Proud Mount Sanitas—the northern terminus of the Skyline Traverse, a classic Hinge date destination, testpiece of any Boulder uphill athlete—is just down the road from my house. Almost every week, my friend Jack and I do a lap before or after work.
During one of those Sanitas seminars, between yapping about our latest deals at work and planning weekend adventures, we conceived of an idea. This idea was nothing novel. It represents no innovation or creativity. The only degree to which it was notable was how dumb it was. That was the point.
“What if we did an ultramarathon of nothing but laps of Mount Sanitas?”
Between the two of us, we figured we knew enough people committed to the bit, folks with questionable mental health, and/or hardos to convince a few others to join us in this conquest of the useless. And so, with the aid of the talented Taylor Woolley, it is my honor to introduce:
Slos, or Several Laps of Sanitas, is an 50k race in Boulder, Colorado. Starting in my backyard, racers will run to the Mount Sanitas trailhead, follow the Mount Sanitas trail up the south ridge to the summit, descend Lions Lair and Sunshine Canyon back to my house, and repeat, five times. Or fewer. It doesn’t really matter. You have to touch the fence for a lap to count.
My house will serve as the starting line, finish line, and aid station. People will be grilling in my backyard and drinking beers while we run, doing their best to tempt us away from finishing the prescribed 5 laps.
DATE/TIME
May 3rd, 2025 - 7:00 am
START/FINISH/AID STATION
Mapleton Hill, Boulder, CO
MAP
DISTANCE
1 Lap = 6.76 miles, 5 Laps = 33.8 miles
ELEVATION
1 Lap = 1,379 ft, 5 Laps = 6,895 ft
FREQUENTLY ASKED QUESTIONS
How do you pronounce “Slos”? ‘Slos’ rhymes with ‘boss.’
Is there a prize for winning? Maybe. Probably. Almost certainly there will be something for the person who travels the farthest to run with us. Seems like there should be an award for “best outfit.” Perhaps a “slowest finisher” award. No promises on anything.
Is there a cut-off time? Absolutely not. You can run all night if you want to.
Is there a mandatory gear list? You should probably wear shoes, but I understand some people swear by barefoot running.
Do I have to sign up? Please sign up here so we know how many people are showing up.
Do you have to run all five laps? No. You don’t have to do anything. Why are you even thinking about doing this “race”? You can join for five, one, none, or ten for all I care.
Is this a commercial event? No. This event is pure masochism—we will derive absolutely zero financial benefit.
Will there be merch? Maybe. Depends on how many people sign up and if there is interest. Taylor made some sweet art.
Will there be treats? Water, snacks, post-race beers, & vibes will be provided. With that said, donations of matériel are appreciated.
What if I have a question that isn’t covered here? Ask it in the comments. Send me an email. I’ll update the FAQ as needed.
Sign up here:
Race updates via the instagram @slos.run & via email once you sign up.
Remember that trying hard is good, actually. See you in May.
contender for favorite race announcement of all time
Love this. If I didn’t have to get 8 hours of sleep each night that weekend, I’d sign up.