The Marathon Long Run: Training Guide

The Marathon Long Run is a core part of any marathon training plan.

Just as the name suggests, Long Runs are training runs that are longer than regular runs.   

They are your opportunity to increase your maximum mileage as the marathon draws near, and are usually done at a slow, comfortable pace.

Long runs are the most important part of your marathon training schedule – there’s no doubt about it. Your other training runs help build a mileage base and can improve your speed, but the key to getting around those 26.2 miles is all in the long runs.

Why Do Long Runs?

Simply put, long runs increase your mileage capabilities.   They train your body to be able to run for longer distances.

More specifically, these longer runs  . . .

  • aid in capillary development, which is the blood vessels which deliver nutrients and oxygen to muscles – essentially fuelling your run.
  • improve your cardiovascular fitness, training your heart to power your body for longer.
  • boost mitochondria – these tiny cells convert fat and carbs into fuel; they are essential for distance running, and longer runs help develop them.   The research shows that mitochondria development is at it’s peak after 2 hours of training at 50 – 75% of VO2 Max (essentially the conditions you’ll create during your longer runs).
  • Are great mental preparation for your marathon.   Running continuously for hours on end does different things to different people’s heads; some people love it, some hate it.   Some tune out, some tune in.   Regardless, it’s been proven that your brain adapts your body’s performance based on past experiences; so having longer run experience helps your brain know what’s going on come race day.
  • Strengthen bone muscles – while more intense run training can put unwanted pressure on bones, longer runs are more gentle, and actually encourage bone development.

So let’s take a look at some of the finer points of managing longer distance runs with regarding to marathon training . . . 

How Long Should My Long Runs Be?

You long runs should consist of around 30% of your total weekly mileage, per most experts and running coach (ref).

Most novice marathon runners start introducing long-distance runs 16+ weeks before their event – in which case they start out at around the 5 – 8 mile mark, depending on your existing running fitness level.

The length of your longer runs will depend on where you are in your training regime; starting of relatively light, then gradually increasing until you peak 3 or 4 weeks prior to your marathon.   

Your long runs should increase incrementally each week, then taking a step-back week every few weeks to consolidate your mileage gains – as I’ll outline below.

Related: What To Eat The Night Before A Long Run For Maximum Results

Longest Run Distance

For novice and intermediate marathon runners, the optimal longest run distance is around the 20 – 21 mile mark. 

All of our marathon training plans max out around this point, depending on the plan.

It might seem counter-intuitive to train for an event by doing at most 80% of the event distance – and at a reduced pace – but your longest long run distance is a trade-off between being under-prepared, and being over-prepared.

Let’s explore the benefits and drawbacks of long runs to explain why this truncated length is actually optimal:

Doing very long runs – let’s say 23 miles and over – has the advantage of getting your body better adapted to longer distances – your muscular endurance, your VO2 Max, and your mitochondria will all improve.

The drawbacks, however, are more pertinent. For starters, you won’t be doing a 23 mile run in a vacuum, as it were. This very long run is gong to be in the middle of an already-busy marathon training plan, when your body is already being tested and stressed.

Pushing your body to unnecessary lengths means:

  • You’ll take longer to recover from your long run, which may impact the rest of your training
  • You increase the risk of overtraining injuries
  • You increase the risk of burnout, exhaustion, and illness.

So while it might seem like a good idea initially to go for a 25 mile run during marathon training, once in the context of a regular marathon training plan you can see why it might not be so smart.

That’s where the 20-22 mile range comes from.

The general consensus is that this is enough in training to get your body prepared, without overcooking it. And you’re leaving those 4-6 miles on the table for marathon day – when the adreneline of the day will pull you through!

Likewise, there’s little to be gained in a longer run that takes more than 3hrs – 3 hrs 15 mins.   After this point, your body is simply being run down – and your recovery will take exponentially longer.  When planning longer runs, consider not just the mileage but the time on your feet.

Your longest run should take place 3-4 weeks prior to your marathon, after which you should begin to taper.

Related: How Long Should Your Longest Long Run Be?

  • Related: 8 Long Run Variations To Build Endurance
  • Step-back Weeks

    Every 3 or 4 weeks, look to cut back your longer run mileage to around 75% of the prior week.  These ‘step-back’ weeks may seem counterintuitive, but give your body pause for rest.   

    This lets your body consolidate the running gains you’ve made in the prior weeks and recuperate; think of step-back weeks as ‘resetting’ your base running fitness, so you’re ready to push forward and grow during the forthcoming weeks.

    You’ll see step back weeks incorporated into all of our free marathon training plans.

    marathon long run

    What Speed Should I Run During Long Runs?

    The goal of these runs is to increase your endurance – this means time on your feet and mileage, not pace.

    One of the greatest mistakes beginner marathon runners make is to assume they should do all their longer runs at their target marathon pace. 

    The problem with this is that you’re overloading your body – you’re pushing it to run at your target pace for too long.   Instead, your other training runs are about building pace.   Focus on building distance and time on your feet.   That’s it.

    The key is to aim for a conversational pace – that’s a pace at which you could comfortably hold a continuous conversation.   

    This pace gets your body used to burning stored fats for energy and means you’re not over-cooking your muscles (so you can continue to train throughout the week).

    If you have a target marathon pace in mind, then consider running 30 – 90 seconds per mile slower during longer runs. 

     That’s a big variance, right? 

    That’s because pace isn’t important – just keep moving and get the prescribed miles in.

    The Alternative To Slow Long Runs: The Fast Finish

    If you’re an experienced marathon runner, or you simply feed the long slow runs are a little easy for you, you might want to consider mixing things up with a Fast Finish.

    A Fast Finish Long Run is one in which you increase your speed for the final +-30% of the run.

    So you want to perform the majority of your long run as normal – slow and easy, at a sustainable, conversational pace.

    When you’re approximately 70% of the way through your miles, you want to gradually start to increase your pace.

    It can be tough to break your body out of the ‘trudge’ routine it’s been in, which is why you want to increase the pace gradually.

    How fast should you run by the end of a fast finish?

    It is up to you – for intermediate marathon runners, you may want to aim to get close to your target race pace.

    For veterans, feel free to open it up and push harder – go as fast as you are comfortable pushing yourself.

    Most important is to always listen to your body.

    When Should I Do My Long Runs?

    Most runners prefer to do these on weekend mornings.   

    For people working the typical 9-to-5 job, this is simply the most practical time to do it.  You need a window of 2 – 4 hours to complete your longer runs, and afterwards you’re going to be tired.   Therefore most people find Saturday or Sunday mornings to simply be the most feasible time to do them.

    You also want to do them when your body is sufficiently-rested.   It’s fine to do a long distance run the day after a regular training run, but if you’ve been pushing yourself and are feeling burn-out, then that’s a sign that you shouldn’t be going for epic runs. 

    I try and schedule my longer runs for the day after a typical training run, or a cross-training day. I find that doing longer runs as a back-to-back with a moderate workout works well in building my endurance, and allows me to pack a few things into a tight training schedule.

    You should take a rest day the day afterwards – or at least roll back to just some light cross-training.   Depending on my training regime, I therefore do my longer runs on Saturday or Sunday mornings. 

    Our marathon training plans assume a long run on either Saturday or Sunday, but are customisable so you can move things around to suit your schedule.

    Side note: as you get into longer long runs, you should be mindful of runner’s nipple – chafing that begins to irritate after hours of running!

    Fuelling For Long Runs

    As your long-run mileage increases, you should start to fuel yourself during your longer runs as well as before.

    A good rule is that you should be fuelling while running for any run longer than 75 – 90 minutes.   However, you should start fuelling after only 30 minutes of running – if you leave it to the 75-minute mark, you’ll find yourself drained of energy.

    Look to take endurance-specific fuel – this means energy gels and the other piece of high-calorie sports nutrition that sits next to the gels.   Depending on the product, I’ll typically take one gel every 45 minutes, starting from the 30 minute mark.

    Remember to hydrate too. You can get off with not hydrating during a run of under 60 minutes, but once you cross that hour mark you should look to sip water to avoid the sensation of thirst.

    The Marathon Long Run: Training Guide 1

    Practical Tips for Long Runs

    Longer distance runs can be a psychological game as much as a physical one.

    Here’s some tips and things I’ve found have helped me get motivated and power through a longer run:

    1. Find a Buddy.   Longer runs are much easier if done with another person.   Having some company can banish the interminable-plodding sensation that you might feel after dragging yourself out of bed at 6am on a weekend.

    2. Listen to something good.  If you can’t find a running buddy, download a couple of podcasts or a great audiobook to listen to and disconnect as you pack in the miles.

    3. Find a new route.  You can use your longer runs as an excuse to find new running routes and trails – now you need to get more miles in, go and explore further afield and map out an exciting new trail to somewhere you’ve never been before.   Running the longer distances means new routes might be open to you which aren’t feasible for your shorter, mid-week runs.

    4. Long Runs = Dress Rehearsals.   Your longer runs can act as dress rehearsals for your marathon.   As well as trying out all the gear you’re going to bring with you, it’s an opportunity to test out your fuelling and nutrition strategy on the move.   Find out which gels work for you, how frequently you should be taking them, etc.

    5. Enter a Race.   Make things interesting.   If you’ve got a 12 mile long-run scheduled for the weekend, and there’s a local half marathon taking place, go for it!  It’s a great way to prepare for your actual marathon.

    6. Stick to a Plan.   Follow a goal-specific marathon training schedule and simply run to the mileage in the plan.   This takes a lot of guess-work and planning out of your hands – stick to the plan, you’ll do fine.

    How do you tackle long runs?

    Let me know below!

    Photo of author
    Thomas Watson is an ultra-runner, UESCA-certified running coach, and the founder of His work has been featured in Runner's World,, MapMyRun, and many other running publications. He likes running interesting races and playing with his two tiny kids. More at his bio.

    9 thoughts on “The Marathon Long Run: Training Guide”

    1. I am going to start you sub 4 marathon training plan the end of June for my first marathon in November I’m excited but nervous Lol. I have always done a recovery run the day after a long run while training for a half which is typically half the distance of my long run What are your thoughts on this? I know you mentioned to rest or do a cross train day the day after a long run in the article

    2. Hi, On Monday the 11th Oct I signed up to do the Manchester Marathon in April 2022.
      I found you on a web search, read though all of what was there & printed of the couch to marathon in 20 weeks and started yesterday on the training. Today I received an email from you, upon reading this I am now more confused about which training plan I need and what I should buy from the sites to help me achieve the best time I could.

        • Hi Thomas,
          My fitness levels could be better. I use to run but stopped 20 years ago. I have just started one of your training courses couch to marathon in 20 weeks ( walk 2, run 1)
          I am running the Manchester marathon next April who as a PB of 3.33 ( he’s 21) but I know I cant run at that pace. But would like to get between 4.30 to 5 hours

      • Hi Alan I done Manchester few years ago. Signed up again for next year. This will be my 4th marathon. I have tried a few different plans but now realise that the problem was just plodding miles. I am going to follow the sub 4. Starting 15th Nov. This looks a very balanced plan, last one I done had 50 plus weeks. Joining the gym this time, sister has been going last few months and pb at Belfast. Good luck.


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