Trail vs road running: how training changes

Trail running vs road running training comes down to one shift: on the road you train by pace and distance; on the trail you train by time, effort and elevation. Same engine, very different demands on your legs.

Signing up for your first trail race? Here’s what really changes: how you measure training, how to compare races, when to walk, how to prepare your quads for descents, and how to eat when the day gets long.

Why pace stops working on trails

On a flat road, pace is a reliable proxy for effort. On a trail, the same pace can be an easy jog on a forest road or an all-out effort on a rocky climb. In a classic treadmill study, the energy cost of running was about 3.4 J per kilogram per meter on the level and about 18.9 J/kg/m at a +45% grade, more than five times higher (Minetti et al., 2002). Add roots, rocks, mud, heat and altitude, and your watch’s pace becomes noise. Trail runners lean on three other measures:

• Time: a long run of 3 hours, not 30 km.
• Effort: heart-rate zones or perceived exertion (how hard it feels, from 1 to 10).
• Elevation gain: meters climbed per run and per week, written D+ by trail runners.

Train by time or distance? Time, almost always

Training by time means your sessions describe how long and how hard, not how far: “75 minutes easy in zone 2, climbs hiked” rather than “14 km at 5:20.” Two runners on the same climb cover very different distances in an hour, but get a similar stimulus at the same effort.

• Easy runs stay easy by heart rate or breathing, even if you walk the steep parts.
• Long runs are counted in hours and grow by time on feet. For an ultra, they’re the backbone of the plan.
• Quality sessions use effort targets: hill repeats, or a “hilly threshold” run at threshold effort over rolling terrain.

Not sure where zone 2 sits for you? Start with our guide to zone 2 running and easy effort.

Kilometer-effort: compare trail races fairly

A 30 km trail with 1,500 m of climbing is not a 30 km race. The International Trail Running Association (ITRA) uses a simple conversion called km-effort: every kilometer counts as 1, and every 100 m of elevation gain counts as 1 more. So km-effort = distance in km + D+ ÷ 100.

Km-effort is a rough guide: it ignores descent, terrain and altitude. But it explains why a 45 km-effort trail feels closer to a road marathon than to a 30 km run, and it’s a sensible basis for sizing your preparation and your long runs.

Uphill: when hiking beats running

Walking up a steep trail is not giving up: it’s often the faster, cheaper option. Researchers at the University of Colorado had mountain runners walk and run up slopes from 9° to 39° at the same vertical speed. Walking cost less energy than running at every angle except the shallowest, and on slopes steeper than about 16° (roughly a 28% grade) walking saved energy (Giovanelli et al., 2016). The energy cost per meter climbed was lowest across a broad band of about 20° to 35°.

Power hiking is a skill to train:

• Short, quick steps, hips forward, hands on your thighs on the steepest pitches.
• In long runs, hike every climb above a set steepness, at a steady effort.
• Poles: in a 2023 study, poles reduced the force on the feet during steep uphill walking without changing metabolic cost (Giovanelli et al., 2023). In other words, they “save the legs.” Train with them before race day if your race allows them.

For elevation gain training, use long hills, repeated short climbs, stairs or a steep treadmill. Track your weekly D+ like road runners track kilometers, and build it gradually toward your race’s climbing density.

Downhill: the part road runners underestimate

Running downhill is mostly braking. Your quads lengthen while they contract (eccentric work), which damages muscle fibers far more than flat running. A 2020 review in Sports Medicine describes strength losses lasting up to 4 to 5 days after downhill running, with soreness peaking 24 to 48 hours later (Bontemps et al., 2020).

The good news: muscles adapt. The same review concludes that prior exposure to downhill running is the most effective way to limit this damage, that short, regular downhill sessions build tolerance, and that the protection fades after a few weeks without eccentric work. Build it progressively.

• Add a few minutes of controlled descending to long runs, then lengthen it week by week.
• Short, quick steps, eyes a few meters ahead, arms out for balance.
• Leg strength (step-downs, lunges, calf raises) once or twice a week.

What a trail training week looks like

Here’s how a week can shift for an intermediate runner moving from a road half marathon to a 30 to 50 km trail. It illustrates the structure; it’s not a prescription.

The long run gets longer and climbs. Weekend runs are stacked (back-to-back) to train on tired legs, which matters most for ultras. Speed work moves onto hills, though one faster session still pays off: most trail races have runnable stretches.

Fueling: you’ll be out there longer

Trail races take longer than road races of the same distance, so eating becomes part of training. For ultras, the International Society of Sports Nutrition suggests roughly 150 to 400 kcal per hour, with 30 to 50 g of carbohydrate and 450 to 750 ml of fluid per hour, adjusted to conditions (Tiller et al., 2019). For efforts of 2.5 hours or more, broader sports nutrition guidance associates intakes up to 90 g of carbohydrate per hour with better performance (Thomas et al., 2016).

The ISSN also supports progressive gut training: practice eating on long runs, at race effort, with your race-day foods. Eat on a schedule, every hour at the latest, rather than when you feel hungry.

Taper and race week

A meta-analysis found the best results with about two weeks of taper, cutting volume by 41 to 60% while keeping intensity and frequency (Bosquet et al., 2007). Keep a few short climbs and easy descents, but skip long, punishing descents in the final days: downhill soreness takes days to clear.

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