Burro racing in Colorado is back for the season

If trail running sounds tough, try it with a 400-pound donkey in tow.

Driving the news: Burro racing — Colorado's official summer heritage sport — is back this year with two "Run Your Ass Off" events scheduled this weekend.

• Georgetown hosts an 8-mile trot through town and up into the hills tomorrow.
• Idaho Springs follows with a 5-mile stampede race Sunday.

How it works: Runners in these races can't ride their burros, but must coax and cajole the famously stubborn animals to keep pace.

• No burro? No problem. Rent one for $175.

The big picture: Burro racing is growing in popularity with runners in Colorado and beyond.

• It started as miners' pastime — hauling gear over rugged terrain — but has become a beloved (albeit eccentric) Old West throwback.