Training for an adventure race varies greatly from individual to individual, depending on your current fitness levels and what you want to achieve. However, whether you are going for the prize or are simply participating for the thrills, here are a few points that should help you out.
1. Focus on a range of cross training activities so that your overall fitness levels increase, and you are better prepared to handle different parts of the race.
2. Know the requirements of the race you will be participating in and base your training on that.
3. Adventure races don't necessarily take place in sun 'n shine. During training, make sure you go out in unpleasant weather so you are better prepared during the race.
4. Start slowly and gradually build up so you don't burn yourself out.
5. Finally, if it gets too much to handle in the beginning, take the help of a professional or somebody who has been a regular participant.
So - best of luck with that training & do let me know how it is going!
I admire anyone who is overall healthy enough to even compete/participate in an adventure race. It really is for people who make fitness a complete life commitment. I wonder if there's anyone who's new to the fitness world who competed just for the heck of it and how that went. I think I'd be really embarrassed when I couldn't even climb over a wall or something. :)
There are lots of shorter events in adventure racing-- they don't all have to be 24 hour races. Big Blue AR series has some shorter races. I hate mountain biking downhill, but my good friend started this www.baarbd.org as an AR site to find training partners in the Bay Area, but also to introduce people to the sport.