Last Sunday, at 4:38 a.m., I woke up on an air mattress on the floor of my friend's Wicker Park apartment. After 20 minutes of hurried preparation and eating, I sprinted out the door with my friend and the boyfriend in tow.

At 6:40 a.m., we boarded a school bus with 20 other groggy, unshaved, and un-showered comrades, heading off to God-knows-where. (This turned out to be the Hyde Park area, near the Museum of Science and Industry.)

At 7:10 a.m., I battled the longest port-o-potty line of my life, only to be rewarded with the foul stench of nervous pre-race bowl movements.

At 7:50 a.m., the start gun went off, and I resigned myself to 13.1 miles, or approximately two hours, of physical discomfort and mental duress.

At 9:58 a.m., in the midst of 13,531 other people, I triumphantly crossed the finish line of the Chicago Half Marathon.

At 10:00 a.m., I munched on a cookie and thought to myself, "Oh shit. I'm doing twice that distance in exactly one month."

The Chicago Half Marathon fell exactly four weeks from the Chicago [Full] Marathon, which will take place on October 11, 2009. On that fateful day, 45,000 people, myself and the boyfriend included, will cover 26.2 miles of Chicago's streets on foot. Determination and endurance will be tested, personal records will be set, and I will probably lose my mind as my body decides to eat itself between Miles 20 and 26.2. (This gruesome phenomenon is known as "lean muscle cannibalization.")

Sunday's race, a feat in and of itself, was actually a test to gauge where I stand in my marathon training. All summer, I have been waking up at Dark O'Clock, lacing up my shoes, and running all over Champaign AND Urbana (and sometimes Savoy). One of my right toenails is turning purple, I have a comical farmer's tan on my legs, and my laughable excuse for a Saturday night social life has all but disappeared in preparation for running long on Sundays.

And if I have learned one thing through these past three months of willpower and dedication, it is this: never underestimate the sheer and awesome power of personal vanity.

After spending the first 18 years of my life as a sedentary nerd with a penchant for tortilla chips, I started running in college out of shame and peer pressure. My undergraduate institution is consistently voted "Hottest for Fitness", as the sinewy arms and rippling muscles of the student body will attest. Not wanting to be left out of Collegiate Fit Club, I asked my mom for a pair of real running shoes and found a very simple training program with the eventual goal of being able to run six miles over the course of an hour. The first day of the program was "Run for 30 seconds. Walk for four minutes and 30 seconds. Repeat seven times."

Five years later, I am proud to say that the same vanity still motivates me to run faster times and longer distances. To be fair, I have learned to view running as something more than simply an efficient way to create a caloric deficit; I now enjoy the challenge of running all by itself. (And I could say something else like "I love the crunch of fall leaves underfoot on a morning run," but that's just too cliché.)

Running has many benefits, both physical and otherwise. Besides the obvious perks of burning all those calories, running can strengthen your bones and joints, decrease your risk of a heart attack, and certainly increase your cardiovascular endurance. In addition, running brings with a new social outlet, filled with both support and friendly competition. Most mornings, I wheeze and pant through some of my best conversations with my running buddy, on topics ranging from the effectiveness of spermicidal condoms to the precise definition of a hipster.

Finally, running allows you to eat... a lot. I would be a bold-faced liar if I said I wasn't excited every Sunday when I get to eat copious amounts of bread, peanut butter, potatoes, and ice cream to refuel from my long run.

But perhaps most importantly, running can be one of the best ego boosters around. To be quite honest: I oftentimes still run out of vanity. I love the satisfaction of knowing that no matter how slow I run, I am still faster than someone sitting on the couch, eating chips. I might not look like a Nike sportswear model, but I am extremely proud of my muscular legs that will carry me 20 miles without protesting too much. And hopefully, when I cross (or drag myself) over the finish line in Chicago, I will congratulate myself on having entered the elite ranks of marathoners.

Remind me of all this at Mile 25.