Trailrunning - What special considerations have to be made compared to regular running

Question

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?

Answer 1

Trail running challenges

Running on trails and hills is harder in a few ways:

• Mental challenge. You have to pay attention to each step to avoid rocks, roots, uneven ground, etc. This mental effort can be exhausting on longer events. You may also need to find your way on a new or poorly marked trail, which can be stressful.
• Strategic challenge. On a flat road run, you can apply a gradually increasing pace throughout, and as long as you don't start too fast, you'll do well. On a trail run, you have to determine how hard to take each hill as you approach. Early errors in judgement add up over time.
• Cardiovascular challenge. Long hill climbs will tax your heart and lungs.
• Strength challenge. Steep hills require strong quads. Rolling terrain and sharp turns require calves, ankles, and feet.

As someone who has complete four trail marathons, my key piece of advice is always run on trails. You're going to be challenged in four new ways compared to a road run, so you need to practice as much as possible.

Training strategy

• If you track it, heart rate is more important than pace. But without a HR monitor, gauging relative effort is often enough. Slow down a bit on the hills, and let your heart slow down some before picking the pace back up.
• Setting a goal will be difficult unless you've trained on the course or run a very similar event. Even then, changes in weather or trail condition can have a huge effect. As you progress through training, you will also work on setting a goal. On race day, be ready to adjust this if the weather is warmer/cooler than expected, or if the trail is wet.

Training terrain

For each different type of "classic" running workout, here's what I suggest:

• Tempo runs. Terrain isn't too important here. I'd focus on a course you can visit regularly. If you're used to the terrain you can adjust your effort accordingly to get the tempo effect.
• Speed work. Look for a course with short, steep climbs. A hard climb is just as good as a fast lap on a track. For longer climbs, it's OK to walk for a bit instead of slowing to a jog.
• Long runs. The ideal long run course has a few good long, flat sections, and a few long, gradual climbs. A long (or steep) climb near the end is also important: it helps gauge your body's ability to keep pushing after using a lot of energy (which helps build your confidence). I also try to avoid walking as much as possible on long runs, so that I get used to being exhausted.
• Recovery runs. Try to avoid steep climbs, or walk these portions.

Race strategy

• Walk up the hills, and fly down. Walk the early hills to keep the race adrenaline from burning you out too quickly. Toward the end, if you feel up to it, running them is fine. In training, I try to avoid going too fast on the downhills, to avoid injury. But on race day, this is where you go all out (just try not to run into anyone!).
• Carry food and water. Aid stations will often be placed where convenient for volunteers, and may be crowded with other runners. This means you might have to slow down at a part of the course where otherwise you'd be looking to make up some time. Having your own food and water means you can skip some of the aid stations.

Answer 2

So, after having partaken in the trail running event, LShaver's great answer has proven to be very helpful during training as well as during the race itself.

Here are some additional thoughts and findings that I made:

Equipment

• Trail running requires different shoes than running on streets.

• The sun shining through the forest's treetops often made it difficult to spot details like roots or holes in the trail. Contrast-enhancing sunglasses help.

• Applying insect repellent when running through the forest isn't a bad idea, either.

Training routine

• I'd like to object to one point of LShaver's answer: I think it is necessary to go fast on a descent from time to time during training period. It's a pretty unique kind of physical strain that requires a lot of concentration and technique. It requires quite some recovery, so plan accordingly.

• Running downhill also put a lot of stress onto my bowels. Twice I had to interrupt my training in order to find a place to poop. Never happened to me during runs on streets and/or flat ground. Glad I practiced running descents on trails before so I could find out I'm susceptible to that before the actual race.

• I feel like strength endurance training is even more important here than for regular running to handle the taxing ascents and descents. Don't skip it.

• Just like road bike cycling is beneficial to running, mountainbiking is a good addition to trailrun training whenever the program says "cardio". XC style biking helps improving aerobic baseline, while gravity biking builds strength endurance and teaches useful mental skills like line choice. I do a lot of enduro-style biking and feel like I get the best of both worlds.

• It has been said before, but it can't be stressed enough: Always run on trails. And get accustomed to running steep uphills. Running a trail with 20% climb at 90% HfMax feels entirely different than running intervals at that heart rate on a track.

The Race

• If you're like me, you should take all measurements to ensure you don't need an urgent toilet break during the race. Taper your fiber and fat consumption, don't overdo the hydration, experiment with Imodium,...

• Unlike a regular race event, determining a race pace and trying to maintain it is not really feasible on a trail run. What I did instead: I used a rule of thumb (100 metres of climb are equivalent to an additional 1000m of horizontal distance) to figure out what would be the flat-land equivalent distance to the race's track profile. I took my race pace of the closest common race formats (in my case: half marathon) and ran that pace several times during preparation for a few kilometers. I tracked my average heart rate for that pace - this would be my target heart rate for the actual trail run, +/- 5bpm.

• Pay attention to your concentration level. The race I participated in ended with a descent of 100 hm on narrow single trail. This is where you usually do your final sprint, but it's also when you are already tired from all the km you ran before, which makes that section particularly dangerous. One participant got a sprained ankle half a kilometer before the finish line. Play it safe there!