[semicolon_storm]

It seems unlikely, athletes are consuming liters of oxygen per minute. Plus, the impact is at least partially offset by needing to carry the extra weight with you.

Different story for apnea sports like freediving where a little bit of extra oxygen goes a long way.

[o11c]

A liter of liquid is a lot more than a liter of gas ...

[Liftyee]

Isn't liquid oxygen cryogenic (boils at -183C)? The engineering of keeping that ...there... gets interesting fast, especially when dealing with all the cold (absorbed heat from expanding gas) and containing the pressure while also releasing oxygen slowly.