How to Map Out Training for Your First Marathon: A 20-Week Build and a Plan That Fits You
Updated: 1 day ago
Written by Andy Hood · Ultra runner, cancer survivor and Runna ambassador
Updated 7 October 2026 | First published May 2026
This article contains affiliate links that support the blog and my cancer charity work.
To map out training for your first marathon, work back from race day. Most first-time marathon runners need 20 weeks of structured training, built on a base of running three to four times a week comfortably. Increase weekly mileage by no more than 10%, take a step-back week every third or fourth week, peak with a long run of 20 miles (32km), then taper for three weeks. Complete beginners should allow three to six months to build that base first.
Just here for a marathon training plan? I recommend the one that has seen me complete multiple ultras and marathons: Runna. It builds a plan around your race, your current fitness and the days you can run, and I am one of their official ambassadors. My code ANDY2 doubles the free trial to two full weeks of Runna Premium: start your 2-week Runna free trial. Further down I show what a 20-week build looks like, as an example to learn from.
I've tried to be as comprehensive as possible as this maybe your first marathon; the jump links will help you navigate the guide and find the right section.
In This Guide
I am running the London Marathon on Sunday 25 April 2027.
I mention that at the top because it changes how I am writing this. I am about to start a training block myself, alongside roughly 100,000 other people with a place in the 2027 London Double, the first time the race has been run across two days. I will be making the same decisions you are: when to start, how many days a week, what to do when a week falls apart.
I have been running for years: ultras, multi-day events, 170 miles along the South West Coast Path to Land's End, two finishes of the 160km Tour du Mont Blanc. Before my cancer diagnosis in 2021 I was a fairly casual marathon runner with a 3:45 finish to my name. After surgery and chemotherapy something shifted. My PB is now around 3:20, and almost none of that improvement came from running more miles. It came from finally training properly.
This guide to first marathon training is built on what I learned in that gap: the framework, the shape of a 20-week build, the fuelling, the mental side, and what goes wrong in a training block.
How to Map Out Training for Your First Marathon in Six Steps
Mapping out your training means working backwards from race day and fitting the build around your life. It does not mean copying somebody else's table.
Fix your start date. Count back 20 weeks from race day. That Monday is week one.
Check your base. You should be running three to four times a week before the build starts. If you are not, give yourself three to six months first.
Lay out the four phases. Foundation, development, peak and taper.
Set the rate of climb. No more than 10% a week, with a step-back week every third or fourth week.
Mark the peak and the taper. A 20 mile long run three weeks out, then three weeks of tapering.
Get the sessions built around you. Your paces, your training days and the changes when a week goes wrong have to come from your fitness and your life. A printed plan cannot do that.
Each step has its own section below.
What Does a 20-Week Marathon Training Plan Look Like?
A 20-week first marathon build moves through four phases: foundation, development, peak and taper. Weekly mileage rises by no more than 10% at a time, with a step-back week every third or fourth week, peaking at around 41 miles and a 20 mile long run before a three-week taper.
I am going to show you an example, and I will be blunt about what it is. I have no time for printed training plans. Most sites hand you a table and let you believe it was written for you. It was written for nobody. Whoever drew it up had never heard of you: not your current fitness, not your goal, not which days you can run, how you recover, or what your legs did last winter. So do not print this one and stick it on the fridge either.
I am showing it because the shape of a marathon build is worth understanding, and a table is the quickest way to see it. It is what I would sketch on the back of an envelope if you asked me over coffee. Learn the pattern, then read the section after it. The gap between an example like this and a plan built for you is bigger than most people realise, and I spent years stuck in it.
The example assumes you can already run three to four times a week comfortably. It is built around finishing your first marathon, with no target time. If you are not running that often yet, start with the section on your starting point further down.
An example 20-week build, four runs per week
Week | Phase | Long run | Weekly total | Focus |
1 | Foundation | 6 mi | 19 mi | Establish the routine. All easy. |
2 | Foundation | 7 mi | 20 mi | Consistency over pace. |
3 | Foundation | 8 mi | 22 mi | Getting used to four runs a week. |
4 | Step-back | 6 mi | 16 mi | Absorb the load. Do not skip it. |
5 | Foundation | 9 mi | 24 mi | Long run approaching double figures. |
6 | Development | 10 mi | 26 mi | First double figure long run. |
7 | Development | 11 mi | 28 mi | Begin practising in-run fuelling. |
8 | Step-back | 8 mi | 21 mi | Recovery week. Sleep. |
9 | Development | 12 mi | 30 mi | Add one steady effort session. |
10 | Development | 13 mi | 32 mi | Half marathon distance reached. |
11 | Development | 14 mi | 34 mi | Fuel from 20 minutes onwards. |
12 | Step-back | 10 mi | 25 mi | Physio check if anything niggles. |
13 | Peak | 15 mi | 35 mi | Rehearse race morning breakfast. |
14 | Peak | 17 mi | 37 mi | Full race day kit rehearsal. |
15 | Step-back | 13 mi | 28 mi | Recover before the biggest weeks. |
16 | Peak | 18 mi | 39 mi | Nutrition strategy fully settled. |
17 | Peak | 20 mi | 41 mi | Biggest week. Longest run. |
18 | Taper | 14 mi | 31 mi | Volume drops, intensity stays. |
19 | Taper | 10 mi | 22 mi | Legs will feel strange. Trust it. |
20 | Race week | Race day | ~12 mi + race | Sleep, carbs, patience. |
How the shape scales
Starting from a different base. Scale the numbers but keep the shape. If 20 miles is already a comfortable week, the example fits as drawn. If it is not, take every figure down proportionally and hold the pattern.
Only 16 weeks to go. Start at week 5, which assumes a 9 mile long run is already comfortable, and run through to the finish. Do not compress the taper and do not remove the step-back weeks. Those are the two parts people cut first and the two parts that matter most.
Coming out of a step-back week. Pick up from your last building week plus a little, not from the reduced figure. Week 5 builds on week 3, not on week 4.
What a first-timer's week looks like
Four runs a week: one long run and three easy runs. From week 9, one of those easy runs becomes a steady effort session. Add two short strength sessions and one full rest day and you have the whole week.
Day | Session |
Monday | Strength, 20 to 30 minutes |
Tuesday | Easy run |
Wednesday | Strength, 20 to 30 minutes |
Thursday | Easy run, steady effort from week 9 |
Friday | Rest day |
Saturday | Short easy run |
Sunday | Long run |
Any plan worth following has to be flexible enough to fit around your life. Mine never run to schedule. There are weeks when work or family gets in the way, and I move runs around to make them fit. Treat a plan as fixed and you will eventually miss a session, feel like you have failed, miss another, and quietly give up somewhere in February. I have watched that happen to a lot of people. A plan bending is not a plan breaking.
My long run sits on a Saturday, which is fairly unusual. It works for me because it leaves an easy Sunday to loosen off and a clean start to the week. Yours might need to be a Sunday, or a Wednesday, or split across a Friday evening and a Saturday morning if that is what your household allows. It matters far more that the long run has a settled place in your week than which day you give it.
Free Marathon Training Plan or Runna: Which Should You Use?
A free marathon training plan from the internet is a skeleton without the muscle. What it cannot do is set your paces, react to your week, progress from your results, or tell you whether it is working.
Those four things are the difference between finishing and finishing well, and between finishing and getting injured in February.
It cannot set your paces. A printed plan says easy, steady or hard. Those are efforts, not numbers. A plan that does not know your current fitness cannot tell you that your easy pace is 9:40 a mile and not 9:00.
It cannot react. Week 9 lands on a work trip. Your calf tightens on a Tuesday. You sleep badly for a fortnight. The table says 30 miles regardless, because it was printed before any of that happened. Every adjustment is yours to make, and you will be making them while tired, which is when judgement is worst.
It cannot progress from evidence. The numbers were fixed before you ran a single step. If you adapt faster than average you will be undertrained by April. If you adapt more slowly you will be overreaching by week 14. Either way the table carries on as written.
It cannot tell you whether it is working. There is no feedback loop. You find out on race day.
I spent years on plans like this, lifted off websites and printed out. They told me what to do. They never told me how to do it. What moved me on was training that responded to me: paces set from my current fitness, sessions rebuilt when I missed them, and load that adjusted when the data said I was tired, not when I decided to admit it.
Why I train with Runna
When you set up a plan in Runna you tell it your goal race, your target time, your current weekly mileage, the days you can realistically train and the day you want your long run on. It builds a complete progressive plan around all of that, sets the pace for every session from your current fitness, and delivers the workout to your watch with audio guidance as you run. Then it keeps adjusting, reading each run you sync and reshaping the weeks ahead.
When life gets in the way, and it will, you drag and drop the sessions around on the calendar and the week reshapes itself. No guilt, no arithmetic, no wondering whether you have just broken something. That single feature is probably why I have stuck with it for over three years, and my London 2027 plan is being built in it.
Free PDF plan | Runna | |
Personalised to your goal time | No | Yes |
Paces calculated for every session | No | Yes |
Choose your own training days | No | Yes |
Move sessions when life interferes | No | Yes, drag and drop |
Adapts as your fitness changes | No | Yes |
Race specific, including London 2027 | Rarely | Yes |
Guided audio coaching | No | Yes |
Watch sync (Garmin, Apple, Coros, Suunto) | No | Yes |
Runner specific strength sessions | No | Yes |
Cost | Free | Free for 14 days with code ANDY2, then subscription |
I want to be fair to the left hand column. Free plans are not bad, and plenty of people finish marathons on them. They are incomplete. What a personalised plan gives you is a schedule that reflects the runner you are becoming and not the one you were on day one.
I compare the main options, free and paid, in my guide to the best running training plans.
Runna free trial: 2 weeks free with code ANDY2
As a Runna ambassador I can offer a two-week free trial, double the standard seven days. If it is not for you, cancel at least 24 hours before the trial ends. If you do not, the subscription starts automatically.
Two weeks is enough to run a long run, a tempo session, an interval session and a strength session, and to see how it handles a missed day. Which, over 20 weeks, you will have. A fortnight with it will teach you more about your own training than any printed plan off the internet. There is more detail in my article on Runna training plans.
When Should You Start Training for a Marathon?
Take your race date, count back the number of weeks you need, and the Monday you land on is the day your block begins.
Because I am building towards it myself, here are the dates for the 2027 TCS London Marathon, which runs on Saturday 24 and Sunday 25 April 2027. These are for the Sunday race.
Plan length | Training starts | Who it suits |
16 weeks | Monday 4 January 2027 | Experienced runners with recent half marathon fitness |
18 weeks | Monday 21 December 2026 | Runners with a solid, established base |
20 weeks | Monday 7 December 2026 | Most first-time marathon runners |
24 weeks | Monday 9 November 2026 | Anyone building from a low base |
Base building | September to November 2026 | Anyone not yet running three to four times a week |
If you are running on the Saturday, the same start dates work.
If you are training for something else, Manchester, Brighton, Edinburgh, an autumn marathon, a local spring race, the method is identical. Only the dates change.
One thing about that table. A 20-week block starting in early December means you are settled into a routine before January, when everyone else is starting from zero and the gyms are full. That is a head start, and it is the option I would pick if you have the choice. If London is your race, I have written a separate London Marathon training plan.
If your block is still months away, use the time. I have written about what to do in the running off-season and when to start training for London 2027, and there are separate start dates for Brighton and Manchester 2027.
Do You Need to Run a Half Marathon Before a Marathon?
No, you do not need a half marathon finish before you commit to a marathon. You do need a base, and where you are starting from changes how long that base takes to build.
I have never entered a half marathon event as part of a marathon build. Not once. What I have done in every block is run that distance and beyond, several times, as training runs. In the example above the long run reaches 13 miles in week 10 and keeps going. The distance gets covered either way. The medal is optional.
That said, there is nothing stopping you entering a local half on a week where the plan calls for that sort of mileage, and I would encourage it if the idea appeals. It breaks up a long winter block, it gives you a taste of a start line, and it is good practice for the logistics of race morning.
But you must listen to the programme. If that week calls for 13 miles at an easy pace, you go and run 13 easy miles that happen to have a number pinned to your vest. You do not race it.
The moment you find yourself chasing the runner ahead or glancing at your watch to see if you can beat last year, you have turned a steady endurance run into a hard effort your plan did not ask for, and you will pay for it in the two weeks that follow. Enter it, enjoy it, run it easy.
If you are completely new to running
Your first goal is consistency. You need to be running three to four times a week, with some runs reaching 30 to 45 minutes without stopping, before a marathon plan makes any sense at all.
A Couch to 5K programme is a brilliant place to start. Give yourself three to six months here. There is no shame in it, and the runners who get injured or burn out are almost always the ones who skipped this part.
Once 5K is comfortable, my guide to 5K and 10K training covers the next step.
If you are stepping up from a 10K
You have a foundation. You understand effort, you know what the last kilometre of a race feels like, and you have a routine. The biggest change is the time on your feet, which affects everything from how you fuel to how you recover. Do not assume 10K fitness will carry you further without a structured build.
If you are stepping up from a half marathon
This is the most common route and a smart one. You know long runs, you know race nerves. The jump from 13.1 to 26.2 is still a big one, particularly beyond mile 18, where the race begins. Half marathon training does not prepare your body for the final third of a marathon. That has to be built deliberately.
Wherever you are starting, build from where you are today and not from where you would like to be.
Sort your shoes before week one
Go to a specialist running shop and get properly assessed before your block starts. Not a sports chain, a running shop, where someone will watch you run and talk to you about your gait. The right shoe matters over 26.2 miles in a way it does not over 5K, and a shoe that was fine for parkrun can become a problem at 18 miles.
Buy them early, not in week 15. New shoes need 30 to 50 miles of bedding in, and nobody should be breaking in footwear during a taper.
If you can afford two pairs, rotate them. It extends the life of both and varies the stress on your legs slightly from run to run. Replace them somewhere between 400 and 500 miles, which you may well reach across a 20-week block.
What I am running in at the moment is in my running shoe rotation.
What Is the 10% Rule in Running?
The 10% rule: never increase your weekly mileage or training effort by more than 10% from one week to the next.
It sounds too simple to matter. It matters because different parts of your body adapt to running at different speeds. Your cardiovascular system improves relatively quickly. Your muscles, tendons, ligaments and bones take considerably longer. That mismatch is where injuries live: your lungs feel ready for more while your connective tissue is still catching up.
So if you are running 30 miles a week, next week caps out around 33. Not 40. Not 35 because you felt good on Tuesday. 33, then reassess.
Build weeks are followed by recovery weeks. Every third or fourth week, mileage should drop by 20% to 30% to let your body absorb the load before building again. These step-back weeks are not optional and they are not a sign of weakness. They are where the adaptation happens.
Treat it as a rule of thumb. A 2025 study of 5,205 runners in the British Journal of Sports Medicine found no clear link between week-to-week mileage changes and injury. What did predict injury was a single run more than 10% longer than the runner's longest run of the previous 30 days. So use 10% as a ceiling on your weekly total and keep the jumps in your long run small as well. In the example above it climbs by a mile or two at a time.
I have learned this the hard way more than once. The miles that feel easiest to add are always the ones that come back to bite you.
Easy Runs, Rest Days and Strength Training for Marathon Runners
Run about 80% of your weekly miles at an easy, conversational pace, take at least one full rest day a week, and do two short strength sessions. These three sit underneath the mileage, and they are what get you to the start line in one piece.
Easy runs are not junk miles
Around 80% of your weekly mileage should feel easy, at a conversational pace where you could hold a full sentence without gasping. Only 20% should involve hard effort.
Running easy runs too fast is the most common mistake first-time marathon runners make, and it is why so many arrive at week 12 exhausted when they should be fit. If you are not sure what easy feels like, my guide to Zone 2 running covers it properly, and my running pace calculator will turn your goal time into the paces you should be hitting.
Rest days are part of the training
Rest days are part of the training, not a gap in it, and I would put money on that being the line most first-timers find hardest to accept. You do not get stronger while you are running. You get stronger while you recover from running. A rest day is a session. It just happens to be one you spend on the sofa.
Strength training, twice a week
Two sessions of 20 to 30 minutes a week, on your non-running days, will do more for your injury risk than any amount of extra mileage. It is the part of marathon preparation people skip most often and one of the most valuable.
Pick four to six exercises and do two or three sets of each:
Single leg squats
Step ups
Glute bridges
Calf raises
Side planks
You do not need a gym, heavy weights, or any equipment beyond a step and a bit of floor.
The reason it matters is mechanical. Running is a series of single leg landings, somewhere between 40,000 and 50,000 of them for most first-timers, and weak hips and glutes mean your knees and ankles absorb load they were not designed to take. Strength work also improves running economy, which means the same pace costs you less.
Reduce lower body volume in the final two weeks before race day, but do not drop it entirely. I have written a longer article on strength training for runners, with exercises for the gym and for home.
Why Do Your Legs Feel Heavy During Marathon Training?
Heavy legs between weeks four and eight are normal. It is cumulative fatigue, and it means the training is working.
Marathon training puts stresses on your body that most people have never experienced. Knowing what is coming helps you respond sensibly when it arrives.
The early weeks. You may feel surprisingly energetic. The volume is not yet high enough to fatigue you deeply. Enjoy it, but do not treat it as permission to do more.
Weeks four to eight. Cumulative fatigue arrives. Legs feel heavy. You need more sleep. This is where the 10% rule earns its keep.
Long runs beyond 14 miles. Expect soreness in places you have not felt before: hip flexors, glutes, the outside of the knee. Your musculoskeletal system is adapting to sustained effort, and that takes time.
I was talking to my sports physio recently and he made an observation that has stuck with me. The most common point at which he sees first-time marathon runners walk through his door is right around the 17 mile mark. By that stage the stress on tendons, joints and connective tissue has been building for months, and for many runners it is the point where the body finally says enough, if it has not been listened to before then.
If you are approaching that territory and something does not feel right, do not wait and hope. Book in early, before a niggle becomes an injury that costs you the block. I have a monthly sports massage throughout my training to work through tightness and catch anything building. It is one of the best investments you can make.
What If You Miss a Week of Marathon Training?
Repeat the week you missed and do not jump ahead to where the plan says you should be. One missed week across a 20-week block costs you almost nothing. Trying to make up the lost mileage is what causes injuries.
This is the question I am asked most, and the answer is more reassuring than people expect. I have a longer article on what to do when you are behind on marathon training.
This is the short version.
Time missed | What to do |
One week | Repeat that week, or slot back in at the same level, not the next step up. Your fitness has not gone anywhere in seven days. |
Two weeks | Drop back one week and rebuild from there. Do not attempt the long run you would have been on. Your legs lose their tolerance for time on feet faster than your lungs lose fitness. |
Three weeks or more, with ten or more weeks left | Rebuild, starting conservatively, and accept a slightly shorter peak long run. |
Three weeks lost, with six weeks left | Change the goal. Finish comfortably and forget the time, or move to a later race. |
If you are ill
If it is in your chest, or you have a fever, do not run. Running through a chest infection is how people lose months when they could have lost days. A head cold with no fever is usually fine at easy effort, and if you feel worse ten minutes in, go home.
No block goes to plan
I have never once run a block exactly as written. Not for a marathon, not for a hundred miler. Every single one has had weeks knocked out of it.
In every block I am listening to my body and adapting as I go. I do not push through when something hurts. I do not push through when I am properly tired, as opposed to just reluctant. Learning to tell those two apart is most of the skill, because ignoring them is how a niggle becomes six weeks off.
The runners who reach start lines healthy are not the ones whose plans went perfectly. They are the ones who adjusted calmly when they did not.
What to Eat When Training for a Marathon
Eat enough to fuel the training, take on 45 to 60g of carbohydrate an hour on long runs, and do not try to diet during a marathon block.
Get nutrition wrong and the marathon becomes an exercise in survival. Get it right and you cross the line feeling like you ran it and did not just endure it.
A marathon block is not the time to diet
I understand the temptation. You have taken on a big physical challenge, you are more aware of your body than usual, and a lot of people arrive at marathon training hoping to lose weight along the way. But you cannot ask your body to build a marathon and run a deficit at the same time. Something gives, and what gives is usually your recovery, your immune system and eventually your bones.
If you want the science on this, the person I would point you towards is Siân Seccombe, a sports nutritionist who focuses on relative energy deficiency in sport, or REDs. That is what happens when athletes do not take on enough fuel for the training they are doing. She posts about it constantly on Instagram at @siansecc and covers it in detail on her podcast, The Fuelled Runner. Her message never changes: you have to eat.
Underfuelling does not announce itself as underfuelling. It turns up as:
Legs that never recover
Sleep that stops working
A resting heart rate creeping upwards
Illness after illness
A stress fracture in week 14 that ends your race
Most runners who experience it think they are not tough enough. Eat enough. Fuel the work. If your weight shifts a bit across twenty weeks as a by-product of the training, fine, but do not make it the goal while you are asking this much of yourself.
Daily nutrition during a training block
As mileage rises so does your energy requirement. Many first-time marathon runners undereat, which produces fatigue, poor recovery and a higher injury risk.
Carbohydrates are your primary fuel. Rice, pasta, bread, oats, potatoes. Do not fear them.
Before a long run. A carbohydrate rich meal two to three hours beforehand.
After a run. Carbohydrate plus protein within 30 to 45 minutes of finishing.
Protein. Some at every main meal, for repair and adaptation.
Fluids. Drink more water, and add electrolytes on longer sessions.
Iron. If fatigue persists despite good sleep and food, ask your GP about iron, particularly if you are a female runner.
How to fuel during a long run
Your body stores roughly 90 minutes of glycogen at moderate effort. Beyond that you are relying on fat, which is slower to access, plus whatever carbohydrate you take in while running. That is why fuelling on the move matters.
Aim for 45 to 60g of carbohydrate per hour for your first marathon, building towards 60 to 90g per hour as your gut adapts across the block. Start fuelling 20 to 30 minutes into any run longer than 90 minutes, before you feel you need it, and repeat at regular intervals. If you wait until you feel empty, you are already behind.
Those numbers are in line with the published sports nutrition guidance from Burke and colleagues: 30 to 60g an hour for longer events, and up to 90g an hour for anything beyond two and a half hours.
Whatever you plan to use on race day, practise it on every long run. Your gut needs training just as your legs do, and race day is a spectacularly bad time to discover that a particular gel does not agree with you.
What I use
My own kit is settled after years of trial and error.
Precision Fuel & Hydration electrolyte tablets. They handle hydration without interfering with my carbohydrate plan.
Their PF 30 and PF 90 gels. A 2:1 glucose to fructose ratio and a mild taste that still works four hours in.
Infinit :GO FAR drink mix. On longer efforts it combines hydration and a chunk of my carbohydrate target in one bottle.
My own target sits at the top of that 60 to 90g range, but that adaptation took seasons, not weeks. Start conservatively.
If you want to know why gels mix glucose and fructose, I have written up the science of carbs per hour.
Carb loading in the 48 hours before you run is a separate subject, and I have covered it in how to carb up before a marathon or ultra. Read that in the taper, not now.
Marathon Taper: What to Do in the Last Three Weeks
In a marathon taper your weekly mileage drops by about a quarter, then by about half, across the final three weeks, while intensity stays roughly the same. You are not losing fitness. You are shedding accumulated fatigue so that you arrive at the start line fresh.
Almost every runner I speak to struggles with this phase, and the reason is that it feels like going backwards. The legs get heavy when you expect them to feel light. Easy runs feel harder than they did in week 14. Doubt arrives, and with it the urge to squeeze in one more long run as reassurance.
Do not. That instinct has ruined more races than undertraining ever has. The fitness is already banked. Nothing you do in the final three weeks will add to it, and plenty of things could subtract.
What the taper does need is attention to the boring parts:
Sleep more than usual. This is when 17 weeks of work consolidates.
Keep eating properly. Increase your carbohydrate intake across the final two or three days. Do not attempt one enormous pasta meal the night before.
Stay off your feet where you can.
Avoid anything new. No new shoes, no new gels, no first-ever sports massage three days out.
Browse Instagram in April and you will see plenty of posts about taper tantrums. They are real, everyone gets them, and they pass.
How to Pace Your First Marathon on Race Day
Start slower than you want to, fuel exactly as you practised, and if the wall arrives, slow down but keep moving.
By the time you reach the start line the work is done. Race day is about executing what you have practised.
Before the start
At a big city race you will be standing in a start pen for anything up to 90 minutes. Carry a throwaway layer and eat a small second breakfast while you wait.
The first miles
Start slower than you want to. The first few miles will feel easy: the crowd, the adrenaline, the taper freshness. Resist the temptation to bank time. The marathon always takes it back, with interest.
Fuel as practised, not according to how you feel in the moment.
Hitting the wall in a marathon: the mental side
Ask anyone who has run a marathon what the hardest part was and they will tell you it was the head.
Miles 18 to 22 are where first timers most often meet the wall. Glycogen is depleted, you have been running for hours, and the mind starts negotiating hard. It is the voice that asks whether this is worth it, and whether walking would be so bad.
I have run a lot of miles with that voice, and it lies. It is a protective mechanism, not a reliable signal that you cannot continue. Learning to tell the difference between "this is hard and I should slow down slightly" and "I need to stop" is one of the core skills of distance running.
If you hit the wall, slow down and keep moving. Take a gel, walk a minute if you need to, talk to yourself firmly and kindly. The miles are in your legs.
Four things help:
Know your why. Write it down. Running gave me purpose after my cancer diagnosis, and knowing why I run has carried me through my darkest miles. Yours does not need to be dramatic to be powerful. It needs to be yours.
Break it down. At mile 22, do not think about 26. Think about the next lamppost, the next aid station, the next kilometre. Distance running is a long series of small decisions to keep going.
Expect the dark patches. They will come, in training and in the race. Knowing they are coming means you are not shocked when they arrive.
Celebrate the training. Every completed long run is proof your body is adapting. Do not wait for race day to feel proud.
Crossing the line
When you cross that line, the exhaustion, the pride, the slight disbelief that you just ran 26.2 miles, that belongs entirely to you. Nobody can train those miles for you. You ran them.
If you are on the London course in April 2027, I will be somewhere out there on the Sunday, probably going through exactly the same negotiations in the final 10K. See you at the finish.
First Marathon Training FAQs
How do I map out training for my first marathon?
Count back 20 weeks from race day to find your start date, and make sure you are already running three to four times a week. Build weekly mileage by no more than 10% at a time, with a step-back week every third or fourth week. Peak with a 20 mile long run three weeks out, then taper.
How long does it take to train for a first marathon?
Most first-time marathon runners need 20 weeks of structured training, assuming a base of running three to four times a week with some runs of 30 to 45 minutes. Sixteen weeks works for runners with recent half marathon fitness. Complete beginners should allow an additional three to six months to build that base before a marathon plan begins.
How many miles a week should I run?
Most first marathon plans peak somewhere between 35 and 45 miles per week. The figure matters less than the progression: never more than 10% week on week, with a step-back week every third or fourth week. Consistency across months beats any single big week.
What is the longest run before a first marathon?
Twenty miles, about three weeks before race day. In a 20-week build that falls in week 17, and the taper starts straight after. You do not need to run the full 26.2 miles in training.
Can a complete beginner run a marathon?
Yes, with a realistic timeline. Do not jump straight into a 20-week plan from nothing. Spend several months building a consistent running habit first, then move into marathon specific training.
What is the 10% rule?
Never increase weekly mileage or training effort by more than 10% compared with the previous week. Your cardiovascular system adapts faster than your tendons, muscles and bones, and that mismatch is where injuries happen.
How many days a week should I run?
Four is enough for a first marathon, and it is a schedule most people can sustain alongside work and family. That means one long run and three easy runs, with one easy run becoming a steady session from week 9, and three days off running. Five or six days a week is fine for experienced runners but adds injury risk for beginners.
What if I miss a week of training?
Repeat the week you missed and do not jump ahead. One missed week across 20 costs you almost nothing. Trying to make up the lost mileage is what causes injuries.
When should I start fuelling on a long run?
Twenty to 30 minutes into any run over 90 minutes, before you feel you need it. Aim for 45 to 60g of carbohydrate per hour to start, building towards 60 to 90g as your gut adapts. Practise your exact race day strategy on every long run.
How do I know if I am overtraining?
The warning signs are:
Heavy legs that do not recover
A raised resting heart rate
Disrupted sleep
Declining performance
Getting ill more often
Loss of motivation
Any pain that worsens during or after runs
If several appear together the answer is proper rest, not a lighter run.
Should I use a free plan or a training app?
Plenty of people finish marathons on free plans, but those plans are written without knowing you. A personalised app like Runna adds three things a PDF cannot: it builds around your current fitness and available days, it sets the pace for every session, and it adapts when life interferes. My code ANDY2 gives you two weeks free to judge for yourself.
Is Runna good for London Marathon 2027 training?
Yes. Runna builds plans around specific goal races including London, with your target time, current mileage and available training days factored in. The standard trial is seven days and code ANDY2 doubles it to 14. It is what I am using for my own place on Sunday 25 April.
About the Author - Andy Hood
Andy Hood is an ultra and endurance runner based in North Devon. Following a cancer diagnosis and treatment in 2021, he has completed multiple ultra marathons including a 170 mile run to Land's End on the South West Coast Path and two completions of the 160km Tour du Mont Blanc.
He will run the 2027 TCS London Marathon on Sunday 25 April for The Robin Cancer Trust.
He writes about running and endurance at runningwestwardho.co.uk.
Sources
TCS London Marathon will expand into a two-day event in 2027, Abbott World Marathon Majors
How much running is too much? A new take on injury risk for runners, British Journal of Sports Medicine blog, 2025
Carbohydrates for training and competition, Burke, Hawley, Wong and Jeukendrup, Journal of Sports Sciences, 2011
Managing your subscription and how Runna Premium works, Runna support
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