Training for Mountain Running

To be most effective, training for mountain running needs to be viewed differently than road or track running.

Mountain running and road running are, at best, distant cousins. Yes, both are “running,” like freestyle and butterfly are both “swimming ” but require different techniques.  Running is a form of locomotion that contains a flight phase, where both feet are off the ground at the same time, and only one of the runner’s feet touches the ground at a time during the stride*. Both road and mountain running fit this definition. But that’s where the similarity ends.

*whereas in walking, there is a time during the stride when both feet touch the ground.

Training for mountain running and running on flat, smooth ground share only passing similarities. This article will explore the variety of training methods that mountain runners should employ.

When running on smooth, flat ground, be it road, track, or trail, every stride the runner takes will be virtually identical to all the others. This makes learning and perfecting the technique of running simpler to master and simpler to train for the repetitive movement.

Mountain running, which is almost always conducted on rough trails with significant and often frequent gradient changes, necessarily forces the runner to adapt the technique to the terrain. There will always be a great deal of technique variation during mountain running. Some flat sections of the trail may require a running technique identical to road running technique. However, the technical and fitness demands differ significantly for uphill sections, where “running” can look more like climbing a set of stairs, and runners are often forced to walk. On downhills, the runner must resist gravity lest the speed become so great that a fall is unavoidable. Resisting gravity in this way means that the impact forces the runner’s legs must absorb are much greater than running on flat ground. The trail’s roughness will greatly affect the runner’s stride length, frequency, and height each foot must be lifted over obstacles.

Technique

Mastering any technique takes time and focus. Mastering four different techniques requires considerably more time and focus and will require prioritizing how that time is spent. Flat running, uphill running, downhill running, and uphill hiking are four different means of locomotion needed to be a mountain runner. From the standpoint of muscle recruitment patterns, each is its own “sport.” Each requires a different training method, presenting the mountain runner with a bigger challenge in allocating training time and energy. And we have not even mentioned the use of poles for steep hills where they can make a substantial difference.

Swimming faces a similar challenge. If a swimmer wants to be competitive in the individual medley event, they must train all four strokes, which, even though they are all “swimming,” are distinct techniques that each need to be trained in isolation.

Why all this talk about technique?

A good level of fitness is, of course, what will allow you to run a sufficient volume needed to handle long runs in the mountains. But good technique will allow you to cover that distance faster and with less energy.

Flat

Runners who are making a transition from the road to the mountains often bring with them good flat running technique and speed. This can be a significant advantage. One of the technique boxes has already been checked. These runners have developed both the technique and fitness to run substantially faster than they need to run in the mountains. That speed component is another helpful box to have checked. Mountain runners without a road or track background often struggle with their pace on the flats. Running fast* on the flats requires its very own type of strength and muscular endurance. Tendons act like springs in that they can return much of the energy they are loaded with. This is why high-level runners appear to be running so effortlessly. They have learned how to extract more of this spring energy.

*Fast here means relative to the individual runner.

Uphill

This is where most people’s attention is focused when they think about mountain running, and for good reasons. Uphill running speed relies less on technique and more on fitness. Depending on the gradient and the trail’s roughness, uphill running speeds can easily drop into the 20-30min/mile range. This means you may take 2-3 times as long to cover a mile uphill than on the flats or downhill.

Let’s take a hypothetical 60km loop mountain course that has a mix of 25km on up hills, 25km on down hills, and 10km on flats. You could easily spend 60-75% of the race time going uphill, even though this course’s distance is only 40% uphill. Simple arithmetic tells you that you can gain or lose the most time in the up hills. This is why uphill fitness gets so much attention from mountain runners. When Ruth Croft set the women’s course record of 8:03 at the 2024 Transvulcania 100km race, she spent over 5 hours, or 66% of the time, going uphill.

Downhill

We can’t talk about downhill running without speaking about the Impact forces of running because these heavily influence training for downhill running.

The force transmitted through the leg each time a runner’s foot strikes the ground on a flat grass surface at about a 9min/mile pace will be about three times their body weight.

Running at the same 9min/mile pace on a rather typical 9% downhill gradient, the total (normal + parallel vectors) impact force will more than double what would be in the flats. https://www.sciencedirect.com/science/article/abs/pii/S0021929004002283?via=ihub

That force has to be absorbed primarily by the leg muscles and tendons each time your foot hits the ground. For most runners, this means 5-6 times their body weight when landing on each foot when running down a typical trail. Absorbing that impact force is done with eccentric* muscle contractions. At these high-force eccentric contractions, muscle damage is easily induced. Is it any wonder your quads get sore when running downhill? Training for this requires its own unique form of strength training that can be done on the trail or in a gym.

*Eccentric contractions are those where the muscle lengthens under force. These can produce higher forces than concentric contractions, where the muscle shortens under force.

Walking Uphill

As the grade of the trail steepens, at some point, it will become more efficient to shift from running to walking. You’ve no doubt felt it when you reach this point going up a hill that steepens. This is important when you are on a long climb or are out for several hours. You don’t have extra energy to waste; balancing the most economical mode with the fastest speed can be a critical decision.

At grades steeper than about 20%, running no longer includes the flight phase, where both feet are off the ground during the stride. So, even though it looks like running and has a higher stride rate than walking, it no longer fits the definition of running.

At what grade do runners make this transition to walking? This depends on several factors. These include: the length of the hill and how long the runner has been on the trail, leg length and strength, but most importantly, the runner’s local muscular fatigue. While you can’t change the length of your femur, fatigue resistance is highly trainable.

Of all the studies I can find on walking vs. running uphill, only a tiny handful, all conducted by an even smaller number of researchers, have used elite mountain runners and relatively short testing times. One study is mainly concerned with world-class Vertical Kilometer racers, race courses that typically average over 30% grade, and races that last 30 minutes. There is nothing wrong with investigating this, but we can’t draw meaningful takeaways for runners doing far more common events that last many hours.

The duration of the individual climb and how many hours you have already been on the trail are hugely important to your walk/run decision. Fatigue plays the most critical role in long-distance running, especially when deciding when to walk and when to run. The more tired you are, the sooner you transition to walking as the grade steepens. That’s why we can’t just extrapolate from a study that looks at steady-state tests lasting a few minutes. These tests give accurate heart rate and VO2 data so that the relative energetic costs of running and walking can be compared for different grades and speeds. But do these tests reflect what happens after the runner has been on the course for many hours? If our experience coaching many mountain runners is any indication, these studies do not give meaningful information on multi-hour events.

Here is some reference material on running vs. walking uphill. While the articles and studies mentioned are well done, I don’t think these studies provide useful information for athletes running in multi-hour events. I am including these so that readers will understand that this subject has gotten some attention from scientists:

• Jinger S. Gottschall, Rodger Kram – Ground reaction forces during downhill and uphill running

• Keely Henninger – Climb the Mountain: When to Run, Hike, or Pole

Performance Limiters

You have limited time to train. More importantly, you have limited energy to devote to your training. You want to apportion your time and energy in the most effective means to yield the best returns on your time investment. To do that requires an analysis of the demands of mountain running.

Mountain running for durations longer than 3 hours will, of necessity, be conducted predominately at relatively low intensity. Mostly in Zones 1-2, with some short forays into Zone 3 and only tiny amounts of time in Zone 4, if at all. By using fats and carbohydrates as fuel, your aerobic metabolism will provide virtually 99% of your energy demands for running at these submaximal paces. The fatigue from running long distances in the mountains comes from the duration rather than the intensity of exercise. It should only be in the last hour of a 4-hour run that you begin to feel fatigued.

Below are three real-world examples of the training data from six months’ worth of training by some of the top ultra-runners we coach. Notice the intensity distribution as measured by time in the zone. This information comes directly from their Training Peaks logs.

• Runner #1 Zone 1=40%, Zone 2= 52%, Zone 3=8%, Zone 4<1%
• Runner #2  Zone 1=35%, Zone 2=54%, Zone 3=9%, Zone 4<2%
• Runner #3 Zone 1= 45%, Zone 2=44%, Zone 3=7%, Zone 4<1%

Real-world examples of those same runners’ typical intensity distribution in races of 100km or longer:

• Runner #1 Zone 1= 6%, Zone 2=76%, Zone 3=18%
• Runner #2 Zone 1= 18%, Zone 2=62%, Zone 3=19%
• Runner #3 does not wear a HR monitor when racing

These elite pros spend 90% of their training time below their aerobic threshold (AeT) or at the top of Zone 2. They do this because 80% of their race time is spent in those same intensity zones. If your training intensity distribution deviates a lot from theirs, this is the first place you should focus on to improve the effectiveness of your training.

We have seen that one of the best predictors of ultra-distance performance is one’s speed at the aerobic threshold (AeT). That’s because your AeT is an intensity you can sustain for hours. This does not mean you will not become fatigued after hours of AeT-intensity running. Nor does it mean that training above your AeT is unimportant. Both of these points will be discussed in later sections of this article.

Fatigue Mechanisms

Fatigue of all forms manifests as a reduction in muscle contractile force. The result is that your stride length shortens, and you slow down. Fatigue mechanisms are lumped into two categories: Central and Peripheral.

Central fatigue is a neural effect that affects the brain’s ability to recruit and fire the propelling muscles with as much force as when rested. This effect can be caused by the motor cortex or all the way down the nerve path to the individual motor units losing the ability to produce sufficient force to maintain the desired pace.

Peripheral fatigue is caused by changes within the muscle cells that reduce the muscles’ contractile force. Glycogen depletion is the most well-known of these. However, metabolite accumulation and muscle pH reduction (acidity increase – the burn erroneously attributed to lactic acid) are other commonly understood factors in peripheral fatigue.

 In this case, the distinction between central and peripheral is a somewhat artificial construct, as these two systems are inextricably linked and interdependent.

In any endurance event, training aims to increase the athlete’s fatigue resistance. Fatigue resistance is a somewhat amorphous term and a combination of many training adaptations. As such, it can be hard to determine what factors contribute to increasing fatigue resistance.

However, studies have documented that the fatigue resistance of the main propelling muscles is not well correlated with VO2 max. In other words, having a high VO2 max does not guarantee fatigue-resistant legs. However, a higher fatigue resistance allows the runner to sustain a higher speed, utilizing a higher percentage of their VO2 max for longer.

This concept is closely related to the many terms that have been applied to the athlete’s maximum sustainable speed: Anaerobic Threshold (AnT), Maximum Lactate Steady State (MLSS), Lactate Threshold (LT), Second Ventilatory threshold (VT2), Critical Power or Pace (CP), Functional Threshold Power (FTP) just to name some of the more common terms. Despite the bewildering array of names, they all stand for the maximum speed (or power) the athlete can sustain for 45 minutes to 1 hour. Metabolically, it is the fastest pace/highest power at which the lactate removal rate equals the lactate production rate. Hence, the MLSS term.

Famed running coach Renato Canova has stated that the most significant limitation to speed at this MLSS intensity is Local Muscular Fatigue. Increasing resistance to local muscular fatigue should be part of every endurance athlete’s training strategy.

What causes you to slow down when your mountain run continues over many hours?

We have a lot of data for mountain runners in many races, including podium finishers in some of the most competitive races. One prominent trait that runners of all abilities have in common is that as local muscular fatigue builds late in long races, we see a significant drop in heart rate.

An example of a UTMB podium finisher:

• On a 45-minute 16% climb 3 hours into the UTMB: avg HR=156. Avg pace 17min/mile
• On a 1hr 18% climb 1/2 way through UTMB: avg HR=130. Avg pace ~20min/mile
• On a 1hr 17% climb late in UTMB: avg HR=120. Avg pace ~20min/mile

Heart rate and oxygen consumption have a nearly linear relationship at sub-max efforts. This means that in the aerobic intensity realm (zones 1, 2, and 3), if you increase the heart rate X%, you will see a Y% rise in oxygen consumption (VO2) throughout these intensity zones.

Because of this linear relationship, we can estimate the oxygen consumption of these athletes during races. At heart rates exhibited late in long races, even top athletes only use 65-70% of their maximum aerobic power (VO2 max). Their hearts have way more pumping capacity than their legs can utilize as local muscular fatigue builds late in the race. Their speed is not limited by how much blood/oxygen the heart can deliver. Their speed is limited by the muscles’ ability to utilize that oxygen.

Because it takes less oxygen to run slower than faster, as their main propulsive muscles fatigue and the runner slows, the demand for more oxygen decreases, and the heart responds by lowering its output by reducing the heart rate. The phenomenon responsible for this decline in heart rate on oxygen consumption is Local Muscular Fatigue.

Therefore, improving the fatigue resistance of the main propelling muscles will allow the athlete to utilize a higher % of their VO2 max and climb faster, especially later in the race.

NOTE: While it is true that these athletes are racing at a fraction of their maximum aerobic power, 65% of a big VO2max is a larger number than 65% of a small VO2max.  So, having a high VO2 max is a benefit. However, it may be impossible for experienced runners who train consistently to increase their VO2 max at all or only by less than 5%. In comparison, that same runner may have the possibility (with proper training) to improve their fatigue resistance by 20%.

Key Training

Regarding any multi-hour event, from our experience, and the conclusions we can draw from the above discussions, we have found this simple training approach: 1)The athlete’s speed at their aerobic threshold and 2) Improved fatigue resistance of the main propelling muscles. These two points are listed in their relative order of importance

 Speed at Aerobic Threshold

When athletes are aerobically deficient, they will not have the aerobic capacity to support running at anything but very slow speeds. Simply improving the aerobic capacity will dramatically increase those runners’ speed at their Aerobic Threshold. Why is the aerobic threshold speed so important? That is the intensity at which you will run for more of your race. This can be accomplished in only one way: running a lot at an intensity commonly called Zone 2.  We often see the aerobically deficient runner’s speed at AeT increase 20-30% within 6-12 months of consistent Zone 2 training. Results will vary based on genetics, age, and training volume, which are the big three. This speed change comes about primarily due to these three adaptations in your muscles: 1) An increase in the mitochondrial mass. 2) An increase in the capillary density in the working muscles. 3) An increase in aerobic enzymes in those mitochondria. Rodent studies have shown a doubling in mitochondrial mass in the working muscles after just a few months of training. During this aerobic base-building period, strides should be included in your normal Zone 2 runs and hill sprint workouts.

The well-endurance-trained athlete with a high AeT as measured by HR or pace (one whose AeT and AnT are within 10% of one another) will use a different approach. To improve their speed at the aerobic threshold, this runner needs more Zone 3 intensity in their training and must be cautious of doing too much Zone 2. Contrast the aerobically deficient runner mentioned above who can do a high volume of Zone 2 because their pace will be relatively slow (and less neuromuscularly taxing) with the aerobically strong runner whose AeT running pace can exceed 5min/mile, imposing a much higher neuro-muscular load that requires more recovery time or less volume. This faster pace will mean the stronger runner needs fewer Zone 2 runs and will fill in that time with Zone 1 runs. Refer back to the three pro runner examples to see that they do 35-45% of their training in Zone 1.

 Fatigue Resistance

Once one’s aerobic house is in order, improving local muscular fatigue resistance becomes the key to unlocking better performance in ultra-endurance events. As explained above, ultra-endurance events are conducted at sub-maximal intensities, primarily in Zones 2 and 3. Because of this, fatigue, typical for shorter endurance events, does not play much role in ultras. This means you will not be dealing with the accumulation of metabolic by-products or drop in blood pH associated with fatigue in shorter races like a Vertical Kilometer or a 10km road race. However, keeping up with carbohydrate use through race feeding can be a big challenge for many long-distance runs, resulting in peripheral fatigue.

While sports scientists are very interested in identifying the source of fatigue, either central or peripheral, coaches and athletes just want to improve performance. Several methods of improving fatigue resistance of the main propelling muscles exist.

Training Methods

At its simplest level, all endurance training is designed to increase fatigue resistance. It is a general rule of thumb that the athlete who does the most work in the least time during their training will get the greatest boost in fatigue resistance. Several caveats accompany this: the work must be specific to the event being trained for in intensity, duration, and modality. For example, swimming 10x100m repeats at a Zone 4 intensity means doing much hard work. Still, these will not significantly help improve the work capacity of an athlete training for a 100km mountain running race.

If there is one thing we know about all successful long-distance runners, it is that they run a lot. That has been the foundational element that all endurance sports share. The best athletes are almost always the ones who train the most.

Indeed, if you are new to long mountain running, you must slowly build up to getting a lot of miles along with elevation gain and loss into your legs; if you are targeting a certain distance that exceeds anything you have done before, you must build not only the endurance to cover that distance but also the confidence that comes from knowing that you will make it to the end.

Increasing training volume is a time-honored way of improving the athlete’s fatigue resistance in all endurance sports. However, running those mega miles takes a toll on your body that can break some less gifted athletes. Newer or amateur runners with much more limited available training time and less tolerance to very high mileage programs can benefit from adding a different type of stimulus.

Likewise, for the experienced mountain runner with years of high-volume training history, piling on more distance each week will eventually lead to diminishing returns on the training investment and potential injury. Why is that? Those athletes are likely approaching their limits in terms of genetics and time and energy allocation that the same training stimulus will give. These runners must look for new stimuli if they want to continue to improve.

If you feel like you have ridden your current training horse as far as it will take you and are looking for some new ideas, keep reading.

The typical way to add this new stimulus and potentially reduce the training volume is to add high-intensity running to the program. Unquestionably, high-intensity running will increase fatigue resistance at sub-max speeds by increasing local muscular endurance. The downside to using training above the MLSS very often is the global fatigue that comes with it, limiting the overall training volume.

Instead of asking our runners to train using Zone 4 interval-style workouts, we use two proven, successful methods.

Muscular Endurance Workouts

These training sessions target those pesky main propelling muscles by overloading them with low resistance/high repetition “strength” training. This article goes into some depth on the subject. In brief, this process works by working those muscles at an unusually high resistance level for many repetitions. The number of reps per workout can range from dozens to a few thousand for the elite. The extra resistance forces the limitation of the athlete’s speed and duration under load to be the local muscular fatigue. While these workouts have a profound training effect and local fatigue. However, they do not impose a heavy global fatigue load and, as such, do not require a reduction in overall training volume.

We rely heavily on a block of this type of training as a precursor to beginning a more traditional interval training program. By elevating fatigue resistance, the athlete can handle a higher volume of conventional interval training with an even better effect.

Threshold Training (Zone 3)

We are using conventional naming for this type of training. However, what we mean by it may differ from your understanding. There is controversy over the best approach for raising the MLSS/AnT speed. Some feel it is most effective to train slightly above the top of Zone 3 (what we term the AnT). Having experimented extensively with Zone 3 and 4 training, we find that using even lower Zone 4 intensity in the interval sessions has a much higher global fatigue load than training in mid-Zone three and requires significantly reduced training volume in the target intensity zone.

Controlling the intensity of this sort of training is paramount. We are trying to target a specific metabolic effect by approaching the metabolic MLSS without stepping over the line. We use blood lactate measurements to ensure we hit the correct intensity. However, it can be done by carefully identifying the AeT and AnT paces and HR and training in the middle of Zone 3.

For the high-level runner, this method allows them to include two-plus hours of work at this intensity in a week. In comparison, getting more than 30-40 minutes in Zone 4 weekly is challenging for even the most well-conditioned athlete and risks pushing the athlete into an overtrained state. Our experience has been that a higher volume of Zone 3 done this way is very effective in improving fatigue resistance and can be the ultimate preparation phase for the ultra-endurance runner. It can also serve as the next to final stage of training for those doing races shorter than 2 hours.

We’ll leave you with these final words. None of these cool-sounding, sexy training ideas amount to a hill of beans unless you can apply them using the following approach.

There are three cardinal axioms that every good training philosophy must adhere to to be effective:

• Consistency: Optimal gains are made by repeatedly applying the training stimulus regularly and frequently. Every workout makes a small deposit into your fitness bank account. Only with consistency will those small deposits add up to enough money in the fitness bank account to allow you to go on a wild spending spree during your event without bouncing checks.
• Gradual Progression: Our bodies will respond to training if the training load is gradually increased over weeks to months. They do not respond well to sudden jumps in training load. This principle is often called progressive overload.
• Modulation: The training load must not only gradually progress but also modulate between hard and easy. Lower loads must follow heavy loads so the body has time to recover and make the adaptations that result in increased fitness.