Reviewers' Comments
Baker, A., & Hopkins, W.G. (1998). Altitude training for sea-level competition In: Sportscience Training & Technology. Internet Society for Sport Science. 

Although popular with coaches and athletes, altitude training for sea level competition remains a controversial issue amongst sport scientists. The changes in oxygen transport are attractive physiologically and make intuitive sense, but the scientific support for altitude training is not as clear as one would expect.

This comprehensive review concludes that the average improvement in performance in athletes who live high and train low is approximately 2 -3 %. This improvement, which is marginally greater than the 1-2 % variation in performance between tests, would still be important were it not for the lack of predictability in the response to altitude exposure. More work is necessary to identify the athletes who will benefit from these camps and, equally important, identify those individuals who should avoid altitude exposure. The hypoxic and hypercapnic drives to breathing would appear to warrant further attention as possible predictors of responders and non-responders. 

This paper provides a good summary of the available literature concerning the practice of "living high, training low". However, it should be noted that very little information exists on the response of truly outstanding endurance athletes to the procedure. As I understand it, the cited "in press" study of Chapman et al. (1998) with elite runners did not include a control group. I do not believe that the effectiveness of "living high, training low" has yet been unequivocally demonstrated with elite athletic populations.

A question can be raised as to whether the hematological effect of altitude really can be expected to last for the average lifetime of a red blood cell (i.e., 70-120 days). An increased rate of red blood cell destruction may well occur on return from altitude, resulting in comparatively rapid restoration of normal hemoglobin mass.

The authors indicate that an altitude of 2500 m can be simulated by reducing the ambient oxygen concentration from 21% to 15%. This is true only for sea level barometric pressure. It is important for readers to understand that ambient barometric pressure must be taken into account in determining the oxygen concentration required to simulate a particular altitude.

It is argued that paper performance gains with altitude exposure may be greater than those resulting from erythropoietin injections or "blood doping". This seems inconsistent with the fact that most studies of the latter techniques have found them to be highly effective, whereas the findings with altitude are more equivocal.

Overall, the paper represents an excellent contribution to the literature on athletes and altitude. The provision of practical guidelines derived from logical extrapolation of research findings is a special feature.

This article was months in the making with numerous revisions.  I originally approached Arnie to write an article on hypobaric chambers and Will suggested co-authoring to add altitude training issues.  Arnie's original draft included a set of initial studies that set the framework from which the article expanded to its current comprehensive form.  Will expanded the research analysis, coverage and discussion.  Arnie was to view the final version of the article at the time of publication for his approval to be listed as an author; however, he was out of town and not able to return my communications.  Thus, because of his initial input and feedback, I have credited co-authorship to Arnie.  Mary Ann Wallace