Holding their breath for hours on end

[Tavrobel]

How do they do it? Why can only some people do it?

Because they are athletes, it's their job, they've trained from childhood to do it, or otherwise in excellent physical shape? It isn't unheard of for people to hold their breaths for a very long time; it's only slightly more of a stretch for people to learn how to hold their breaths while exerting themselves in other ways.

Spira brains might have greater tolerance for oxygen deprivation. It could make sense as an evolutionary adaptation.

Alternatively, blame it on pyreflies. They do everything.

Unless that wouldn't count as machea.

It is, but it doesn't count, because it's entertainment (explicit statement through in-game lore). Generally, Sin responds to weaponized machina. Incidentally, it helps Yevon keep the general population down by distracting them from the prospect of a very violent death, sometime before the 11 o'clock news.

The play periods in Blitzball are only a few minutes aren't they?

5 total, 2:30 with a halftime. I don't believe that there are any pauses or timeouts.

Then again, the version of Blitzball we are playing as a minigame in FFX could be an abridged version, in the same way that Madden shortens most football games down to 5 minute quarters, instead of 15 minute quarters. For comparison, most NFL games are 60 minutes long, but most actually take 3 hours, with 10 commercial breaks per half mandated by the NFL agreement with its broadcasters and advertisers. Playing a full version of Blitzball may have similar issues.