Éric Lacroix: The French Author Who Built the Foundations of Modern Trail Training
If there's one French-language author every serious trail runner should know, it's him. Éric Lacroix is a former international mountain runner, head coach of multiple UTMB winners, and author of a series of books that have become reference works in the trail community: Trail ! volumes 1 and 2, and their merged re-edition, Trail ! Le manuel ultime. His trademark: turning sport science into training tools you can actually use, without sacrificing rigor.
This article offers a profile of the man, a review of his books, and a few takeaways to plug his methodology into your own practice.
A rare profile in the French training scene
Éric Lacroix is a PE professor (agrégé) and director of sports services at the University of La Réunion. But behind the academic title sits a sporting and technical résumé that's hard to match in the francophone trail world.
His background
- Elite runner: member of the French national mountain running team from 1991 to 1995, marathon PB of 2h18'
- National off-track coach (Level 3) for the French Athletics Federation
- National head coach of the Asics trail team since 2012
- Personal coach of major athletes including Xavier Thevenard (three-time UTMB winner), Thomas Lorblanchet, Andréa Huser, Diego Pazos…
This dual identity — academic researcher and field coach — explains the tone of his books: scientific yet grounded, rooted in the practice of athletes he knows personally.
"A trail isn't a sequence of workouts; it's a project. And every project must be planned."
Why his books are reference works
In the early 2000s, trail running was exploding in France, but structured training resources were scarce: a few magazine articles, lots of trial-and-error, no coherent method. Lacroix was one of the first to formalize a complete framework, weaving together:
- endurance physiology (energy systems, thresholds, fundamental endurance);
- long-cycle planning (preparing a goal race over 6 to 12 months);
- trail-specific demands: vertical gain/loss, downhill skill, ultra-distance fueling and mental management;
- individualization: not a template plan, but a logic for adapting load to a runner's profile.
His books are illustrated by Matthieu Forichon, the cartoonist behind the popular humorous trail series Des Bosses et des Bulles. The science-meets-humor combination makes them far more readable than the average training textbook.
His trail bibliography
1. Trail ! Le manuel ultime — Observer, comprendre, s'entraîner (Amphora, latest edition)
This is the book to buy first if you're new to Lacroix's work. The edition combines volumes 1 and 2 of the original series in a single book, with new chapters on applied neuroscience and modern endurance psychology.
Inside:
- What is trail running? History, formats, specific demands.
- Modeling performance: the determinants of trail success.
- Energy systems and thresholds applied to vertical gain.
- Training methods: vertical VO2max work, long runs, downhills, hill repeats.
- Annual planning, periodization, peak form.
- Mental preparation, neuroscience of long efforts.
- Nutrition, hydration, sleep, recovery.
Note: the book is in French. There is no English edition at the time of writing, but the diagrams, tables and references make it usable for non-native readers with intermediate French.
👉 Order Trail ! Le manuel ultime on Amazon
2. Trail ! Volume 1 — Découvrir, observer et modéliser (Amphora)
The founding volume of the series, published in the early 2010s. Lacroix lays out his core concepts: performance modeling, runner profiles, reading a race through its physiological demands. Still relevant, though most of its content has been folded into the Manuel ultime.
👉 View Trail ! Volume 1 on Amazon
3. Trail ! Volume 2 — Planifier et s'entraîner (Amphora, 2019)
The natural follow-up, this volume gets into the concrete mechanics of programming: how to build a cycle, integrate endurance, intensity and trail-specific work, manage weekly volume and the split between road, trails and vertical. A goldmine for runners who want to graduate from internet plans to a personally tailored program.
👉 View Trail ! Volume 2 on Amazon
4. Guide d'entraînement à l'ultra-trail: Le grand raid (with Robert Chicaud)
An older work, co-written with Robert Chicaud, focused on La Diagonale des Fous in Réunion island — where Lacroix lives and coaches. Highly specific, but still valuable for runners targeting an ultra with extreme vertical and heat.
👉 View the Ultra-Trail Guide on Amazon
Key concepts to take away
For those who don't have time to read everything, here are the core ideas that recur across his books.
1) Trail performance is multifactorial
Lacroix is emphatic: trail can't be reduced to VO2max or lactate threshold. Five major determinants interact:
| Determinant | What it covers |
|---|---|
| Aerobic capacity | VO2max, running economy, fundamental endurance |
| Specific strength | Climbs, descents, ability to absorb negative elevation |
| Energetics | Fat oxidation capacity, in-race nutrition management |
| Mental | Discomfort tolerance, sleep management, decision-making |
| Tactics | Pacing strategy, aid stations, gear management |
A quality training plan addresses all five, not just the first two.
2) Long-cycle planning is non-negotiable
For a major goal (first 100 km, UTMB, Diagonale des Fous…), Lacroix recommends a 6 to 12 month cycle with:
- A broad aerobic base at the start of the cycle (volume, easy running);
- A strength block integrating hill work, strength training and downhill-specific drills;
- A specific block that mirrors the demands of the goal race (long runs, weekend back-to-backs, terrain similar to the event);
- A progressive taper in the final 2 to 3 weeks.
The classic mistake: jumping straight into specific work without building the base.
3) Train the runner, not the plan
This is probably Lacroix's biggest pedagogical contribution. Rather than copy a template, he invites every runner to position themselves on a set of profiles (endurance-leaning, power-leaning, all-rounder…) and adapt load to their strengths and weaknesses.
This logic echoes other modern references in physiology and injury prevention, like Blaise Dubois's Running Clinic: no universal recipe, just principles applied to the individual case.
4) Vertical is its own discipline
A large portion of the books is devoted to the uphill/downhill specificity:
- Climbing: vertical VO2max (V̇am, in m/h) is a more useful indicator than flat VO2max.
- Descending: this is where many races are won or lost. Technique, eccentric quad strength, dedicated downhill sessions.
- Short vs. long hills: different physiological targets — neuromuscular power on one hand, lactic tolerance on the other.
Who are these books for?
| Profile | Relevance |
|---|---|
| Trail beginner | The Manuel ultime can feel dense — start with the introduction and basic planning chapters |
| Intermediate runner | Sweet spot: volumes 1 and 2, or the Manuel ultime, depending on how much structure you need |
| Advanced/elite runner | Modeling tools, periodization, individualized load management |
| Coach / health professional | An essential francophone reference, frequently cited in academic work |
Caveats
It would be incomplete not to mention them:
- The books are dense: 400+ pages with tables, formulas, diagrams. Not couch reading.
- The visuals can feel textbook-like at times — the humorous illustrations don't fully offset the academic register.
- Sport science evolves fast: some recommendations on nutrition or recovery would benefit from updates with the latest publications.
But for plan construction and training philosophy, the content remains highly relevant years after publication.
Conclusion
Éric Lacroix belongs to that generation of francophone coach-researchers who professionalized trail running in France. His books aren't read like a novel — they're studied, returned to, annotated. That's exactly their value: they're tools more than manuals, kept on the shelf during goal-race preparation.
If you only buy one, get the Manuel ultime — it's the most polished version of his thinking.
"A good training plan isn't a calendar. It's a logic of progression that you understand."
Further Reading
- Complete Guide to Trail Running
- UTMB: The World Summit of Trail Running
- Joseph Mestrallet, Data Scientist of Trail Performance
- The Running Clinic — Blaise Dubois's Injury-Free Guide
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