I have done this and I would do it again if I were in the same situation. I had signed up for a 70.3 and got injured. I could still swim and bike, just not run. Since I had already signed up and was definitely going to go to the race since it was my husbands first 70.3 I decided to race anyways. I raced the swim and bike and walked the run. It was a long walk, but I actually had a blast with it. I talked to people walking around me, I saw many BOP's struggling and working hard to finish, and really just had a good time. I think the nice thing about it was that there was no pressure to be fast, I could just hang out and enjoy myself.
The mistake I made was assuming that since it was just walking I didn't need to train at all for it and it would be no big deal. Well walking 13.1 miles turned out to be a little harder than I expected. This is the only time I have ever cramped while walking and I found myself pretty sore the next day. So, my recommendation is to train some for the walk!
If you choose to give it a try, have fun and good luck!
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