The performance areas scientifically proven (and supported by huge amounts of anecdotal evidence) to be improved by Altitude Training, include:

“Dedicated blocks of hypoxic training have played an integral role in our conditioning strategy. Players have made rapid gains in endurance following these blocks which has translated to improved performance in games.”
S&C coach at a leading Pro 12 Rugby club

A few examples that illustrate the typical improvements readily achievable by a properly constructed Simulated Altitude Training regime are:

Increasingly, simulated altitude plays a major role in returning players and athletes back to their respective disciplines in the shortest possible time.

“The Altitude Chamber is a key aspect of our rehabilitation platform. Because altitude produces an effective physiological stimulus at low workloads injured players can retain their fitness and are able to return to play sooner, once their injury has healed.”
Rebecca Toone PhD Intensive Rehab Physiologist EIS

A secondary aspect is that bodies that have trained hypoxically are more efficient at extracting oxygen from the air and delivering it to the various parts of the body. So, it follows that, should injury occur, an hypoxically trained system will deliver oxygen to the point of injury more effectively, thereby assisting the recovery process for the injury itself.