This section deals with …

  • What is a long run?
  • The purpose of long runs
  • How to progress a long run
  • Progression runs
  • Change-of-pace runs

For the scientifically minded

What is a “long run”?

What constitutes a “long run” is obviously relative to your current level of fitness. A long run to someone just starting out on their fitness programme may be 5 or 6 miles, whilst an experienced club runner will consider this an everyday run-out, and an ultra-marathoner may consider 13-15 miles a weekly event.

The purpose of long runs

At the beginning of your training programme your long run should be at an easy pace in order to build what many call “resistance to fatigue” and a strong aerobic base. In doing so, your body undergoes several adaptations (see “For the scientifically minded” below) to help you run further without tiring quite so much. It is helpful to set a pace or effort limit – for example no higher than 70% of heart rate reserve* – to ensure they remain easy.

*Heart rate reserve (HRR) is (your maximum heart rate) – (your resting heart rate)


… and is arguably a better way of measuring physical exertion than heart rate alone. You should find that your HRR increases as your fitness increases.

How to progress a long run

As with all forms of training for an event, the purpose of the long run is to put sufficient stress on your body so it adapts and you come back stronger/faster/fitter. But if you put too much stress on it, you will breakdown, suffer an injury and feel very fatigued. If, two days after a long run, you are stiff and still feeling the effects, then you have probably overdone it and should take it easy until you have fully recovered.

Therefore, the distance of such runs should build up gradually, always taking into account the mileage of your other workouts and hence your total weekly mileage. The generally accepted advice is to increase your weekly mileage by 10% to avoid possible over-use injury, but, as yet, there is no scientific evidence to back this up. That said, it is worth following and should be used to calculate how long your training programme should last – if you currently run only 10 miles a week, your programme will necessarily be longer than that of someone who is used to running 20 miles or more each week.

Long runs can progress in a number of ways:

  • Efforts will move closer to your intended race pace.
  • Time spent running in a single workout will increase
  • The distance covered in a single workout will increase
  • And if doing intervals and mixing up the pace, then the time of recovery between efforts will decrease.

These four patterns of progression may be used in any order from session to session and you can even put them together, but do not increase the overall training load too quickly from one workout to the next. Just begin with a workout appropriate to your current fitness level and gradually make them more and more race-specific.

Once you can run continuously at a nice easy pace for 13 miles or so, you can begin to increase the training load by running further with pace variations until you can include a large chunk of this mileage at your goal marathon pace. “Maximising time spent running at or very near your goal race pace in the final weeks of training will maximise your efficiency and fatigue resistance at that pace. (Hudson)”. Such endurance training culminates in a single workout that is your most “race-specific”, which is performed 15 to 10 days before your race. There are various ways of building up to this, such as …

Progression runs

These are runs that increase in pace or effort incrementally over the course of the run. Progression runs teach you how to feel your pace and increase it even when you are tired. These workouts increase the oxygen uptake in a higher percentage of muscle fibres, accelerating turnover by engaging first the slow-twitch muscle fibres then the fast-twitch fibres in the later stages of the run. (These runs are typically performed at a slower average pace compared to an equivalent tempo run, due to the demands of acceleration on the muscles and aerobic system).

Change-of pace runs

These involve alternating between slower and faster paces during a continuous run. They can be done over any distance or duration, and the pace variations can be structured or spontaneous. These runs teach the body to run fast without complete recovery. If the fast sections are run faster than lactate threshold, causing lactate to build up, the slow-twitch muscles that are activated on the slower sections clear the lactate accumulation. This improves your muscles’ ability to use lactate as a fuel.

Most marathon training programmes will have you do a long run every week and build up the distance gradually, ending with a single 20-22 mile run within 2 or 3 weeks before your race. Some suggest that once you reach a basic level, it is not necessary to do a long run every week, but propose such a run once a fortnight, maybe even less often, as it is more important to focus on your fitness rather than a high frequency of long runs. But whatever your point of view, it is important to appreciate that too many club runners think they have to pound the roads and rack up the mileage week in, week out (whilst neglecting other workouts that develop strength, speed, lactate threshold, aerobic capacity and running form) and then wonder why they get injured! Indeed, it is a good idea to build in a less onerous week of training now and then to give your body time to adapt and recover. This is perhaps best done the days after a longer run of, say, 16-18 miles, and instead of high-intensity workouts, enjoy a few easy runs.

Of course, it all depends on your race goal – if you are just wanting “to finish” a marathon and are not worried about the time it takes, some, even all, your longer runs can be easy throughout.

For the scientifically minded …

Long runs and endurance training achieve one or more of the following adaptations in your body:

Increase the capacity of the muscles to use fat, as opposed to carbohydrate, which then allows you to run farther before running out of fuel (glycogen) so delaying fatigue;

Increase glycogen storage. By gradually increasing the distance of your long runs, you’ll gradually increase your glycogen storage. The faster you run, the more glycogen you burn, so running your long runs at a relatively brisk pace is a more effective way to deplete your glycogen stores (and thereby provide a stimulus for those stores to increase), than running them slowly;

Increase capillary density. Long runs and other forms of aerobic training increase the number of capillaries in the working muscles by providing a sustained demand for oxygen. This allows your muscles to work at a higher level aerobically;

Increase the number and size of mitochondria. Mitochondria are the aerobic energy-producing factories in your muscle cells. Endurance training also increases aerobic enzyme activity in the mitochondria enabling your muscles to produce more energy more quickly;

Give fast-twitch fibres more of the positive characteristics of slow-twitch fibres. Amounts of the two types of muscle fibres (slow- and fast-twitch) in your muscles are genetically determined. Sprinters use fast-twitch and distance runners use slow-twitch muscle fibres, but whilst you probably cannot change the number of such fibres, it is thought that you can encourage some of your fast-twitch fibres to become more like slow-twitch ones by endurance training;

And finally, your long run gives you the confidence that you can complete the distance of the target event.


Running Science – Owen Anderson

The Science of Running – Steve Magness

Brain Training for Runners – Matt Fitzgerald

Run Faster from the 5k to the Marathon – Brad Hudson