A temporary performance boost for which you then pay the toll? This is definitely not the case. Altitudream.com has had a huge number of athletes in recent years using one altitude tent brought to better performance.
Athletes have never reported to us any negative effects of the height tent that may or may not have been expressed in the longer term. On the contrary, the improved oxygen efficiency of the body also appears to remain present in the longer term. For example, many athletes indicated that long after their blood levels returned to normal, they still noticed that their 'smoother' breathing had remained.