Re: Training -
Now that I've done something like this,
I think one of the pillars for training is make sure that you're on your bike almost every day, even for an hour. This does not mean you're doing centuries every day, but get on your bike and ride it. Take rests when it's required and keep the fast days fast and the slow days slow and recover with recovery rides. If you're at race-pace on the GDMBR, you're not going to have a day off. Your body needs to adjust. Doing the TD is not extremely healthy to do and your body will pay the price, but get it prepared. I think splitting up the workout and doing half the time in the morning and half, like after work is an interesting idea. Train yourself psychologically as well. Get it used to be on the bike all the time.
Try out some theories on training, like periodization. There's a lot of resources out there on things like training for something like the Paris-Brest-Paris, or the RAAM that work well with the TD. The TD, although it's on dirt, is really differentiated by the amount of climbing done (not saying anything about the self-supported part of it). Fit a ton of training on hills - no amount is too much, really. If you can work up to 10k of climbing in a day, you're in good shape for the TD.
NOT THAT I'M SAYING I'M GOING TO, but if I did the TD again, I'd be a little more disciplined with my wakeup times, especially to fit training in and be somewhat of a sane human being afterwards. 5:00am every day to get a good ride in. Trying for 300 miles/week would be nice, but keep those miles "useful" - fast on fast days, slow on slow days. More important than amount of miles. Don't waste your own time! Keep a diary of your training, what you did, how you felt, what goals you have and remember to keep it somewhat structured. Work around important things in your life and adapt your training to your life, and not the other way around. If there's something in your life that you need to devote 4 days off to, that's a grand time to end a major chunk of periodization, allow your body to get an incredible rest and allow you to be stronger when you start ramping up again.
* I would put in more fast, short days than I did.
* I would do some actual 24hr races
* I would certainly keep the fluid trainer around, as it's a great helper with working with real-world schedules. As I wrote, try to ride (or work up to try to ride) almost every day. There are many stretches of the TD that are nothing but pounding out miles and the fluid trainer is perfect for that.
* I would keep going to the gym, especially when the weather is bad, the roads are bad and there's not much daylight, but taper that off to almost nothing, once race time nears - it's good advice to train specific to your event and if your event is riding your bike (and, uh, pushing your bike, sometimes), keep that end goal in mind. I worked on a lot of core strengthening stuff, which I would do again, and maybe more neck strengthening exercises. It's amazing how heavy a helmet can get with a few lights attached to it. Sprinting/Plyometric work as well. Make sure you're not gaining TOO much muscle weight, it's not going to be useful, so look for advice on athlete specific training programs and not programs for body sculpting (working towards complete exhaustion of your muscle groups in heavily isolated exercises will help little with ultra events).
* Other than the gym and riding bikes, I'd mix it up as before with hikes and snowshoeing and running, working muscles a different way than normal to prevent overuse injuries and keep things supple.
* Work with what you've got in terms of terrain. I'm pretty lucky to live 10 miles from the front range of the Colorado Rockies, but it's still 10 miles there and 10 miles back if I want to ride any type of singletrack. I used those long fairly flat times to get used to pounding out miles, working on cadence and smooth pedaling.
Learn about your equipment and endlessly tinker with everything until it's to the point of a natural extension of your own body. Simplicity of gear I think is pretty paramount in importance. Dropping weight really does help matters out. Get comfortable sleeping on the ground. Really. Learn about your body and food. Maybe try different types of diets with varying %'s of macro-nutrients, but understand it's going to be less than ideal on the route. I'd almost side on upping the % of fat, as you're going to get some greasy sides on the route, but there's also a theory that one can train your body to use what it's used to using and if you eat a fat-rich diet, your body will use its own fat stores more efficiency. Again, "theory" though, YMMV, and all our bodies are different. Research, research. Experiment.
And keep it fun.