Preparing a Half Marathon — Plan Length, Volume, Threshold Work, Long Runs and Taper

The half marathon sits between the races decided by speed and the race decided by fuel. It is long enough that aerobic volume and durability matter, and short enough that most runners finish before their glycogen runs out — so it is run much closer to the lactate threshold than a marathon. A half-marathon plan is therefore built around the threshold: more threshold work than a marathon plan, shorter long runs, and race-pace sessions that are hard rather than long.

This document describes how a half-marathon preparation is built — length, volume, the key sessions, the long run and the taper. It complements the general endurance document, which covers zones, polarized training and strength for runners.

What the Half Marathon Demands

Pace sits close to the threshold

Recreational runners race the half marathon at roughly 80% of VO2max, at a speed close to the one where blood lactate reaches about 4 mmol/L; well-trained runners finishing in 75–90 minutes run it very near their lactate threshold — the fastest pace that can be held for about an hour. Runners who need two hours or more run a little below it. The race feels comfortably hard from the start and genuinely hard over the last five kilometres.

Threshold is the main lever

The speed at the threshold predicts half-marathon time better than VO2max does. In one large group of runners, the speed at the second threshold, peak treadmill speed and running experience together explained almost all of the differences in finish time, and training volume was strongly related to it too. Raising the threshold pace is the most direct way to run faster; VO2max and economy still matter, but the week is organised around threshold sessions.

Fuel matters less, but not nothing

Runners finishing in under about 75 minutes rarely need carbohydrate during the race. Multi-day carbohydrate loading raised muscle glycogen but did not improve a 21 km run. For runners out for 1:30–2:30, a moderate intake during the race helps, and it is worth rehearsing in long runs.

Before the Block: Readiness and Length

Readiness

The block should start from consistent running three or more days a week and a long run of about 45–60 minutes completed comfortably. Runners covering less than about 15 km a week, or running slower than about 6:00 per kilometre, tended to get injured more often in half-marathon preparation, so very low volume is better raised in a general base phase first.

How long the preparation lasts

Situation	Typical length
First half marathon, from a 5K–10K base	12–16 weeks
Experienced runner with a current base	8–12 weeks
Low current volume, returning after a break, or 50+	14–18 weeks

As for any race, the plan is built backwards from race day: the taper ends on the race and the base fills the time before the specific weeks. A plan that would end weeks before the race extends its base instead.

Frequency

Three runs a week is enough to finish; four or five gives room for a threshold session, an easy run with strides and a long run without stacking hard days.

Weekly Volume

Runners averaging more than about 32 km a week finished their half marathon around four minutes faster than those at 20–32 km, without more injuries.

Goal	Peak km per week	Roughly, hours per week
Finish a first half marathon	25–35	3–4
2:00–2:15	30–45	3.5–4.5
1:45–2:00	40–55	4–5
1:30–1:45	50–70	4.5–6
Sub-1:30	65–90	5.5–7.5

These are coaching-practice peaks, not starting points:

• Start from the runner's own recent volume, measured over the weeks they actually ran.
• In half-marathon runners, weekly increases of 20–60% raised the short-term injury risk compared with increases under 20%. Building about 10% per week between loading weeks stays well clear of that.
• A lighter week every third or fourth week cuts volume by 20–30% and keeps a shorter long run.
• Reach the peak two to four weeks before the race and hold it for about two weeks.

The Key Sessions

Threshold work — once or twice a week

Form	Example	Progression
Cruise intervals	4–6 × 5–8 min at threshold, 1–2 min jog	from 20 to about 40 min of work
Tempo run	20–30 min continuous at threshold	toward 30–40 min, or split in two blocks

Threshold pace is about the pace a runner could hold for an hour; for runners slower than about 1:40 it is a little faster than half-marathon pace. Two threshold sessions a week suit experienced runners in the build phase; one is enough for most.

Half-marathon-pace work — in the last 6–8 weeks

Weeks before the race	Example
8–6	3 × 3 km at goal pace, 2–3 min jog
5–4	2 × 5 km at goal pace, 3 min jog
3	10–12 km at goal pace inside a 16–18 km run

Goal pace comes from a recent 10K: the standard conversion (about 2.2 times the 10K time) works reasonably well up to the half marathon, unlike the marathon. The race-pace sessions check it: if 2 × 5 km at goal pace is not controlled three to four weeks out, the goal is too fast.

VO2max work — sparing

Short intervals (5–6 × 3 minutes, or 8–10 × 1 minute) once every week or two in the build phase help faster runners. Slower runners gain more from threshold work and volume.

Strides

6–10 × 20 seconds, relaxed and fast with full recovery, on one or two easy days a week. Cheap, and they keep the stride economical at race pace.

The Long Run

• Runners whose longest run exceeded the race distance finished about four minutes faster, and slowed less in the last part of the race, than those whose longest run was 15–21 km.
• Builds to about 90–120 minutes: 16–22 km for most runners, reaching or slightly passing the race distance (22–24 km) when it fits in that time; slower runners cap it by time rather than distance.
• Adds about 10 minutes every week or two; shortened, not dropped, in lighter weeks.
• In the last six weeks, some long runs finish with 3–8 km at goal pace or a steady progression.
• The longest long run falls two to three weeks before the race.
• Keep the day before and the day after easy, and heavy lower-body strength at least 48 hours away.

Distribution and Structure

• Most of the running time easy; threshold the largest share of the rest.
• At most two quality sessions a week besides the long run, never on consecutive days. On three or four days a week: one quality session and the long run.

Phase	Share of the block	Focus
Base	first third	easy volume, long run, strides, one threshold session
Build	middle third	threshold progression, occasional VO2max, long run toward its peak
Specific	last 4–6 weeks before the taper	goal-pace sessions, threshold kept, long runs with goal-pace finishes
Taper	last 7–14 days	volume cut, intensity kept

The Taper

• One to two weeks. The best-supported tapers across endurance sports last about two weeks and cut volume by 41–60% progressively, keeping intensity and frequency. Shorter tapers of about a week are common for the half; in one small study a one-week taper before a half marathon reduced muscle damage without measurably changing the time, while a one-week taper with intervals kept improved 5 km performance by about 3%.
• Keep a short threshold or goal-pace session and the number of runs; the last hard session is four to six days before the race, and race week has strides and one short goal-pace touch.

Fuelling

• Under about 75 minutes: no carbohydrate needed during the race; a normal carbohydrate-rich meal the day before and breakfast two to three hours before the start.
• 75 minutes to 2:30: 30–60 g of carbohydrate per hour, rehearsed in long runs.
• No multi-day carbohydrate loading is needed; a carbohydrate-rich day before is enough.
• Avoid both large fluid losses and drinking well beyond thirst.

Pacing the Race

Even pace, with the first kilometre or two held back. The middle of the race should feel controlled; the effort rises in the last five kilometres at the same pace, and that is where the race is decided.

Strength Training and the Hybrid Athlete

• Heavy strength work with plyometrics improves running economy by about 2–8% and short time trials by 2–4%, without adding body mass.
• Two strength sessions a week in base and build, one in the specific weeks, none or a very light one in race week.
• Heavy lower-body sessions go after a quality run, at least three hours later, or on an easy day — never the day before the long run or a threshold session.
• Lighter strength weeks coincide with lighter running weeks.

Masters Runners (45 and over)

• Half-marathon performance changes little until about 50 and declines by a few percent per decade between 50 and 70; the response to training is preserved.
• Physical performance recovers after hard sessions about as fast as in younger runners, but fatigue and soreness are felt longer: two quality sessions a week at most, with easy days between them, and a lighter week every third week.
• Threshold work is well tolerated; very short, very fast intervals carry more injury risk and give less.
• Strength training stays a priority, with fewer hard sets and slower progressions.
• A longer preparation (14–18 weeks) allows more gradual volume increases.

Common Mistakes

• Running threshold sessions too fast, turning them into VO2max sessions.
• Too few threshold sessions and too many hard intervals.
• Long runs that are too long or too fast to recover from in a week with two quality sessions.
• No goal-pace practice, so the race pace is a guess.
• A goal set from a 5K without checking it in race-pace sessions.

Key Takeaways

1. The half marathon is a threshold race: build the week around one or two threshold sessions.
2. Long runs of 90–120 minutes, reaching or passing the race distance when that fits, capped by time for slower runners.
3. Goal-pace work in the last 6–8 weeks, from 3 × 3 km to 10–12 km.
4. Build volume about 10% per week between loading weeks, avoid jumps of 20% or more, and use a lighter week every third or fourth.
5. Taper one to two weeks, cutting volume progressively and keeping intensity.
6. Fuel 30–60 g of carbohydrate per hour only if the race lasts more than about 75 minutes.