Pride 10 minute round - most demanding sport?

Spike has been showing some of the old Pride MMA fights. They have one 10 minute round, followed by 2 - 5 minute rounds.

We have had debates in the past over what is the most difficult or most demanding athletic activity. But I find myself unable to come up with anything that requires as high a level of athletic activity and intellectual involvement for as long a period as that 10 minute first round. The fighter has no teamates to help him out should he falter momentarily, and the briefest misstep or lapse in concentration could result - not in the opponent scoring a point, but in an immediate loss.

(Having done (very little) boxing, BJJ, and MMA in the past, I cannot imagine what it would be like to fight for 10 continuous minutes!)

A couple of things that come to mind are running a marathon, or the Tour de France. But it seems that even in those there is some ability to “coast” at least for brief periods. If you lose ground, you might be able to make it back up. And in the Tour, other than in time trials, you have teamates to work with.

So, what are your suggestions for the most demanding athletic activity?

Most demanding athletic activity IMO would be something like Ultraman - but this is probably tougher mentally (although not easy physically).

Something like Badwater maybe - YMMV

all respect to triathletes… never done it before so this is simply my opinion from what i have done…

mma bjj sparring for five minutes is simply exhausting… 10 minute pride rounds are sick sick sick… three min and a half my mouth is wide open… u could fit one of dagwood sandwiches in their… i respect mma fighters because climbing into the cage takes a certain something… climbing Back in after gettin whooped takes more… and simply having the gas tank to get thru it… and THINK while its goin on…

Biking time trials, or erg/rowing racing, are essentially sprints for as long as you can possibly keep it up. They’re not all out sprints, as you have to be able to keep it up for 20-30 minutes but those guys and gals are pushing harder than I care to imagine for the entire time, no coasting. It’s scary how far they can push their bodies.

Granted, no one is trying to kick your head during those activities…

Steroids were legal in Pride.