Trail running Training Zones

Running mostly focusses on maintaining a consistent pace and effort over a prolonged period. This is perfect for the aerobic system, which prefers a set intensity over a given time, much like a car being in the same gear on a highway.

Trail, mountain, fell and cross country running are very different beasts though. Uneven footing, hills with varied inclination, descents, terrain differences, jumps, altitude and temperature changes etc. Initially adjusting to, progression and eventually competition requires training to respect these race conditions.

It can also be (“can” because there’s prevention for almost everything) very violent on muscles, joints, bones and the metabolic and nervous systems. A rough 100km ultra could be the equivalent of 10 to 16 hours of continuous gym, running, jumping and a multitude of other movements, while being sleep deprived, somewhat dehydrated and with too much or too little nutrition depending on your progression through aid stations.

A good training programme not only includes preparation for all of the above, but also race specificity – adjusting training load and working on specific aspects more prominent for a given objective. But first, let’s talk fuel ..

Energy sources


For the context of ultra endurance events, I’ll focus on the 2 primary sources for those …


Carbohydrate resources stored in the muscles and the liver. This supply is limited to about 2000kcal, enough to power 90 to 120 minutes of high intensity exercise. If you ever “hit the wall”, then you know what it feels like when this runs out 🙂 Glycogen is thus 4kcal x 500g (1g of glycogen/carbohydrates is equal to 4kcal) for most athletes. The 2000kcal ceiling is for highly trained athletes – most have less.

Used when training intensity is high, high end of the aerobic zone or above.


Fat stores in the body that provide a concentrated source of energy. As intensity decreases, fat becomes a very important fuel source as it spares glycogen as a primary fuel source. We can store up 80 000kcal+ in the body (1g of fat is 9kcal), thus it’s a limitless energy supply. I’ll cover “Fat Adaption” in an upcoming post.

Used at lower intensity exercise, mostly in the aerobic zone.

Training zones


A good training plan incorporates training at various intensities, each very important for adaptions specific to races of varied profiles. Zones are also complimentary (high intensity MUST co-exist with recovery etc.)


Performed at very low intensity and helps to clear out lactate and other metabolic waste from hard workouts. Also very important for aerobic system adaptions and “resetting” the cardio and nervous systems.

Fuel: mostly fat, but also some glycogen


Improves aerobic efficiency – the body’s ability to produce energy in the presence of oxygen. You’d mostly race in this zone.

Fuel: hybrid fat and glycogen, about 50% each when exactly on your Maff zone.

Threshold training

High intensity tempo runs to raise lactate threshold and tolerance. Helps to teach your body to use lactate more efficiently, so it takes longer to build up in your blood.

Fuel: Mostly glycogen, 70%+


Helps the body resist conditions of hypoxia(lack of oxygen) and trains it to maintain a high intensity in the presence of metabolic waste.

Fuel: Mostly glycogen, 90%+

A simple formula for your aerobic zone

An easy and mostly accurate method for finding your aerobic zone is the 180-Formula. It requires training and controlling intensity with a heart rate monitor.

180 – <your_age>

You can measure progress of your aerobic system over time by using the MAF test . A better and more reliable way is having a stress and lactate test performed in a lab.


A few guidelines

Depending on how many days you can train per week, a balanced plan includes all of the above zones, except when you are in taper or recovery. The end goal is to grow efficiency (running economy) in your aerobic zone, but also allow your body to respond well to more intense climbs etc. Be careful with high intensity sessions – they should always be followed by a recovery session.

An example of how this translates to trail


The profile above is for the upcoming TDS® (Sur les Traces des Ducs de Savoie)

The race profile has an average altitude of less than 2000m, but there’s several peaks above 2000m, with most of time at altitude being from 56km to 86km.

Things to watch out for:

  • It starts with a steep climb from km 2 – potential for lactate accumulation right off the bat if that first climb isn’t performed with caution
  • I’d be in high aerobic, but still within threshold zones and dips in anaerobic on most of the climbs
  • Flat sections (there aren’t many 🙂 ) are mid to high end aerobic zones
  • Descents are performed at aerobic or less, sometimes in recovery zone depending on the gradient
  • Most metabolic waste would accumulate on ascents
  • Most muscle damage occur on the descents
  • 15km -> 36km: potential for overreaching and having to do the climb towards 56km with elevated blood lactate levels
  • 56km -> 86km: reduce intensity as heart rate would be slightly higher due to altitude
  • 86km to 105km: critical valley to control fuel for the finish
  • 111km -> finish: let rip in aerobic zone or whatever else is left

One Comment on “Trail running Training Zones

  1. Fabulous description to those who that do not know trail running and even to those who run but can’t put on words those things that happen during long distance races…. ;)))))

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