For years I fell into the trap: thinking that asphalt was enemy territory. I'm a mountain man, you know. As if crossing the white line on the hard shoulder, stepping on that tarmac surface, was betraying my passion for the mountains. But when the cold winter arrives, that rain that makes you stay at home... , that's when you can go out to another terrain, train, and of course, sign up for a half marathon to keep the tension and a challenge close. Out of curiosity. Out of inertia. For not losing your pulse. This can change the way you train forever.

Because a half marathon - that classic 21.097 km, that intermediate test between speed and endurance - can become a powerful tool for any trail runner who wants to perform better, not only on the flats, but also on the summits.

Running on asphalt to perform better in the mountains. Why include a half marathon in your season?

The beauty of trail running is its unpredictability: every race is different, every trail changes depending on the rain, the wind, the gradient or the mood of the marmots. But among so much variability, there is one thing that always counts: your engine.

And asphalt, that imaginary enemy, allows you to tune it like a metronome. It forces you to keep a rhythm, to maintain an efficient stride, to listen to your body without distractions.

Many trail runners include a HALF MARATHON as part of their winter preparation to keep up the pace and work on base speed. They do this for a number of reasons, but here are three that make perfect sense:

1. Build a solid aerobic base

In winter, when the big mountain races take a break, the body asks for volume. It's time to get back to basics: long runs at conversational paces, strength work, slowly but surely, and a few sessions to remind you that you can still run with a spark. And that's where the half marathon comes in: a challenge that requires perseverance, economy and a head. Running 21 kilometres on asphalt, with no change of pace or topographical excuses, is a lesson in humility. It's like putting bricks on your house without it falling apart on the first technical descent, like reinforcing the foundations so that you can then play at heights without fear.

2. You increase your critical speed

You don't need to be fast to run ultras, but it helps. Having a good critical speed doesn't mean you'll fly through a vertical kilometre, but it does mean you'll save energy on every false flat, every forest trail, every stretch where you can really run. Raising your physiological ceiling makes any pace below it easier, more sustainable. And the half marathon is perfect for working right at that threshold where your body gets serious, where everything starts to burn but you can still maintain control. It's that edge where the good runners train, the ones who not only endure, but push forward with conviction.

3. You train your head, not just your legs

On trail, the environment rules. On asphalt, you rule. There are no rocks to slow you down, no hills to force you to walk. Just you, the clock and the endless straight line. And there's a point to that too. It's a brutally honest way of facing your own pace, your ability to sustain the effort when no one is watching, when you can't hide behind the scenery. Running a half forces you to be present, to negotiate each kilometre, to measure yourself without filters. It is a pulse with yourself that is worth more than many hills because there are no excuses: what you give is what you are.

How to fit asphalt into your trail calendar

The key is not to see it as a betrayal, but as a complementary tool. 

It's not about becoming a road runner. It's about becoming a better mountain runner. It's about getting back on the trail with a more efficient stride, a deeper endurance, a more focused head.

Because when you climb an endless hill at the 42nd kilometre of an ultra, what counts is not whether you came from asphalt or rock. It's whether you've trained well. If your engine holds up. If your body has been challenged from different angles. And here, the half marathon can make all the difference.

This scheme may work for you if your heart is in the mountains, but you don't mind stepping into the city from time to time:

Winter (December to March): construction + half marathon

• Volume, gym, controlled slopes.
• Aim for an average for February or March. Flat, fast, well organised.

Spring (April to June): medium + technical trails

• 20-30 km races, first slopes.
• You return to the bush with rhythm and sparkle.

Summer (July to September): altitude + long distances

• The great crossings, the personal challenges, the ultras.

Autumn (October-November): active break + optional test

• Another half, if you feel like it, without pressure. Or rest, if the body asks for it.