What does everyone want to do before running a marathon? Well,  naturally, run another marathon. San Francisco never ceases to amaze me. Already teeming with sporty types of all varieties—surfers, skiers, rock climbers—cityslickers aren't content with just casually enjoying their activities, they're hungrily searching for the next challenge in a game of one-upmanship that apparently has no end.

So, for all you hard-core people out there, here's your next adventure. The day before this weekend's SF Marathon, you can run another 26.2 miles with ultramarathoner Dean Karnazes. Many of you may already know Dean—we profiled him in last year's Best Of issue—for scorching 350 miles in 82 straight hours, running 50 marathons in all 50 states in 50 consecutive days, and for being a fitness motivator and father of two, but now's your chance to get up close and personal.

Meet Dean at the SF Design Center (which is hosting an SF Marathon Expo), where he'll be embarking on his journey or join him at any point along the route. Dean will be stopping to stretch at Crissy Field, where you can hear his training tips and stock up on new products by Joint Juice. And if you're really crazy, you can even cross the Golden Gate Bridge with him as he heads home to Marin. 

Call it a warm up and definitely count me out.

Pre-marathon marathon with Dean Karnazes, Saturday 7/24, 1:30 p.m., SF Design Center, Seventh and Brannan streets.