Gloves and hats are in high demand as runners prepare for near freezing temperatures at the starting line.
There's nothing like running 26.2 miles to warm you up. Race organizers are preparing for the course to be littered with left-over clothing as runners shed their layers.
"The last few years we have seen the cascade of clothes coming off. We capture all those garmets and they go to local charity. That's a great piece of our event," said Carey Pinkowski, Chicago Marathon Executive Director.
"These conditions have been essentially the same for a few weeks so runners have been able to acclimate to conditions well," said Dr. George Chiampas, Chicago Marathon Medical Director.
There are as many reasons for running as there are participants. One group of vets will be making a statement with each step. Sergio Lopez of Joliet lost both of his legs to a roadside bomb in Iraq three years ago.
"Just to prove to myself I can still be athletic and be as outgoing as I used to be way back when," said Spec. Sergio Lopez, U.S. Army (Retired).
Molly Akers uses the marathon to mark her fifth year cancer-free.
"It symbolizes that you can go through anything. You grit your teeth through hard times and you find yourself looking back and thinking 'I'm a lot different that I thought," said Molly Akers, a marathon runner from New Lenox.
This event draws elite athletes from all over the world. This year there's a runner each from Burundi and Uzbekistan. But 40-percent of those who will run out here will be competing in their first marathon.
The marathon kicks off Sunday at 7:30 a.m.
Several streets will be closed for the marathon. For more information on the closures, visit www.chicagomarathon.com.