Cardiff Half Marathon
training plan
An adaptive half marathon plan for a flat course on road, run in cool October conditions, built around the three things Cardiff actually asks of you: a flat, fast profile, exposed wind and a mass field. Twelve weeks written two at a time, from what you actually did in the two weeks before, and rewritten the moment you travel, get ill or something starts hurting.
This page describes the race and what its course, climate and date ask of a build. On Pro, the plan itself is written for you, from your experience, your weekly hours and your date, so two athletes entered in this race get different plans.
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Three demands, three answers
A generic 12-week half marathon plan gets you to the start line. It has no idea about a flat, fast profile, exposed wind or a mass field.
On the ground, Cardiff is a flat course on road. It is usually held in October, when conditions are usually cool, which is good racing weather but means a cold twenty minutes standing about beforehand. So over a half marathon, pacing discipline decides your day, and the weather is more likely to help you than to hurt you. There will be tens of thousands starters out there with you.
- Profile
- Flat · road
- Usual conditions
- October · cool
- Race season
- Fall, northern hemisphere
- Field
- Large · tens of thousands
Flat and fast means nowhere to hide
A flat course is where people chase a time, which is exactly why it punishes an optimistic first hour. There is no terrain to break the rhythm and no hill to excuse a slow split. It is the same pace, repeated, for the whole distance.
Long blocks at goal pace inside the long session, and a taper built to arrive sharp as well as rested. A pace check tells you whether your recent training supports the number you typed in.
The wind sets your pace for you
Exposed sections turn a steady effort into a fight. Chasing a pace into a headwind spends energy you will want later; sitting up in a tailwind gives away free speed.
Sessions run to effort in exposed conditions, so on Cardiff you already know what the right effort feels like when the number on the watch is lying to you.
The first miles belong to the crowd
A field this size means corrals, a start that takes minutes to clear, and an opening section run at whatever pace the people around you have chosen. Weaving costs more than it looks like it does.
Race-week guidance for a crowded start and an opening section paced deliberately conservatively, so the time you give away early on Cardiff is time you get back later.
Getting in, and getting to the line
Adaptlete has no involvement in entry, allocation or ballots for any race. This is what the format asks of your planning.
First come, first served
Places usually go on general sale and disappear on a timetable rather than a draw, so the date you can control is the one you start on. Twelve weeks back from October puts the first week in late July.
Large field
A large field means a start pen, a gun time that is not your chip time, and a first mile you do not control, and on flat ground the first few miles are run at whatever pace the people around you have chosen. Over a half marathon, that is a long time to be running somebody else's race.
Road
Road, which is the easy part to train for and the easy part to get wrong: the same shoes, the same socks and the same drink you intend to race in, used often enough that race morning contains no first times. The peak week puts goal-pace blocks on it, months before October.
You will be training through the northern fall
Work backwards and a twelve-week block for an October race opens around late July, running July through to October. That is the northern fall, and it is the half of the job most plans never mention. The evenings close in through the middle of the block, which is exactly when the sessions get long. The clocks go back, the first properly cold morning arrives, and the last third is run in the dark on both ends of the day. And the last block lands in October, with flat ground, cool conditions and a large field waiting at the end of it.
So the plan front-loads the sessions that need daylight and moves the ones that do not into the week, rather than quietly assuming you will find three spare hours of light in November. Whatever the season takes out of two weeks, the work for a flat, fast profile, exposed wind and a mass field is what the rebuild puts back first.
- Weeks 1-5 July-August early starts and heat; the long sessions move to the cool hours
- Weeks 6-7 August-September the light goes; the sessions that need it come first
- Weeks 8-12 · peak and taper September-October
Months assume Cardiff keeps its usual October slot and that you take the full 12 weeks. Adaptlete builds from the date you enter.
A real week from a Cardiff build
This is the shape of the biggest week in 12: 4-5 runs a week, 5H 18M of training, and one session that matters more than the rest. Two of them are here because of this course and not the distance: goal-pace blocks for the flat profile, and a cold-start rehearsal for conditions that are usually cool. The key session itself is written for a flat, fast profile. For an October race, week 8 lands in September. Your version is written from your hours, your history and how far out you are.
- Every session says what it is for, in plain language
- Intensity you can scan down the week without reading
- Move any session to any day without breaking the block
| Day | Intensity | Session | Distance and duration |
|---|---|---|---|
| MON | Rest | Rest | |
| TUE | Zone 4, threshold | Goal-pace blocks: 3 × 15 min at race pace | 7 mi55' |
| WED | Zone 2, easy | Easy run | 5 mi42' |
| THU | Zone 3, steady | Strength: hips & calves | 40' |
| FRI | Zone 1, recovery | Cold-start rehearsal: race effort inside the first ten minutes, from cold | 4 mi34' |
| SAT | Zone 3, steady | Long run: a long block at goal pace | 14 mi1H45 |
| SUN | Zone 2, easy | Easy run + strides | 5 mi42' |
Something will go wrong.
That is the part we built for.
Nobody finishes a twelve-week build without missing a week, and July through to October is a long time to stay lucky. The plans that fail are the ones that carry on as if nothing happened.
A work trip in week 7
Hotel treadmill, nothing else? Those days get rewritten around it.
Flu in August
The block rebuilds and ramps you back. Nothing is deleted.
A niggle at week 8
Loading comes off it, the rest of your week stays. And go see someone.
Questions people actually search
How many weeks do I need to train for Cardiff Half Marathon?
Twelve weeks is the usual build for a half marathon like Cardiff, at 4-5 runs a week. Counted back from an October race that opens the block around late July and runs it July through to October. Coming from a lower base, give yourself longer. With fewer weeks than that the plan compresses. It builds what it can from where you are, protects the work for a flat, fast profile, exposed wind and a mass field first, and tells you plainly what it had to leave out.
When should I start training for Cardiff Half Marathon?
Cardiff is usually held in October, and the next edition an athlete could realistically build for is Fall 2027. Count back twelve weeks from whatever date you enter and the block opens around late July, running July through to October. Adaptlete builds backwards from your date, so the whole half marathon plan lines itself up the moment the date is confirmed. Entry runs on a separate clock (places here are first come, first served), and the training deadline is the one you control.
Is Cardiff Half Marathon really as fast as people say?
A flat course on road, and in October conditions are usually cool, which is good racing weather but means a cold twenty minutes standing about beforehand. So pacing discipline decides your day, and the weather is more likely to help you than to hurt you. That combination is what the twelve weeks are built around: a flat, fast profile, exposed wind and a mass field. The half marathon on its own would give you a completely different plan.
Is Cardiff Half Marathon a good course for a personal best?
It is a fast profile, which is why so many people target it and why so many go out too hard. The plan works backwards from your goal pace, rehearses it inside the long session, and tells you plainly if your recent sessions do not support it. Here that sits inside twelve weeks on flat road for an October race, alongside exposed wind and a mass field.
How do I train for the wind at Cardiff Half Marathon?
You cannot rehearse a headwind to order, so the plan trains the thing wind exposes: holding effort when the pace number stops making sense. On flat road in October that means sessions run to effort rather than to pace, and a race plan that spends nothing chasing a split into a block headwind. Over twelve weeks it is the same discipline a flat, fast profile, exposed wind and a mass field all ask for.
What is the start like at Cardiff Half Marathon?
A large field means a start pen, a gun time that is not your chip time, and a first mile you do not control. With tens of thousands starters on flat road, the opening miles are the most common place a good half marathon build gets spent in ten minutes. The plan rehearses the first section at goal effort inside the long session, so the pace you hold in October is one your legs recognize and the crowd did not choose. It keeps the work for a flat, fast profile, exposed wind and a mass field in the block while it does it.
Is this an official Cardiff Half Marathon training plan?
No. Adaptlete is an independent training-plan service with no affiliation to the organizers of Cardiff Half Marathon, and none is implied. We name the race because the plan is built around what its course, its format and its date ask of you.