When you first start running it can feel like you’re working at your absolute maximum every step of the way, but it only takes a few outings for your body to adapt and for you to learn that you have several speeds in your locker. Mixing up the types of runs in your training can greatly improve your fitness.
Slow and steady runs are great for building stamina and will feature heavily in any good-quality half marathon training plan or marathon training plan, but if you want to increase your speed across any distance you need to run fast, and the best way to do that is with interval runs.
We spoke to GB Age-Group triathlete Chris Stanton, performance master trainer at Third Space London and a British Triathlon coach, to get more info about the benefits of interval running and some sessions runners can try. You’ll find all of Stanton’s advice below, but first here are a few key takeaways:
- Interval running teaches your body to work at higher intensities, and helps you to get faster.
- Pace yourself in interval sessions—aim to complete all your reps at the same kind of speed, rather than doing the first too fast and slowing down from there.
- The duration of intervals should change in line with your aims. Short, fast intervals improve your sprint speed, while more controlled intervals of 800m-1km are better when training for 5K and 10K events. Your intervals can be longer still when marathon training.
- Fartlek training is a good place to start with intervals, since it doesn’t have to involve prescribed distances.
- It’s a good idea to do intervals alongside other people to increase accountability and make the sessions more fun.
- Don’t do interval sessions too often. As a general rule only 20% of your weekly running should be done at a high intensity.
What is interval running?
The best way to describe it is intermittent training, so periods of work and periods of rest. You run for a time, and you rest for a time, and that rest could be walking, or it could be static, or it could be a little bit active.
What are the benefits of interval runs?
It teaches the runners to run at a higher intensity than they’re used to, and it means they can get more intensity in a session. Novice runners tend to look at volume—how long they run for. At a certain point, that’s going to plateau. When you bring intensity in, then your workload is based on both intensity and volume. You start to increase your ability at certain speeds, and you can run at a faster speed than you could before for a longer period.
Another benefit of doing intervals is you get both anaerobic and aerobic adaptations. It can also be very efficient for a lot of people, especially if they’re focusing more on calorie burn rather than performance.
It’s also a lot of fun, and it’s sometimes more manageable for people because they know they only have to work for a short period of time. People that are a little bit more deconditioned or new to running, it’s mentally very tough to run for long periods.
How often should you do interval runs?
We talk about the 80-20 rule, where 20% of your running in a week is at a higher intensity, though that could change if you’re training for a particular event.
Do intervals of different lengths have different benefits?
Short, sharp intervals focus more on leg speed control and firing up the neuro system, and muscle recruitment and activation. They’re really good for helping you to move quickly.
Then when you come to events like 5Ks and 10Ks, you want to move quickly for a long period of time, so you wouldn’t be running at those higher speeds. For those I’d start to reduce the speed you’re running, but lengthen the intervals, so they’re closer to 800m or 1km, slightly above target pace. That would improve your ability to run at that speed with control.
Why is it important to keep your pace even across intervals in a session?
You’re targeting a specific adaptation, a specific development, so you want the stimulus to be the same. You could be running at the same speed every interval, but you might find that your heart rate increases so by the latter intervals you should be at 80%-plus of your max heart rate, or even up to 95%, depending on the type of interval.
If the first interval is all-out, the last one drops, so that you decrease intensity. The stimulus isn’t the same and you’re getting less work at the stimulus you want.
What kind of interval runs would you recommend for 5K training?
I’d do intervals of anything from 30 seconds up to three minutes. That’s around 150m-800m repeats.
When you’re further away from the event, you do the short, sharper intervals, and then you elongate that and try to maintain that speed. Build what we call speed endurance.
I would do 1:1 recoveries—whatever you work for, you have recovery equal to the work. Start with 30sec/30sec, and then in the next session six times two minutes, with two minutes recovery. Then I’d do four by four minutes.
There’s three quite standard interval sessions based on time, but you can also calculate your distances based on how fast you’re running and your target paces. If you do it on a track a lot of intervals are based around the 400, 600, 800m reps—multiples of 200.
What intervals should you do for marathon training?
Working on your 5K speed is still really beneficial, but marathon intervals will be something like three to six sets of 20-minute work periods, working slightly above your marathon pace. You want to be running just a fraction quicker than that, because that teaches you to run at that speed.
If you’re new to interval running, what kind of sessions should you start with?
With new people I would say, “I want you to run for as long as you can, at around an intensity of eight out of 10. When you feel you want to rest, rest.” Essentially, what you’ll do is build a natural instinct for intensity, and the more they do the more that instinct will increase and they’ll be able to cope with more.
Another option is when they’re out running they could pick a lamppost or a tree in the distance, and go quicker towards that. Then pick something else in the distance and walk to that. It’s what we call Fartlek training. It’s not as structured as regimented time intervals, but you have periods of work and then periods of rest, and it’s always good fun.
Do you have any other tips on how to approach interval running?
I definitely think that people run too quickly. Just be mindful that it’s not always about maximal speeds. And don’t do too much too soon—use small stepping stones.
Have a clear plan and above all, enjoy. If you don’t enjoy interval training it might not be for you, but I haven’t come across many people who don’t enjoy it. There’s definitely an endorphin rush and euphoria around it.
Maybe team up with somebody else and do it together. Having a buddy drives a level of motivation and accountability. You’re in it together—there’s a sense of community and someone else is there suffering with you, which does make it nicer.
Should runners do intervals when cross-training?
Sometimes doing intervals either on a bike so there’s no ground contact or on a rower can be really beneficial, resulting in aerobic enhancement without the same impacts of running.
- Pro Tom Evans on the benefits of cross-training for runners
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Nick Harris-Fry is a journalist who has been covering health and fitness since 2015. Nick is an avid runner, covering 70-110km a week, which gives him ample opportunity to test a wide range of running shoes and running gear. He is also the chief tester for fitness trackers and running watches, treadmills and exercise bikes, and workout headphones.