The Long Run: How Long, What Pace and How to Do It Right
The long run is the most important session of the week for almost any distance runner, and also one of the most often done wrong. Some run it too fast and turn it into a race. Others stretch it out without control and end up injured. Planned well, it is the session that gives you the most endurance. In this guide I explain what the long run is for, how long it should be for your goal, what pace to run it at, which variations exist and what to eat and drink during it.
What the long run is for
It improves almost everything you need for long distances. It increases the number and efficiency of your mitochondria, teaches your body to burn more fat and save glycogen, and gets your tendons, bones and muscles used to handling many impacts in a row. It also prepares your head: knowing you can run for an hour and a half or two hours gives you a lot of confidence.
The strongest adaptations come after the first hour of running, which is why stretching your usual run a little isn’t enough. I explain it in detail in the guide on how to train in zone 2.
How long the long run should be
It depends on your goal and your volume. As a reference, these durations work for most recreational runners:
| Goal | Long run duration |
|---|---|
| 5K | Around 1 h 10 |
| 10K | Around 1 h 20 |
| Half marathon | 1 h 30 to 1 h 40 (16 to 18 km) |
| Marathon | 2 h to 2 h 30, not much beyond 3 h (up to 28-32 km) |
Another useful reference is for it to be about a third of your weekly kilometers, and at most 40% if you run low volume. If you run 30 km a week, 20 km is too much. And build it gradually, 1 to 2 km a week, with an easier week every three or four.
What pace to run the long run at
Easy. Much easier than your body wants, especially in the first hour. As a reference, more than a minute per kilometer slower than your 10K pace, and always at a pace where you can talk. It is what is known as long slow distance.
Hold that pace from start to finish. Once you pass the hour mark, holding an easy pace starts to take effort, and that controlled difficulty is exactly what produces the adaptations. If you want to know your exact paces, get them from the training pace calculator.
Long run variations
Most of these sessions should be easy and steady. But as you get closer to a race, some variations help.
In a long run with a race-pace finish, the last 4 to 10 km are at goal pace. It is very useful for the half marathon and marathon, because you learn to hold the pace on tired legs. A progression long run gradually picks up the pace in the last third, without getting hard. And a session with blocks mixes sections at race pace, for example 3 x 3 km, into a long easy run.
Use them sparingly: one every two or three weeks at most. If every long run has a fast finish, it stops being a long run and becomes another quality session.
Eating and drinking on the long run
If it lasts less than an hour and a quarter, drinking to thirst and having eaten well is usually enough. Beyond that, take some carbs, for example a gel or sports drink every 30 to 45 minutes, and drink regularly, more so in the heat.
It is also the best time to rehearse what you will take on race day: the same gel, the same drink, at the same times. I explain it in the guide on how to train your gut and in the one on hydration and electrolytes. To work out how many carbs you need, use the race carb calculator.
Common long run mistakes
The most common one is running it too fast. If you finish wrecked, you haven’t done a long run, you have done a race, and it will take you several days to recover.
The second is stretching it suddenly: going from 12 to 20 km in two weeks is a recipe for injury. The third is putting it right next to your interval or threshold session; leave at least one easy day in between. And the fourth is forgetting to recover: afterward, eat something with carbs and protein, drink and, if you can, make the next day easy or a rest day. If aches appear that don’t go away, check the guide on runner injury prevention.
Conclusion
The long run is the foundation of any distance plan. Match its length to your goal, from a little over an hour for a 5K to around 2.5 hours for a marathon, keep it to about a third of your weekly volume, run it easy from start to finish, add a race-pace finish now and then and use it to rehearse your fueling. Choose well, run better.
Frequently asked questions
How long should a long run be?
It depends on the goal: around 1 h 10 for a 5K, 1 h 20 for a 10K, 1 h 30 to 1 h 40 for a half marathon and 2 h to 2 h 30 for a marathon.
What pace should the long run be?
An easy pace where you can talk. As a reference, more than a minute per kilometer slower than your 10K pace.
How often should I do a long run?
Once a week if you are training for a half marathon or marathon. For 5K and 10K, every week or every 10 to 14 days is enough.
Do I need to eat during a long run?
If it lasts more than an hour and a quarter, yes: a gel or sports drink every 30 to 45 minutes. It is also the best time to test what you will take in the race.
What percentage of weekly volume should the long run be?
As a reference, about a third of your weekly kilometers, and at most 40% if you run low volume. If you run 40 km a week, that means between 13 and 16 km.
