November 05

TREADMILL TRAINING FOR TRAIL RUNNERS, BY MAYAYO: WHY, WHEN AND HOW.

Posted by on November 5, 2025 in trail running spain | 1 Comment

TREADMILL TRAINING FOR TRAIL RUNNERS, BY MAYAYO

Trail running chases altitude, oxygen debt, and silence, each stride an act of faith toward a summit we cannot yet see. But there are weeks when trails turn to ice, when wind punishes the ridges, or when the only daylight left is the one inside your living room. That is when the treadmill becomes a bridge, a way to keep climbing when the mountains hide.

Far from being a poor substitute for real ground, treadmill training is a scientific precision tool. It can replicate almost every physiological demand of the trail. It can mimic long climbs, sharpen climbing economy, even teach the legs to absorb downhill punishment without breaking. The trick is to know why it works, how to make it work, and when to call it into service.

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WHY TREADMILL TRAINING FOR TRAIL RUNNING.

Beyond physiology, the treadmill offers what outdoor running rarely can: isolation of variables. In the mountains, wind, temperature, surface, and altitude constantly shift. Indoors, you hold everything constant and change only what you choose — speed, slope, or duration. That control is not sterile; it is empowering. It allows micro-adjustments that refine adaptation with surgical precision.

It is also a tool for injury prevention. By modulating incline and cushioning, athletes can maintain aerobic fitness while protecting vulnerable joints. Post-injury return to running often begins here, with incline walking or gentle uphill jogs that offload impact yet challenge the cardiovascular system.

For coaches, treadmill data is gold. Heart rate curves, power outputs (for those using foot pods or tread sensors), and lactate measurements taken in steady indoor conditions produce clean signals — the kind that make training plans evidence-based rather than instinctive.

And finally, the treadmill is an ally of equality. Not every runner lives near mountains; not every schedule allows dawn escapes into the hills. The belt democratizes elevation. It brings the gradient to wherever you are. With it, anyone can build climbing economy in a city basement or during a storm. It turns geography from destiny into detail.

HOW to train

Running indoors offers no scenery to hide behind, so form becomes everything. Uphill, the key is posture — a slight forward lean from the ankles, eyes forward, hips tall, arms driving in rhythm with short, quick strides. This position keeps cadence high and power flowing from glutes rather than overworking the calves. Breathing deep and steady, not gasping, allows sustained aerobic control during long climbs.

Downhill demands the opposite art: relaxation under tension. Knees soft, strides quick, feet landing under the hips rather than in front. The treadmill’s negative slope helps train proprioception without chaos. Over time, these descents teach neuromuscular economy, the ability to absorb impact without losing rhythm.

A good treadmill program layers these patterns through the season. Early winter emphasizes aerobic volume on gentle inclines, refining technique and cadence. Mid-season introduces intensity: threshold climbs at eight to ten percent, or short bursts of maximal aerobic power at steeper grades. As races approach, the belt becomes a stage for specificity — rehearsing the exact climb lengths and gradients expected on race day. After each block, a recovery phase with flat easy runs and light downhill work restores balance.

Strength work pairs naturally with these sessions. Post-uphill, glute and calf exercises reinforce concentric drive. After downhill bouts, eccentric quadriceps drills—slow squats, step-downs, reverse Nordics—cement durability. The treadmill thus integrates seamlessly into a full athletic cycle: run, strengthen, adapt, repeat.

WHEN to use the treadmill

Every training phase offers a different reason to step indoors. During the off-season, when fatigue still lingers from racing, the treadmill becomes a gentle re-entry. Short, low-intensity climbs restore aerobic capacity without joint stress, and mild negative grades keep the quads awake without trauma. These are the quiet weeks of recalibration, when precision replaces bravado.

As base training begins: Treadmill takes a central role. Long continuous climbs of thirty to forty minutes at moderate slopes build the mitochondrial depth that sustains ultras. Because the belt removes environmental noise, you can monitor heart rate drift, cadence, and perceived exertion with surgical clarity. It’s the ideal laboratory for developing efficiency before adding outdoor variables.

The build phase:  Those crucial six to eight weeks before a main race, is where treadmill work earns its glory. Here, you use it for structured intervals: IIRT-style incline progressions to develop climbing power, steady thresholds at eight to ten percent to raise lactate turn-point, and controlled downhills to inoculate muscles against damage. Consistency becomes the religion: same incline, same duration, measurable improvement.

When the specific period arrives: Treadmill sessions turn into race simulations. The grades mirror actual climbs, the durations match key segments of your event. You can even alternate uphill and downhill blocks to rehearse transitions — a signature challenge of mountain racing where the heart must pivot between different demands within minutes. The belt, indifferent and reliable, provides a safe stage for those rehearsals.

During taper, the treadmill’s role fades to maintenance. Short climbs at moderate intensity keep the nervous system alert, but the heavy lifting is over. The goal is not to gain fitness but to preserve rhythm, to keep coordination sharp while fatigue melts away.

And when the snow or darkness returns after the season, the treadmill waits again — the mountain under the roof, ready for another cycle.

 

TREADMILL TRAINING FOR TRAIL RUNNERS:

THE SCIENCE.

TREADMILL FOR TRAIL RUNNING: The invisible slope.

In 1996, Jones and Doust study quantified something runners had intuited: running indoors felt easier. On a treadmill, the lack of wind resistance lightens the metabolic load. They found the magic correction: a 1 % incline equates the energetic cost of outdoor running at the same speed. That single degree of tilt became legend — the invisible slope that turns a machine into a mirror.

For trail runners, this rule has more than cosmetic value. It is the baseline for truthful effort. Set the treadmill to 1 % when running “flat,” and your heart rate, oxygen uptake, and stride dynamics mirror what happens outside. Any steeper incline after that becomes a climb in the true sense — one that taxes the same physiological systems the mountain demands.

That subtle detail allows consistency across seasons. Whether you’re testing thresholds or logging recovery runs, your belt can speak the same language as your GPS watch on the trail. Indoors and outdoors finally share a vocabulary of effort.

The physics of suffering

Alberto Minetti’s 2002 study expanded the map. By measuring the energy cost of running from steep descent to steep ascent, he showed that slope and metabolism dance in extremes. The steeper the uphill, the more explosive the rise in oxygen demand — a ten percent incline can double the energy cost compared to level ground. Descents tell a different story: moderate downhill feels easy, but beyond −10 %, the body pays again, not through breath but through eccentric destruction.

This non-linear truth is what makes treadmill work invaluable. Outdoors, we rarely hold a constant grade for long; terrain changes rhythm and footing interrupts stride. Indoors, you can freeze the slope at 8 %, hold it steady, and live inside that specific metabolic stress for as long as you choose. It becomes a laboratory of suffering: pure, measurable, repeatable.

The same is true for descents. Controlled downhill bouts of two or three minutes at mild negative grades reproduce eccentric load without chaos. Over weeks, these sessions fortify the quads and connective tissue — the difference between floating through the final kilometers of a mountain ultra or shuffling in pain.

Two sports in one bib

Vernillo’s 2017 review made official what every mountain runner’s legs already know: uphill and downhill running activate the body as two distinct disciplines. Ascents are a symphony of concentric contractions — calves, glutes, and hip flexors orchestrated for propulsion. Descents, in contrast, are a ballet of braking, all eccentric control and neuromuscular shock absorption.

On the treadmill, this duality can be separated, studied, and trained in isolation. Uphill sessions demand high cadence and short ground contact; downhill ones teach restraint and proprioceptive awareness even without rocks. In Vernillo’s words, “the muscle-tendon behavior, stride mechanics, and energy cost differ so much that each slope direction deserves specific preparation.”

For the mountain athlete, this means treadmill sessions should not merely imitate flat road workouts with a tilt added for spice. They should be purpose-built to target the muscle groups, energy systems, and coordination patterns of each slope direction. The incline becomes a precision dial — turn it one way to raise aerobic demand, the other to stress mechanical control.

Climbing with science: the IIRT

De Lucas et al  introduced the Incline Incremental Running Test (IIRT) in 2021, they redefined how we measure effort on hills. Instead of speeding up the belt to increase intensity, they held velocity constant and gradually increased incline. The result? Trail runners achieved the same maximal oxygen uptake as in standard tests, but their cardiovascular patterns shifted — slightly lower peak heart rates, higher oxygen pulse, and a smoother rise in lactate.

Translated into training, this means intensity can be driven not only by speed but by gradient — a key insight for mountain athletes whose races demand long, grinding climbs rather than sprints. An IIRT-inspired session — holding a steady pace while raising incline every minute or two — trains the body to deliver power efficiently uphill, teaching it to metabolize effort in the same rhythm that long ascents impose.

It also highlights the psychological dimension of climbing. Unlike flat intervals that end in seconds, incline work stretches perception of time. The treadmill becomes a mental crucible where patience and pacing merge. Learning to settle into discomfort — to “stay” inside an eight or ten percent climb — is the hidden gift of the belt.

THE OUTDOOR PARADOX.

As  Schöffl’s 2021 field research showed, even the best indoor simulation still softens the truth. When trail runners were tested on a 16 % mountain path versus the standard 1 % treadmill, their oxygen uptake remained similar but everything else spiked. Blood lactate rose higher, respiratory exchange ratios climbed, and energy cost per meter increased. The mountain, with its irregular ground and micro-instabilities, demanded more from the same body.

The implication is sobering but liberating. The treadmill is honest within its limits — it delivers controlled, repeatable stress — but to match the metabolic cost of real climbing, you must push the belt harder. Steepen the gradient beyond ten percent, or extend the duration of your climbs, or reduce recovery intervals. What feels “hard” indoors may still be “moderate” when gravity and uneven terrain join the equation outside.

Thus, the treadmill becomes both teacher and liar: precise enough to educate the engine, forgiving enough to need correction later in the wild. Understanding that balance is the hallmark of the experienced mountain runner.

TREADMILL TRAINING FOR TRAIL RUNNERS,   OPINION BY MAYAYO

At its best, treadmill training is not a replacement for mountain time but a conversation with it. Jones taught us to tilt reality by one degree; Minetti revealed how energy costs curve with slope; Vernillo showed us the biomechanical split between ascent and descent; de Lucas proved that incline progression can match the physiology of real climbing; Schöffl reminded us that outdoor hills will always charge interest on top. Together, they give us the blueprint.

True enough, a treadmill cannot reproduce the crunch of gravel underfoot or the horizon rolling away below a ridge. But I do acknowledge its potential to reproduce effort — and effort is one of the mountain’s true languages. Therefore, when I  next find myself trapped indoors, I will strive to see each step on the belt, each incline dialed in, not as an escape from the mountains but a rehearsal for them.

Because the mountain, patient as ever, will wait. And when the day comes to climb it again, the legs I built beneath fluorescent light will answer the call — steady, powerful, ready to translate science back into altitude.

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