The half-marathon is probably the most poorly prepared distance by amateurs. Too short to scare like a marathon. Too long to improvise like a 10K. Result: most amateur runners arrive over-trained in volume, under-prepared in specific pace, and blow up at kilometer 16.
The SAFE PACE episode with Joggeuse and Alessia Zarbo (French half-marathon record holder) confirmed a long-standing intuition: the half is won by precision, not by quantity.
The "shortened marathon plan" mistake
Amateur reflex: take a marathon plan and cut it in half. It's physiologically absurd. The marathon is run 5 to 10% below lactate threshold. The half is run 2 to 5% above. Two different energy worlds.
Zarbo says it clearly: the half is a "threshold" event. The whole plan must be built around threshold development and tolerance. Not around 30 km long runs — which belong in marathon territory.
The architecture of a smart half prep (10 weeks)
The 3 pillars of the prep
- Pillar 1 — Moderate, consistent volume (40-60 km/week). Max 4 sessions per week for a demanding amateur. Consistency beats overload.
- Pillar 2 — 2 quality sessions per week. One threshold (e.g. 4x2 km at half pace), one VO₂max (e.g. 8x400m). The core of progression.
- Pillar 3 — Long run with specific work (max 1h45). E.g. 1h30 with 30 min at half pace at the end. That's where final-stage fatigue is simulated.
Race-day pacing strategy
The half is split in three negative thirds. First third controlled below target pace. Second third exactly at target. Last third progressively faster if sensations allow. The opposite of what 80% of amateurs do.
— Alessia Zarbo, SAFE PACE episode
The typical amateur starts 5 to 10 sec/km too fast over the first 5 km. The cost: an oxygen debt paid dearly between km 14 and 18. The famous "half-marathon wall" isn't physiological — it's strategic.
My race protocol for my athletes in personalized running coaching:
- km 0 to 7: target pace minus 5 sec/km. Absolute discipline.
- km 7 to 14: exactly target pace. Mental lockdown.
- km 14 to 21: target pace plus 0 to 10 sec/km depending on sensations. If the legs respond, let it roll.
Amateur vs strategy: the pace that makes the difference
- Amateur
- Negative split
The details that make 2 minutes of chrono
At this engagement level, "small details" become major levers:
- Pre-race nutrition. 2h before: 100g complex carbs, low fiber. 15 min before: 30g fast carbs.
- Hydration. 500 mL water with electrolytes within 2h pre-race. Single aid station at km 10-12 if hot.
- Warm-up. 15 progressive minutes + 4 strides. The nervous system must be ready at the gun.
- Taper. -30% volume 10 days out, -50% in the last 4 days. Keep intensity, cut volume.
The executive-athlete trap on the half
What I see systematically in the leaders I coach: they build their prep on willpower, not on actual capacity. Three quality sessions a week + 60 km + 55h of work + travel + 6h sleep = guaranteed formula to arrive tired and perform 5% below your level.
The rule I impose: only one quality session per week during high-load professional periods. Less glamorous, but it's what allows you to hold 10 weeks without injury and arrive fresh. Serious amateur performance isn't a courage question — it's a calibration question.