131 challengers have signed up for the Nike Women's Marathon in San Francisco, so sign up to join in on this impressive run through the city. With the Race Day Challenge, Nike is providing the chance to win the marathon just for syncing your run! Race Day is October 25th, but registered participants who run with Nike+ and sync their race run between October 17-24 will be entered to win a weekend for two at the 2011 Nike Women's Marathon.

Invite your friends on Facebook and Twitter, and get into your training regimen now. Charge up your iPod and turn on your Nike SportBand, because you don't have to be the fastest to win this challenge.

See more details on the Nike Women's Marathon here.