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More on Altitude & Hypoxia

03 Nov 2006

Even though athletes have been successfully utilizing altitude training methods, there is no unanimous consent between researchers worldwide over the benefits on sport performance. 
The results of the studies have almost always been evaluated with statistical examinations of the behavior of a single group of athletes. 

B.D. Levine et al. (J.Appl.Physiol. 1998;85:1448-1456) were the first to clearly identify two classes of athletes, RESPONDERS and NON RESPONDERS to altitude training. 
The Authors verified the following different characteristics of behavior: 

- RESPONDERS athletes manifest a major EPO production and an increase in red blood cells volume (RCV) by 8% after 4 weeks at altitude 

- NON RESPONDERS athletes have a less evident and enduring increase in EPO, and lack an increase RCV. 

Both groups show a similar rise in Hb concentration (+8%), but for NON RESPONDERS this is due to a decrease in plasma volume (-8%) and not to a real increase in the total amount of Hb. 

Therefore the concentration of Hb is not a reliable marker to evaluate whether there was an effective erythropoietic stimulation: it is necessary to measure the total amount of Hb. 

In Levine’s study, RESPONDERS are able to increase VO2max by 6.4% and the speed in a simulated race (5000m) by 3.7%, while NON RESPONDERS did not show any improvement. 

D.Boning et Al. (Int.J.sports Med 2001; 22:572-578) demonstrated that athletes residing in Bogotà (2500m above sea level) have a concentration of EPO (33.3U/l) and reticulocytes (2.4%) superior to non-athletes living in Bogotà (EPO = 19.4U/l ; reticulocytes = 1.5%), while having a concentration of Hb visibly inferior: 16.0 g/dl versus 17.4 g/dl respectively. 
The total amount of Hb is also decisively higher for athletes: 14.7g/kg compared to the lower 13.1 g/kg of non-athletes. 

Training at altitude is therefore a further stimulus in EPO and Hb production; even at sea level, training is effective for such production, and this is particularly true for cyclists who often train and race on mountains even without sojourning at altitude. 

Recently several researchers pointed out the phenomenon of neocytolysis as means of self-regulation of RCV (Ann.Intern.Med. 2001;134:652-656). 
Just like astronauts coming back from space, residents at altitude coming down to sea level show a significant destruction of young red blood cells (neocytes) with a consequent reduction in RCV and increase in ferritin, bilirubin and LDH. 
The Authors verified that neocytolysis is nullified by the administration of small doses of EPO, therefore a well trained athlete, who produces more EPO in comparison with a non-athlete, probably does not manifest any noticeable neocytolysis at the return from an altitude sojourn. 

In the last few years, the use of altitude simulators (hypobaric and normobaric hypoxia) caught the attention of athletes, specialists and researchers. 
Commercial and scientific interests have been crossing and intertwining, proposing dozens of articles and publications on the topic. 
In such information jungle it is often difficult to understand whether such instruments are useful to athletes and how to utilize them. 

A continuous hypoxic stimulation (10 days at 2800m in hypobaric chamber) is surely effective in EPO and red blood cells production. 
Even just sleeping at 2600-3000m of altitude for 11-23 nights increases EPO by 59%, reticulocytes by 30% and VO2max by 2% (J.Sports Sci. 2001;19:831-837). 

Three hours every day, 5 days a week, for 4 weeks at a simulated altitude of 4000m and 5500m provoke increases in EPO concentration by 100% and 400% respectively (Haematologica 2005 ;90:126-127). 

Two hours a day at 3800m for 5-12 days are capable of an increase in reticulocytes, as well as 90 minutes at 4000-5500m (Eur.J.Appl.Physiol. 2000;82:170-177). 

Intermittent hypoxic protocols instead seem less effective: 5' : 5' hypoxia - normoxia for a total of 70 minutes, 5 times a week , for 4 weeks does not have any effect on erythropoiesis and performance (J.Appl. Physiol. 2004;96:1800-1807) 

Training sessions at simulated altitudes in hypobaric chambers seem to increase VO2max and performance both at sea level (+11%) and at altitude (+19%) in comparison with a control group doing the same work load at sea level (Eur.J.Appl.Physiol. 1988;57:203-209).

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