, Sondergaard H.
The Copenhagen Muscle Research Centre, Rigshospitalet and University of Copenhagen, Denmark.
To investigate the response to endurance training on physiological characteristics, 10 Nandi town boys and 14 Nandi village boys 16.5 and 16.6 years of age, respectively, from western Kenya performed 12 weeks of running training. The study was performed at altitude ( approximately 2000 m.a.s.l. approximately 595 mm Hg). Training heart rate and speed were registered during every training session throughout the entire training period. While town and village boys trained at similar heart rates (172.1 vs. 172.5 beats min(-1)), the training speed of the town boys was 9% lower compared with the village boys (12.4 vs. 13.6 km h(-1), P<0.001). Significant increases in VO(2max) were observed in the town boys (from 50.3 to 55.6 mL kg(-1) min(-1), P<0.001) and in village boys (from 56.0 to 59.1 mL kg(-1) min(-1), P<0.002). Significant decreases in submaximal heart rate (from 172.4 to 160.3 beats min(-1) (P<0.005)), blood lactate (from 2.7 to 1.4 mmol L(-1) (P<0.005)) and ammonia concentration (from 102.0 to 71.4 mumol L(-1) (P<0.01)) at 9.9 km h(-1) were observed in the town boys, while similar decreases in heart rate (from 170.2 to 159.2 beats min(-1) (P<0.001)), blood lactate (from 2.4 to 1.4 mmol L(-1) (P<0.001)) and ammonia concentration (from 102.5 to 72.7 lmol L(-1) (P<0.001)) at 10.9 km h(-1) were observed in the village boys. The oxygen cost of running was decreased from 221.5 to 211.5 mL kg(-1) km(-1) (P<0.03) in the town boys and from 220.1 to 207.2 mL kg(-1) km(-1) (P<0.01) in the village boys. The 5000 m performance time of the town boys was significantly greater than that of the village boys (20.25 vs. 18.42 min (P=0.01)). It is concluded that no difference was observed in trainability with respect to VO(2max), running economy, submaximal heart rate, and submaximal blood lactate and ammonia concentration between Kenyan Nandi town and village boys. The higher performance level of the village boys was likely due to a higher VO(2max) of these boys.
PMID: 15679572 [PubMed - in process]
Int J Sports Med. 2004 Nov;25( 8 ):561-8.
Hemoglobin mass and peak oxygen uptake in untrained and trained female altitude residents.
Boning D, Cristancho E, Serrato M, Reyes O, Mora M, Coy L, Rojas J.
Institute of Sports Medicine; Charite - University Medicine Berlin, Berlin, Germany.
dieter.boening@charite.de
Total hemoglobin mass has not been systematically investigated in females at altitude. We measured this quantity (CO-rebreathing method) as well as peak oxygen uptake in 54 young women (age 22.5 +/- 0.6 SE years) with differing physical fitness living in Bogota (2600 m) and compared the results with those of 19 subjects from 964 m in Colombia and 75 subjects from 35 m in Germany. In spite of an increased hemoglobin concentration the hemoglobin mass was not changed in highlanders (means 9.0 to 9.5 g . kg (-1) in untrained subjects at all altitude levels). Endurance trained athletes, however, showed a rise in hemoglobin mass by 2 - 3 g . kg (-1) at all sites. Erythropoietin was little increased in Bogota; iron stores were within the normal range. Aerobic performance capacity was lower at high altitude than at sea level and remained so also after correction for the hypoxic deterioration in untrained and moderately trained subjects but not in athletes; possibly the cause was reduced daily physical activity in non-athletic Bogotanians compared to lowlanders. After exclusion of the factor V.O(2peak) by analysis of covariance a mean rise of 6.6 % in hemoglobin mass at 2600 m was calculated being smaller than in males (> 12 %). The attenuated increase of hemoglobin mass in female highlanders possibly results from stimulation of ventilation improving arterial oxygen saturation or from an increased hypoxia tolerance of cellular metabolism both caused by female sexual hormones.
PMID: 15531997 [PubMed - in process]
REMARQUE 1 : j'ai rien vu d'évident à moins de 2000 m d'altitude (j'ai pas non plus fouillé, a fond...). Si t'as les ref des publi décrvant ce que tu cite plus haut (500m, 1000m, 1500m...) ça m'intéresse vraiment de les lire. (Pour la mise en place de stages en moyenne altitude par exemple......)
REMARQUE 2 : les études rétrospectives sur les sportifs de haut niveau et notamment les cyclistes, faut m'excuser, mais elles restent très discutables. Quand t'as des données métaboliques, biologique..."suréalistes" de certains organismes bien imprégnés, tu vas pas en conclure grand chose, et tout est possible.
Je suis désolé, mais avec les PMA, VO2M des Indurains, et même Moser, Boardman, Amstrong... je pense qu'ils peuvent encore pédaler à 8000 m en développant 450 watt, et on pourrait même voir une ammélioration par rapport à 1000m d'altitude !!!!
... donc méfiance !
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%] and women [-3.8 (1.2)%]. Arterial oxyhaemoglobin saturation (SaO2) at VO2peak was significantly lower at MH compared with N in both men [90.1 (0.6)% versus 92.0 (0.6)%] and women [89.7 (3.1)% versus 92.1 (3.0)%]. While SaO2 at VO2peak was not different between men and women, it was concluded that relative, rather than absolute. VO2peak may be a more appropriate predictor of exercise-induced hypoxaemia. For men and women, it was calculated that 67-76% of the decrease in VO2peak could be accounted for by a decrease in O2 delivery, which indicates that reduced O2 tension at mild altitude (580 m) leads to impairment of exercise performance in a maximal work bout lasting approximately 5 min.
