Over the following months and weeks you will start to see the details of our training plan, but it's worth taking a minute to talk about what an off-road endurance race entails and how that instructs a training regimen:
Off-road endurance is mostly about climbing. Your typical stage race is 250-400 miles, with upwards of 50,000ft of vertical gain. Taking the TransRockies as an example (~350mi, ~60,000ft of vertical gain), if you averaged out the climbing for each day into one uphill and one downhill, every single day would be a giant category 1 climb (in roadie terms) and corresponding descent. Since you're not actually climbing or descending all the time, climbs are even more intense when they happen, with uphills of as much as 15% grade for 2-3 miles being a common occurrence.
Looking at this merely in terms of physics, it is clearly important to take as little with you as possible. Take, for example, a bike and rider that weigh 85kg (187lb) together and can generate 250w of power on average, while climbing, over the course of a race. Put him on a steep 1000m climb. By the equation
TimeToTop = (MassOfRider * AccelerationOfGravity * HeightOfClimb) / (Power - 10%)
(The 10% subtracted from power is merely a catch-all for the stuff we've left out like friction and wind resistance)
this rider would take just under 61:45 to complete the climb. Now give the rider a few beers and cheese sandwiches (+5kg), do the same math and you get 65:20. Multiply that difference over a week with 18,000m of climbing and you have 65:30. Don't take that number as the word of god, but it adequately makes the point that minimizing your excess body mass (fat, mostly) can mean HOURS in the course of a stage race.
As mentioned above, much of the climbing in an off-road endurance race will be at grades above 10%. Experimentally, most well-trained cyclists prefer a slower cadence while climbing steep grades than on the flat for the same power output. Though it us unclear exactly why this is the case, it does not affect the natural conclusion that courses with more climbing will put more strain on your muscles for the same amount of work performed than flatter courses will. By addressing this fact aggressively in your training through exercises that test muscle endurance, you can help to delay muscle fatigue on long stages and during long weeks.
Finally, it goes without saying that a cyclist's aerobic performance is of huge importance in endurance racing. A cyclist training for endurance events should specifically target exercises that challenge the aerobic threshold for long periods of time. For experienced cyclists, this will be the majority of the focus in the base period. For newer cyclists this training could be as much as 75% of your workload.
Though the above all address physiological characteristics, a successful training program must also address technique. Powerful seated climbing and efficient pedaling will help to fight muscle fatigue and enhance aerobic endurance, while good bike handling and line finding will help a rider carry momentum, minimizing energy loss. All of these skills should be visited throughout the training year by designing workouts that stress technique in addition to the physiological characteristics mentioned above.
Now if only I could get off the couch and actually try some of this stuff...