Friday afternoon the participants in UFC 129 will weigh in for Saturday night's fight.
In between something remarkable will happen, as combatants will move up an entire weight class or maybe even two in just over 24 hours.
The reason is that the fighters who step on the scale this afternoon are literally a shadow of their real selves.
Perhaps only jockeys, gymnasts, bodybuilders and supermodels put their bodies through such a rigourous process of self-denial.
The goal is to make weight and to do it they deny themselves food and fluids over a period of time in order get down to the limit of prescribed by their weight class. For a fighter like Georges St-Pierre, who would normally weigh about 190 pounds, it means getting to 170 pounds. It is a difficult process considering it's not like a highly conditioned athlete has a lot of weight to lose. But the more aggressive someone can be cutting weight - especially in a combat sport - the bigger the presumed advantage. A bigger fighter with longer reach and simply more mass should have some edge on a smaller opponent.
It doesn't sound like fun though, and carries with it significant risks both to a fighter's short-term health - there are several cases of high school and college wrestlers dying as a result of too rapid and too aggressive starvation and dehydration regimens in a rush to make weight.
Among professionals the trick is to go through the cutting process and still be at their competitive peak, mentally and physically, come fight night:
For almost every MMA fighter, from scrubs to superstars, cutting weight is just part of life, even if fans rarely get a glimpse of what goes into it. For men who want to be as light as possible on Friday afternoon and as big and strong as possible on Saturday night, making weight isn't as simple as showing up and stripping down to their underwear. Doing it the wrong way can hamper their abilities on fight night. Even doing it the right way can be tough on the mind and body, all at a time when fighters need both to be at their best.
According to a recent study at Cal State Fullerton (courtesy of Maggie Hendricks at Yahoo! Sports), cutting weight is even more likely to affect a fighter's mental state than his physical one. In a study published in the Journal of Strength and Conditioning Research, wrestlers who lost more than four percent of their body mass before a match showed "significantly higher levels of confusion on the day of the competition," even though the weight loss had no adverse effects on strength.
However, that doesn't take into account the stress it puts fighters under in the days leading up to the weigh-in, when they should be concentrating on the fight itself.
"It sucks just as much every time," said UFC light heavyweight Phil Davis. "But once you have it in your mind that you're going to make weight, you just have to have the mental fortitude to make it through."
As an NCAA national champion wrestler at Penn State, Davis was familiar with the torture of cutting weight well before he became an MMA fighter. Back in his college days, Davis said, it was a different challenge. He was weighing in twice a week for thirteen weeks, and couldn't afford to get too far over the weight limit.
"Now I'm doing it once every two or three months, so I can afford to be a little looser with it. When I was wrestling in college I couldn't afford to lose twenty pounds all in one day, then wrestle that night and do it all again the next day."
Amid reports that Georges St-Pierre's weight will fluctuate from 170 pounds this afternoon to 190 or more by the time he takes the stage at Rogers Centre, it will be interesting to see if he's got the process just right or not.