What range do researchers actually agree on?
Across more recent meta-analyses, the consistent finding is that altitude blocks of roughly three weeks, at elevations between about 2,000 and 2,500 meters, are associated with measurable improvements in aerobic capacity markers, including hemoglobin mass and VO2max. That is a narrower and more specific claim than the loose idea that altitude simply helps, and it is the reason the elevation of both Iten and Addis Ababa's main training areas fall so squarely inside that window rather than significantly above or below it, where research shows the returns either flatten out or come with added recovery costs.
