The science behind running your best marathon

A masterclass in the art and science of marathon training from running coach Sam Murphy.


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There’s no single ‘correct’ way to train for a marathon. Even at elite level, coaches and athletes approach the distance in different ways. This variation reflects attitudes and beliefs, training culture, role models, goals and experiences. But it’s not that the experts disagree about what they’re trying to achieve; they just have different ideas on the best way of doing so.

The fact that a range of different approaches to marathon training can work illustrates another important point: we are all unique. What works best for one runner’s body doesn’t necessarily do the same for another. What brought success for you at one time may not work for you now, or in the future, when your training status and experience level have changed. That’s why it’s important to bring yourself into the equation when considering your approach to training.

While approaches vary, there’s certainly more to running a good marathon than simply logging a lot of kilometres. You need a range of different training intensities to hone different fitness attributes – low-intensity training improves fat utilisation, high-intensity running raises VO2 max and high mileage promotes running economy. All of these ingredients should be part of your marathon training equation. What else can help you to hit a perfect balance?

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Varying the intensity of your training is the key to success

Going long

Long runs are the linchpin of marathon training. They’re the most specific session to prepare for a marathon, and being on your feet for a long time builds cardiovascular endurance and resilience within the musculoskeletal system. There’s also an important psychological element– having to carry on running as fatigue hits builds mental strength, confidence and your capacity for tolerating discomfort.

You’ll also need to get to grips with fuelling and hydrating on long runs – which is great preparation for the race itself. The gastrointestinal system adapts to fuelling through practice, but just as important is getting used to the practicalities of carrying your fuel and drinking on the move.

Traditionally, marathon programmes include a weekly long run (with the odd break) that builds in distance each week, culminating in the longest long run, two to four weeks out from the race. This doesn’t really make sense. Why would you do your longest ever run just a few weeks before your longest ever race? How well are you going to recover between that peak run and the race? It’s far better, I’ve found, to reach (or get close to) maximum long-run distance earlier in the programme (revisiting it occasionally), so you can then switch the training focus to how fast you can run over a long period.

The traditional marathon training approach also assumes that if you don’t do a long run every week, you’ll somehow lose your ability to do it, which simply isn’t true. Actually, it takes 21 to 28 days for your body to absorb the benefits of a long run and instigate the adaptations it triggered. That’s not to say that you need to have a gap of three to four weeks between long runs (running when you’re tired is an important part of training – building ‘fatigue resistance’). But I’ve found most runners thrive better without the relentless grind of weekly, ever-longer long runs.

The practice of including some kilometres at goal marathon pace (or quicker for runners whose marathon pace in itself isn’t challenging) in long runs has become widespread. There are some really good reasons to do this. But remember, the first goal is to build the run’s duration. You want to be able to handle running 25 kilometres before worrying about going faster within the long run.

Once you reach that stage, adding fast finishes (the last few kilometres or minutes at a quicker pace), repeated bouts at marathon pace or runs that gradually progress from easy pace to quicker will improve your marathon-specific endurance and your ability to resist the fatigue that causes so many marathoners to slow down in the latter stages of the race.

On the threshold

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Training at threshold is an effective way of pushing your LT to a higher intensity, enabling you to maintain a higher speed without experiencing the negative effects it causes within the muscles

Lactate threshold (LT) is the intensity at which accumulation of lactate starts to rise sharply. Training close to the pace/intensity associated with your LT has been shown to be an effective way of pushing that point to a higher intensity, enabling you to maintain a higher speed without crossing the threshold and experiencing the negative effects it causes within the muscles.

Training at LT pace can also improve other variables, such as your VO2 max and running economy, which illustrates the point that training at any particular intensity affects the whole body, not just one specific physiological parameter. The idea that you must be training at intensity ‘A’ for one benefit and intensity ‘B’ for another, with anything in between a sort of no man’s land is misleading.

Back to LT training: first you need to know what your LT pace is and how running at it feels. It’s possible to have your LT measured using blood samples in a lab, but unless you’re going to repeat the measurement regularly, this only provides a snapshot of where you are at that particular time. As your training advances, your LT – and the pace it corresponds to – will improve. That’s why going by how you feel is so useful, either on its own or as an adjunct to pace or heart rate.

But there are some other easy ways of figuring out where your LT lies. Sports scientists tell us that LT typically corresponds to the pace a runner can maintain under race conditions for about an hour. For some runners, this will be your 10K race pace, for others it’ll be a little slower (or faster), but it’s not all-out effort. ‘Controlled discomfort’ or ‘comfortably hard’ are common descriptions of how this effort level should feel. It’s likely to elicit a heart rate of 82% to 90% of maximum.

You’ll be relieved to hear that running as fast as you can for an hour isn’t necessary in LT training. Continuous runs of 20 to 40 minutes (tempo runs) at a pace or effort level a tad lower than LT can be alternated with long intervals (such as six-to-10-minute reps) with relatively short recoveries performed at a pace (or effort level) slightly above it. I also like unders and overs – a session in which you alternate short bouts of the two (faster than and slower than lactate threshold pace). This helps to improve your body’s capacity for recycling the lactate that’s been produced to use as an energy source as you run.

The need for speed

Speedwork is sometimes defined as training intended to improve your VO2 max. I’m using the term more broadly, to cover anything from maximal sprinting to intervals performed at kilometre, 5K or 10K pace. This is because improving VO2 max isn’t the sole aim with faster sessions.

Whether it improves your VO2 max or not, speedwork can benefit your running economy, muscle recruitment, neuromuscular efficiency (the line of communication between your brain and muscles) and running form.

At the fastest end of the speed spectrum is maximal-pace running – sprinting. The average distance runner rarely troubles their fast-twitch fibres because the forces of submaximal running aren’t high enough to require them to be activated. But training the fast-twitch fibres means that when a high force is needed quickly – such as to make it up a steep hill – you have a backup team waiting in the wings. There’s an even more compelling reason, though: when the slow-twitch fibres’ capacity has been exhausted through prolonged effort (hello, kilometre 30!), these fibres can step in to share the workload.

My programs use the ‘speed base’ concept, borrowed from US performance coach Steve Magness. Magness proposes that you need to build a foundation of speed through maximal speedwork. As marathon training advances, speedwork shifts, first to traditional intervals (corresponding closely to VO2 max speed, or the maximum pace that can be maintained for around six to nine minutes) and then to slower, longer reps (5K and 10K pace), which challenge your body in a way that more closely approximates the demands of the marathon. So in the first few weeks of training, the speedwork that sits alongside your long runs – while very high in intensity –is very low in volume and doesn’t drain your energy.

Easy runs

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Even at elite level, the lion’s share of training kilometres are at low intensity.

Easy runs are a distance runner’s bread and butter. Even at elite level, the lion’s share of training kilometres are at low intensity. This enables runners to maintain a high training volume. And studies show that upping mileage can improve performance even when VO2 max doesn’t change.

There’s a continuum, from very easy pace to a slightly more breathless, but still conversational, pace. In the early stages of building mileage, focus on the easier end of
the range. This enables you to increase volume without fatigue or injury risk. Easy-paced running also increases capillarisation and improves running economy.

The most important determinant of an easy run is that it feels easy to you. Often, plans suggest target paces for easy runs that relate to your goal marathon pace. This can work for quicker marathoners (sub-3:30) because their marathon pace is likely to be at a higher percentage of their maximum capacity than a slower runner’s marathon pace. Their easy runs need to be slower than marathon pace, because marathon pace won’t feel easy. But less swift runners often find goal marathon pace does feel easy, and that a suggested easy run pace of 25% slower may feel like a trudge and result in poor technique.

That’s why I recommend going by feel or heart rate, as well as checking that your pace remains consistent on the run. If you start easy runs at a faster pace than you end up finishing them, it’s a hint that you’re going too quick.

The most important determinant of an easy run is that it feels easy to you

Going steady

When you’re into the swing of marathon training, your easy runs can get a little quicker – described as ‘steady’ runs. Many runners mistakenly perform their easy runs at this slightly quicker pace, which can make building your endurance base unnecessarily hard.

Steady runs are often defined in relation to goal marathon pace (eg, 5% to 10% slower than goal marathon pace). But again, this won’t necessarily hold true for less speedy runners whose steady run pace may be perfectly aligned with their marathon pace, or even a little quicker.

Putting a plan together

How do you fit all these session types into a plan without overwhelming your body? Let’s talk about ‘periodisation’.

This is the concept of breaking down training into distinct phases, each with a specific focus. The important thing is that the focus of training shifts as you go along.

Originally, periodisation was seen as a set of discrete stages. For example, a base endurance phase, followed by a strength phase, then a speed endurance phase. But some coaches began to wonder, if all of these aspects of fitness are important for the marathon, won’t laying one aside while you focus on another sacrifice the gains achieved? This led to a different approach: ‘non-linear’ periodisation, where you don’t disregard any aspect of fitness that you’ve already developed.

I’ve found this to be an effective way of addressing all the necessary fitness requisites of marathon training without overloading a runner. It also makes a plan less monotonous. The phases of training I use in my plans are: ‘Training Phases: As Easy As 1, 2, 3’.

Foundation phase: Building a base

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The endurance base prepares you to handle a high volume of running

The first priority for a marathon is to build a good aerobic or endurance base – it’s the foundation on which we’ll later lay the stones of more specific training. Building an endurance base is about volume (that’s the amount rather than intensity). Runs are performed at a comfortable pace, so you can continue for long enough and repeat often enough.

The endurance base prepares you to handle a high volume of running. ‘High’ is relative – for an elite athlete it could mean 200 kilometres in a week, which I don’t recommend! I don’t concur with coaches who state that to run a good marathon you must be running 80 kilometres a week. In fact, I’ve often found that runners attempting this (alongside busy family lives) actually do better when they reduce their mileage. But be realistic and acknowledge that you need to include sufficient mileage on a consistent basis– racing 42.2 kilometres is a big ask if you’ve never exceeded 30 kilometres a week.

So what else goes into the foundation phase? With our focus on building volume, it’d be foolish to throw in lots of demanding interval work and LT training. But including small amounts of high-intensity work serves as a foundation for subsequent speedwork and gives your body a novel training stimulus without adding too much load. Your sprint training will contribute to the activation of a greater percentage of muscle fibres, and also increase the speed at which your brain sends signals to your muscles, making you run more efficiently and economically over time.

The foundation phase is also a good time to introduce some strength and conditioning work, which will improve your resistance to injury and fatigue as the marathon training progresses.

Development phase: Building endurance and speed

By the time you transition into the development phase, your running volume will be close to its peak, as will your long run distance. The aim now is to maintain it, which doesn’t require as much input as building it. This means you won’t be doing increasingly longer long runs, freeing up capacity to raise the intensity of some of your other runs with the goal of improving your ability to sustain pace over distance.

You should be doing more of those slightly-harder-than-easy steady runs and LT training in the development phase. By nudging your lactate threshold upwards, remember, you’ll be able to maintain a higher proportion of your maximal capacity during prolonged periods of running.

The focus of your speedwork also shifts in this phase, moving away from maximal-intensity sprints and towards interval training at intensities ranging from VO2 max (which typically equates to the best pace you could run two to three kilometres at) to 5K or 10K pace. There’ll also be some hill training to develop your strength and speed endurance, and to vary the biomechanical effort from flat terrain. Not wanting to let go of what you’ve achieved through your training so far, you should still be checking in with base speed now and again through sessions that include hill or flat sprints as well as strides.

Specific phase: Honing in on marathon pace

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The final phase of marathon training is the perfect time to practise your fuelling and hydration strategy

This phase is all about specificity. The aim is to improve your capacity to resist fatigue at marathon pace. Physiologically, it’s about how well you can resist the declines in lactate threshold, oxygen uptake and running economy that accompany fatigue. Some long runs now become more focused – not just easy kilometres, but bouts of running at race pace, or long runs that start easy but finish hard. Shorter runs close to goal pace are also valuable – helping you maximise efficiency at that particular pace and strengthening your feel for the right pace so you’re less likely to make costly pacing errors on race day.

A ‘dress rehearsal’ (not of the full 42.2 kilometres) is a really important run to include a few weeks out from race day. Run it on the same sort of terrain you’ll be racing on, ideally at the same time of day, and include some marathon-pace mileage. Perhaps the most valuable benefit of this run is building confidence, but it also serves as an advance warning system about anything that isn’t going right. Perhaps your fuelling strategy isn’t delivering or your socks give you blisters. Of course, the specific phase isn’t exclusively about marathon pace. You still want to maintain the speed and strength endurance built earlier in the plan, and you can do this with lower-volume workouts that won’t cause excessive fatigue.

Taper phase: Winding down

The final training phase is the taper or ‘winding down’ period. Here, focus switches from training to recovery, from gaining fitness to consolidating those gains before race day.

The role of cross-training

It might sound odd to hear that cross-training can play a valuable role in your marathon program, but alternatives to running, such as cycling, elliptical training or rowing, can add to (or help you maintain) your training load, while non-cardio activities including yoga and Pilates can bring balance, supporting and complementing your running.

Why not just run more? Maybe you’ve learned from past experience that high mileage raises your own personal injury risk. A weekly bike ride or swim could provide an additional cardiovascular workout without increasing the load on your joints. Perhaps you just want more variety – you could swap an easy run for an exercise class, or a long run with a mid-length run followed by a bike ride, which would reduce the volume of running while still maintaining the workout duration.

Don’t see cross-training as a way of upping your training just because you think more is better, though. It still forms part of your overall training volume and can deplete glycogen, create muscle damage and fatigue, and require recovery. During marathon training, you’re almost certainly going to be running more than usual already, so trying to swim, hit the gym and cycle on other days may tip the balance too far. This is particularly true if the cross-training activity is one your body is not accustomed to. Swimming might sound less stressful on your body than running, but if you haven’t been in a decade, then completing 50 lengths of the pool might feel pretty exhausting.

And as useful as cross-training can be, it’s not a like-for-like substitute. Your heart and lungs may not have a clue what type of activity you’re doing, but your nervous system – which governs muscle fibre recruitment and hones your movement efficiency – certainly does. That’s why specificity is one of the principles of training – and why running is the best training for runners.

Cross-training through injury

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If you can’t run at all, cardiovascular cross-training can help minimise fitness losses.

Judicious use of cross-training can enable you to maintain, or even gain, fitness when you’re managing a niggle or coming back from injury. You may be able to run a little but not enough for marathon training, so you can supplement this with cross-training to help you build volume without overdoing things.

If you can’t run at all, cardiovascular cross-training can help minimise fitness losses. The best activity is the one that causes no pain to your injured area, so you will need to test different options to see what feels right. One of the most effective, and least impactful, options is aqua running. Cycling, walking, swimming and cardio machines, such as the rower or elliptical trainer, are also good options to try out. I once coached someone who developed shin splints midway through marathon training. We moved all his training to the stationary bike and pool, simulating the planned running workout in the cross-training activity. If a session was geared towards improving LT, he did long intervals at a comfortably hard effort with short recoveries in between. If it was speedwork, he completed intervals of hard aqua jogging, interspersed with gentle treading water. Hills were replicated by pushing a heavy gear on the bike. On race day, he still managed to achieve his sub-3:30 marathon goal.

Complementing your running

Cross-training can play a supportive or complementary role to your running. Activities such as yoga and Pilates – as well as strength training – fit in here. They provide balance to your programme and address some of the physical qualities that running doesn’t develop, including good posture, balance, core strength and mobility.

People often ask when to do these activities. On rest days? After running? The answer depends on how challenging and intense the activity is. With the exception of strength training, I would generally expect this type of cross-training to be low intensity and therefore it doesn’t matter much when you do it.

Ultimately, the best way to determine whether to include cross-training in your marathon-training plan is to ask yourself what purpose it will serve. It needs to be there for a reason (even if that reason is simply because you enjoy it), or you risk adding to the stress that running is already placing on your body.

How to progress your long run

‘Long’ is relative. If you haven’t run for longer than an hour in the past three months, 75 minutes is long for you. If you run long distances most weekends, you might consider anything less than 24 kilometres a breeze.

The long runs in my training programs begin at 20 kilometres. I believe you should already be comfortable running close to half marathon distance from day one of your marathon-training program, so distance or duration can build at a manageable rate while giving you sufficient recovery. If you’re not there yet, make building weekly mileage and long-run distance your focus before embarking on a marathon plan.

To lengthen your long run, take the duration or distance of the longest run you’ve done in the previous four weeks as your starting point and add no more than 10 minutes or one kilometre to that. Build by 10 minutes or one to three kilometres each time you’re ready to increase it. Don’t add distance every week. It’s fine to stick to the same distance for a couple of weeks sometimes, drop to a shorter run or take a break from the long run altogether.

A word about hills

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The focus of hill training changes throughout the marathon training cycle to meet the demands of training at that particular time

You’ll often see the terms ‘hill training’ or ‘hill reps’. Without context, these are rather vague – 10-second hill sprints have a very different training effect to 60-second repetitions or a continuous tempo run on a hilly route.

Hills subtly change the demand of a run because you have to overcome gravity, increasing the load on your cardiovascular system and engaging more muscle fibres, building leg strength. A gentler hill puts the emphasis more on speed, while a steeper hill focuses more on strength development. Like speedwork, the focus of hill training changes throughout the marathon training cycle to meet the demands of training at that particular time.

Doubling up

‘Double days’ are days on which you run twice. Elite runners use them to increase their overall training volume. Should you? It depends. If you have two or more non-running days, you might be better adding a run rather than doubling on an existing training day. Unless it’s easier for you to double up on a practical level – for example, if you run commute.

There’s some evidence that double days offer ‘two bites of the cherry’ in terms of physiological response to training. One study found that training twice a day every other day improved endurance capacity more than daily training; however, other research found that although many training parameters improved, this didn’t translate to enhanced performance.

You can use double days as an alternative to lengthening a single run (except your long run) to the point that it becomes too long in terms of your time or energy availability. Two six kilometre runs are less depleting than one twelve kilometre run, even though both add the same amount to your weekly mileage. That said, part of the purpose of training is to create a certain amount of fatigue, which then leads to adaptation, so splitting runs into two to escape fatigue isn’t necessarily the right option, especially when it comes to your long runs.

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