How to prepare for a half marathon

Prerequisite: what you need before you start

A half-marathon plan assumes you already run regularly: at least three times a week, around 20 to 25 km weekly, and a longer run of 8 to 10 km without suffering. If you're not there yet, spend four to six weeks building that base before starting the plan. Starting from too little is the recipe for getting hurt in the build phase.

It also helps to have a recent 10K race (or a timed run). It serves as a reference for the plan's paces and for the time goal — and avoids the trap of training for a time that doesn't match where you are.

The four phases of the cycle

Base (4 to 6 weeks): volume rises slowly, almost everything at an easy pace, long run of 10 to 13 km. The goal is structural endurance: tendons, bones and muscles handling more kilometers. Build (4 to 6 weeks): tempo runs of 25 to 40 minutes and 1,000 m intervals come in; the long run reaches 15–17 km and weekly volume peaks (35 to 55 km for most).

Peak (2 to 3 weeks): long runs of 17 to 19 km, some with race-pace segments at the end, and the distance-specific workout — for example, 3 × 3 km at target pace. Taper (2 weeks): volume drops 30 to 40%, intensity stays, and you arrive rested without losing fitness. The taper is where many people "overtrain out of anxiety" and arrive tired.

The long run: how much and how

You don't need to run 21 km before the race. A long run of 17 to 19 km, done two or three weeks out at a comfortable pace, is enough: on the day, adrenaline, the taper and the crowd cover the rest. Running the full distance in training costs a week of recovery and brings no proportional gain.

The long run grows by at most 2 km a week and never exceeds about a third of weekly volume. Every three or four weeks, it steps back along with the down week. The pace is conversational: 45 to 75 seconds per kilometer slower than race pace. A race-pace long run is a classic mistake — it becomes a race every week and the body doesn't recover.

Nutrition and hydration on long runs

From 75 to 90 minutes of running, the body benefits from carbohydrate during the workout: 30 to 60 grams per hour as gel, chews or sports drink. Test on long runs what you'll use in the race — the stomach trains too. Hydration depends on heat and sweat; a practical reference is drinking small amounts every 15 to 20 minutes.

In the two days before the race, increase the share of carbohydrate in your meals without increasing the total amount of food. It's not the time to eat more; it's the time to change what you eat.

Strategy for the 21 km

Split the race in three: the first 7 km slightly slower than target (5 to 8 seconds per kilometer), the middle 7 at target, the last 7 with whatever's left. The half is a race of patience: those who start at the right pace pass dozens of people in the last 5 km.

Set an A goal (the time you want if everything goes right), a B goal (realistic for a normal day) and a C goal (finishing well). That way, heat, wind or a bad night's sleep don't turn the race into a failure — they only change which goal is in play.

How PaceOn helps

The plan is built up to the race date, with the four phases distributed over the available time and a clear warning if the window is too short for the long run to reach the ideal. Every long run has its distance and pace range computed from your runs, and the race strategy is generated with pace by segment and A, B and C goals.