Lotta push back. These studies with placebo groups starting to accumulate now.
As I’ve said for over a decade, its not the altitude, the air, or red blood cells, its the hills that come with being in the mountains. You just need the hills [if you look around you can find some at sea level too], not the altitude, not the oxygen, and not the EPO………

“The aim was to investigate whether 6 weeks of normobaric “Live High-Train Low” using altitude tents affect highly trained athletes incremental peak power, 26-km time-trial cycling performance, 3-min all-out performance, and 30-s repeated sprint ability.”

“In a double-blinded, placebo-controlled cross-over design, seven highly trained triathletes were exposed to 6 weeks of normobaric hypoxia “Live High-Train Low” and normoxia (placebo) for 8hours/day.

“Live High-Train Low” exposure consisted of 2 weeks at 2500m, 2 weeks at 3000m, and 2 weeks at 3500m.”

“Incremental peak power output was similar after both interventions, placebo….Likewise, mean power output was similar between treatments as well as before and after each intervention for time trial, placebo, and 3-min all-out.”

“Furthermore, peak- and mean power output during repeated sprint exercise was similar between groups at all time points. In conclusion, 6 weeks of normobaric “Live High-Train Low” using altitude tents simulating altitudes of 2500–3500m conducted in a double-blinded, placebo-controlled cross-over design do not affect power output during an incremental test, a ~26-km time-trial test, or 3-min all-out exercise in highly trained triathletes. Furthermore, 30s of repeated sprint ability was unaltered.”

Large section with studies showing no efficacy for altitude training or EPO use…..TheETG background science info —– https://theetgtrackclub.com/documents/TheETGsportscibackgroundMasterOfSport.pdf