Recently, I have gotten back into running, so I signed up for a trail running event (16km distance, 650m climb, 650m descent) in 10 weeks and started training for it. I have some experience in training for and participating in 10ks and half marathons. For the time being, I'm trying to modify a cookie-cutter half marathon training plan for this specific run (If it's relevant, it is this one: Profi-Trainingsplan Halbmarathon, german only).
According to rules of thumb, the distance roughly checks out (add 700m-1000m distance per 100m climb => 20.5km - 22.5km for my run). But the program - like many others - don't really take climbing into account, so I'm sure there's a lot of room to improve specificity of such plans.
My question is:
How does a trail run differ from a regular running event of equivalent distance, and how do I take those differences into account when designing a program and during the race?
Some particular points I'm wondering:
Determining an intended pace for a run and checking whether you're on par during the race is relatively straightforward for a flat-terrain event. How do you properly set a goal for a trail run, and how do you keep track of where you are regarding that goal?
How much of the training and which types (long slow runs, tempo runs, intervals,...) should take place in hilly terrain, how much of it should stay in the flat?
- Is a consistent speed preferable, or a consistent heart rate?
- I learned the hard way that running downhill is deceptively easy on the cardiovascular system but incredibly taxing on the muscular tissue. Should downhill runs be incorporated in the training? How?