In ultra trail running you need to keep moving for a long time over changing terrain, eat on the go and maintain a manageable effort. That's why it's useful to set a long run not only by kilometres but also by time on feet. And for a trained runner, back-to-back sometimes works: two long runs on consecutive days instead of one excessively long outing. Both tools serve a specific purpose, not a record in the training diary.
Why hours on feet say more than kilometres
The same twenty kilometres on a dirt road and on a rocky trail with steep climbs are different workouts. Speed is changed by elevation gain, surface, weather, altitude and the need to choose a line. Trying to hit the planned distance at any cost can quietly add several hours of load. A plan by time lets you limit the duration in advance and choose a route with the option to cut the loop short.
For ultra, time is a more universal planning unit, but not a complete measure of load. Four hours of easy movement on a gentle trail are not the same as four hours of technical descents. Along with duration, you need to consider terrain, effort and how familiar the surface is. Descents matter especially: your breathing may stay calm on them even though your legs get noticeably tired.
- Time on feet. The time you spend on your feet: running, walking up climbs, short stops for water and gear. It's not a requirement to run without a break.
- Moving time and total time. Record both. A long lunch on the route doesn't replace movement, though it lengthens the outing and affects your water and food supply.
- Route context. Note elevation gain and loss, trail difficulty and how you feel. Without this, comparing two long runs by hours alone is also imprecise.
Mileage doesn't become useless: it helps you assess the route and logistics. It's just that in a long run for ultra, distance is often the result of a set time and effort, not an obligation you have to speed up at the end for.
How to build a long run by time
Outings of 3–6 hours are a possible guideline for individual long runs in a trained ultra participant, not a starting norm and not a weekly obligation. The lower and upper bounds depend on experience, current load, the difficulty of the future course and recovery. If your usual long run takes an hour and a half, jumping straight to three already means a big leap. First you need stability at a familiar duration.
The main effort is conversational: on an easy section you can say a few sentences without gasping after every word. On a steep climb, switch to walking before your breathing gets heavy. It's better to plan run-walk alternation in advance rather than leaving walking until you're completely exhausted. On technical descents, control of movement matters more than trying to make up the average pace.
- Set a time and a limit. For example, plan about three hours on familiar terrain with a short way home. Such a guideline works only when outings of similar duration have already been mastered.
- Choose one main task. This could be easy movement with walking on climbs or practising nutrition. Don't add a record elevation gain, a new backpack and a fast finish at the same time.
- Start eating according to plan. A long run lets you test the regularity of nutrition and the convenience of packaging long before you get very hungry. The specific scheme is chosen taking into account duration, effort and tolerance.
- Assess more than the finish. Note how your effort, mood and ability to eat changed, and then how the following days went. Finishing an outing successfully and absorbing the load well are not the same thing.
You don't need to replicate the entire expected race duration in training. The longer the long run, the higher its recovery cost and the less room it leaves for the rest of the week. Sometimes a shorter long run with suitable terrain and practiced nutrition solves the task more precisely than extra hours for the sake of a round number.
Back-to-back: two long runs on consecutive days
Back-to-back is a pairing of two long runs in a row, usually on consecutive weekend days. The second starts against the background of residual fatigue from the first. The point is not to endure at any cost, but to train calm movement on tired legs, nutrition, and pacing. This way you can accumulate substantial time on your feet without one very long outing, but the total load doesn't automatically become easy.
For a runner who already handles single long runs confidently, an example might be around three hours on the first day and one and a half to two on the second. This is an illustration of the structure, not a ready-made prescription. Duration depends on your usual week and terrain; the second outing is often made shorter, easier, and with a larger share of walking. Between days you need normal nutrition, sleep, and time to rest, not deliberate under-recovery.
- Who it might suit. A runner with a stable base, experience with long runs, and the goal of preparing for a long ultra distance. It's important that a single long run no longer throws you off for several days.
- Why not for a beginner. While the response to one long run is still unpredictable, a second makes load control harder. First it's more useful to establish regularity and recovery after one long day.
- How often. In a specific block, a guideline might be once every 2–4 weeks, but only with normal recovery. This is not a minimum frequency: some runners do fine with rare pairings, others don't need them at all.
- What changes in the week. The pairing replaces part of your usual load rather than being added on top of it. Adjacent days are made easier, without trying to preserve all fast workouts at any cost.
The decision about the second outing is made anew in the morning, not only when drawing up the plan. If normal walking has become uncomfortable, movement has noticeably changed, or fatigue is unusually strong, the planned pairing stops being mandatory. Shortening or cancelling the second day is part of load management, not a failed workout.
How to add volume and recover in time
Gradualness means growth relative to what you've actually handled in recent weeks, not relative to the shape you want. There's no universal safe percentage of increase. For some, adding 15–30 minutes to a usual long run is a small step, while after a break or on new terrain even that becomes significant. Don't increase time, elevation gain, descent difficulty, and intensity all at once.
The working logic is simple: repeat a load you've mastered, slightly increase one parameter, assess the consequences, and only then decide whether the next step is needed. With your first back-to-back, it's especially important to reduce the other workouts of the week. The sum of two outings should be considered together with all other running, strength work, and everyday fatigue, not as a separate impressive number.
A recovery week can be scheduled in advance after two or three weeks of building, or earlier if recovery worsens. This is only a scheme: with intense work, poor sleep, or difficult terrain, recovery may be needed sooner. In it, you shorten the long run and total volume, drop the pairing and extra intensity. Missed hours are not carried over into the next week.
- Normal effort has become unusually hard. Easy routes require more strain for several workouts in a row, and the desire to move doesn't return after rest.
- Recovery drags on. Fatigue from a long run interferes with the next week, sleep and mood worsen, and you have to regularly cut other sessions.
- Movement changes due to pain. Don't make up time through limping or growing pain. This is not a test of will and not a reason to check how much more you can endure.
Such signs are not a diagnosis, but they show that the plan needs revision. Hour numbers and recovery metrics from your watch are useful as additional context, not as permission to ignore how you feel. With persistent pain or other troubling symptoms, you need a specialist's consultation, not another training test.
Nutrition and gear: rehearsal for a long day
On a short run it's hard to tell whether your vest will chafe after a few hours and whether your usual food will still sit well after a long climb. The long run is there to test the whole system: what you carry, where it sits, how you reach it, and how you restock. It's best to keep conditions close to your upcoming task, but without deliberately shorting yourself on water, food, or weather protection.
- Food. For long runs, a common guideline is 30–60 g of carbs per hour. This isn't a universal rule: needs and tolerance depend on effort, duration, and your experience eating on the move. Count carbs in drinks too, check portion contents, and don't raise the amount sharply just to hit a number.
- Water and restocking. Check flask volume, how accessible water sources are, and your reserve for delays. Usage changes with weather, sweating, and pace; one fixed amount won't fit every workout. Don't force yourself to drink extra just to follow the plan.
- Shoes and clothing. Assess the fit after several hours, chafing from wet socks, access to your jacket, and shoe stability on descents. Comfort in the first minutes guarantees nothing. Choosing a pair for the surface and weather is covered in the article on how to choose tread and when a membrane hurts.
- Vest, poles, and navigation. Test your gear with a real load: does the vest bounce, can you stow poles easily, is there enough charge for the route. For outings in the dark, check your light and power reserve separately.
After you're back, leave a short note: how long you moved, what you ate and drank, where discomfort appeared, and what should change. Next time, test a few clear adjustments rather than a whole new system. A useful long run gives you not just hours in the diary but concrete decisions for your next outing.
In 1trAIner, the AI coach builds your plan as a planning cascade Season → Month → Week → Day. Data from Garmin and Apple Watch syncs automatically, and the week is recalculated after every workout. First 7 days free.
This material is for information only and does not replace a doctor's consultation.
