The fighters have weighed in for tomorrowâ€™s UFC 150 card at the Pepsi Center in Denver, Colorado, but the x-factor in each of the 10 fights is how the fighters will react to fighting at the Mile High Cityâ€™s infamous altitude.
Denver stands at 5280 feet (or 1609.344 meters) above sea level and the oxygen content is 17% less than UFC lightweight title challenger Frankie Edgarâ€™s hometown of Tomâ€™s River, NJ.
And unbeaten UFC heavyweight Travis Browne â€“ who fought in Denver at last yearâ€™s UFC 135 card - believes the UFC 150 athletes who chose not to get into town early could suffer in the Octagon.
Browne said:Â "The biggest thing that you have to get over when you fight there is that your body doesn't respond the same at the high altitude. You can't catch your breath and your body fails a lot quicker.
â€śI think Benson and Donald will have advantages in their fights because they've been training at high altitudes for their entire camps. It's not something that you can get used to in a short amount of time. You really have to spend a lot of time adjusting."
In the main event UFC lightweight champion Benson â€śSmoothâ€ť Henderson and former UFC lightweight titleholder Frankie â€śThe Answerâ€ť Edgar rematch to decide who is the best lightweight on Earth.
â€śI know what this air can do to your lungs,â€ť said champion Henderson. â€śIâ€™m from Colorado Springs, and you have to take this seriously. Iâ€™ve been here for three weeks already. You can feel it when you run, or spar.
â€śYour body gives out earlier, you canâ€™t recover as fast. I grew up here, and you can get used to it, but that doesnâ€™t happen in a week or two weeks. Thatâ€™s why Iâ€™ve been here for a while now.â€ť
Likewise, in the co-main event, local fighter Donald â€śCowboyâ€ť Cerrone arrived in Colorado as soon as the fight withÂ Melvin â€śThe Young Assassinâ€ť Guillard was signed, in order to get his lungs used to the rarified air of the Mile High City.
He explained: â€śI grew up in Colorado Springs and my family and friends are all from Denver and I got here a month ago. It takes that long to be able to push yourself at this altitude.â€ť
Â Here are the weigh-in results
MAIN CARD (Pay-per-view, 10 pm ET/7pm PT)
UFC Lightweight Champion Benson Henderson 154.4lbs vs. Frankie Edgar 154.6lbs
Lightweight Donald Cerrone 155lbs vs. Melvin Guillard 157.5lbs
Welterweight: Jake Shields 185lbs vs. Ed Herman 185lbs
Middleweight: Yushin Okami 185lbs vs. Buddy Roberts 184lbs
Featherweight: Justin Lawrence: 145lbs vs. Max Holloway 145lbs
PRELIMINARY CARD (FX, 8pm ET/5pm PT)
Featherweight: Dennis Bermudez 145lbs vs. Tommy Hayden 144lbs
Middleweight: Jared Hamman 184lbs vs. Michael Kuiper 185lbs
Bantamweight: Ken Stone 135lbs vs. Erik Perez 135lbs
Bantamweight Dustin Pague 136lbs vs. Chico Camus 135lbs
Featherweight: Nik Lentz 145lbs vs. Eiji Mitsuoka 145lbs