A beginner's guide to interval training

High-intensity interval training can make you fitter and faster... but was it and how do you do it? We bring you up to speed

high intensity interval training
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When you start following a training plan for the first time, you'll likely come across the term 'interval training' fairly quickly. If you've just started out on your running journey, it's a session you may not be all that familiar with. But add it into your weekly training mix and you'll likely feel the benefits pretty fast.

What is interval training?

Interval training (also known as high-intensity interval training) is a form of speedwork that's designed to get you used to running at faster speeds and, used well, it can do wonders for your fitness.

When you first started running, you probably followed a walk/run plan for a while – bursts of running interspersed with short walk breaks to recover. Interval training is based on the same principle. In simple terms, you run faster for a bit, before taking an ‘interval’ of slower running (or even brisk walking) to recover and get your breath back, before doing it again for a number of ‘repeats’.

Benefits of interval training

If you've been running regularly for a while now, but are no longer seeing any noticeable improvements in your fitness, it's likely you've hit a performance plateau. This happens when your body has adapted to the stresses you're placing it under during each training session. So, while those runs probably feel easier now, you're no longer seeing any positive change in terms of fitness, strength and speed. However, incorporating an interval training session into your weekly schedule could change all that. As well as helping you get faster, a regular weekly interval session could:

  • Burn more calories: a slow and steady run is all well and good, but if you push yourself during an interval session, your body has to work harder to recover afterwards, which burns more calories even after you've finished exercising.
  • Boost your heart health: high-intensity interval training (HIIT) seems to be a good way to go if you want to keep your ticker in good working order. A 2022 systematic review, published in Frontiers in Cardiovascular Medicine, found that high-intensity interval training is better than medium-intensity training at improving cardiorespiratory fitness.
  • Leave you with more free time: interval training is a great way of fitting in a quality session in a short amount of time – great if you're squeezing in your running sessions around other commitments
  • Give you a runner's high: pushing yourself to run faster for short bursts can see those endorphins (the feel-good hormone) surge, leaving you feeling happy and energised!

    How does interval training improve your speed?

    OK, so intervals aren't exactly the most comfortable sessions, but if you want to improve your speed, you actually have to run faster and intervals are a great way to start.

    'Interval training is an excellent way to improve speed,' says Omar Mansour, certified running coach and WithU fitness trainer. 'This is because running with a combination of intervals forces your body to take on higher anaerobic capacity, allowing you to go for a longer time at a faster pace as a result. In a nutshell, exposing yourself to harder efforts and faster running will cause speed adaptations to happen.'

    Is interval training good for beginners?

    Definitely! Remember, those early walk/run sessions you did when you first started running were a form of interval training, so you're actually already familiar with the sessions. Now it's simply about pushing yourself to run that bit faster. And remember, those recovery intervals can still be a brisk walk if you need them to be – it's all simply about taking it at your own pace.

    How often should I do interval training?

    Interval sessions will do wonders for your race times, but remember, these are tough sessions, and your bones, tendons and muscles need time to adapt to the stresses of regular training.

    'Interval training takes a high amount of energy and causes a high amount of stress on the body,' says Mansour. 'As intervals are extremely tiring, as opposed to lower-intensity forms of exercise, you need to be careful that you don’t obtain an injury or get to a session without optimal recovery. Start with one interval session a week and then gradually build up from there.'

    Mansour says that, because of the high intensity it involves, you should do no more that three intervals sessions in a week – and then only if you allow for adequate rest and recovery in-between.

    How fast should I run each interval?

    During an interval session, you will run for a set amount of time (or distance) at a high intensity level, before jogging or brisk walking for a set amount of time to recover, repeating until you've finished the session. But how to judge your pacing? After all, there's no one pace that fits all – and it also depends on the type of interval session you're doing, as Mansour explains:

    'The pace all depends on your level of fitness and your session objective, and how long the interval is,' he reveals. 'Typically, shorter intervals mean a higher intensity and earn you more recovery to keep the quality.'

    One of the easiest ways to gauge your pace is by using the perceived rate of exertion (PRE) scale – where 1-2 equals very light intensity and 9-10 equals maximum intensity.

    When you're first starting out, for short intervals of 30 seconds to one minute, aim for a PRE of 8 or 9 (your recovery intervals should be at a light intensity of around 3 to 4). For longer intervals of around two minutes, aim for a PRE of 6 to 7.

    But what does all this feel like? If you're struggling to gauge whether you're pushing hard enough (or too hard), do the talk test: try speaking out loud. If you can only say a word or two, that will be your 8 to 9 intensity pace. If you can say three to four words, that's your 6 to 7 intensity pace.

    In an ideal interval session, you also need to aim to run your final interval at the same pace as the first. It can take practice to get it right, but finishing strong is great for your fitness… and your confidence.

    How to vary your interval sessions

    When it comes to intervals, there are three variables: the length of the intervals, the number of intervals and the duration of the recovery intervals. This means interval sessions are easily tweakable, and the choice of session can depend on your fitness level and/or goal race distance. Take time to learn what works for you – at first, it’s better to build up gradually, with perhaps just four to six shorter intervals, with longer recoveries in-between. As you progress, your pace will improve, your recoveries will be more effective and you’ll be able to run faster for longer.

    Simple interval sessions for beginner runners

    For those new to interval running, the following is a great and simple first session to try:

    • 5-minute gentle jog
    • 1-minute fast interval (at 8-9 PRE)
    • 2-minute recovery interval (jogging or brisk walking, 3-4 PRE)
    • Repeat x 4-6
    • 5-minute gentle cooldown jog

      For a more varied session, Mansour suggests the following:

      • Warm up with a brisk jog for 5 minutes (around 35% intensity)
      • Run at around 65% effort for 1 minute
      • Go back down to a jog for 2 minutes at 50% effort
      • Run at 70% effort for 1 minute
      • Jog again for 2 mins at 40% effort
      • Run for 1 minute at 65% effort
      • Jog for 2 minutes at 50% effort
      • Run for 1 minute at 70% effort
      • Jog for 2 minutes at 40% effort
      • Ensure you cool down at the end for 5 mins at 35% effort

        (The above session is available as a guided interval session for beginners on the WithU audio fitness training app)

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