I have my first mud run this weekend. The course is designed by Spartan Race but it's for the biggest loser race series. Has anyone done any mud runs?

Not yet, but want to do a tough mudder next year. I heard these are a bit long at 12 miles with obstacles (think: boot camp) and lots of mud.

I did! I did the King of the Hill 5k Muddog -It was a blast, although I did NOT run after the first couple minutes, it was on a huge hill going up, then down, then back up and over etc... I was unable to do many of the challenges like climb over big walls or the rock climbing one..but I was able to take the option of doing push ups instead of the rock walls. I was able do other smaller challenges like crawl under the barb wire, and jump over small hurdles and cross a net..(not as easy as it seems)I knew going in I wasn't physically able to RUN a 5k but I went with the intent of having fun. Took the kids as well for the kid's course and we were a muddy mess when we got home

You will have fun and just go in knowing you're doing something healthy and outdoors regardless of how much you can or cant do. Have fun!