Everything you need to know about interval training

Getting started with interval training

If you’re following a training plan, you might have seen ‘interval sessions’ mentioned further down the road. For new and experienced runners alike, intervals are a great way to build the speed, endurance, and stamina that’s needed to run strong and race well.

Find out more about getting started, what’s involved, and how to get the most out of your interval sessions, below.

What are intervals?

Interval training describes any run or workout where you alternate short periods of faster or high-intensity work with periods of active recovery.

In practical terms, an interval session will have you running at a fast pace over a short distance with a short break in between where you’re either walking or jogging.

See below for an example session:

• 3 x 2 mins, with 1 min walking recovery
• 3 x 1 minute, with 1 min jog recovery
• 3 x 30 seconds, with 30 sec jog recovery
• 3 x 15 seconds fast, with 30 sec jog recovery

How fast should I run?

The speed you do each run at will vary from plan to plan. Some running plans give a clear number when it comes to pace (“at 5k speed”), with others going more by feeling (“fast” or “all out”).

What’s important is that you’re pushing your body during the running sections of the session.

How long does each session last?

One benefit of intervals and track sessions is that you’re not running for long. The sessions can be gruelling, but unlike your long run, you’re not running for long.

The running portion of an interval session typically lasts anywhere from 15 minutes to around half an hour depending on your speed and the focus of the workout. Add in ten minutes for warming up and cooling down, and you’re looking at around an hour per session.

How often should I do intervals?

This is a difficult question to answer without more information about your goals and ability.

For beginners, we recommend gradually introducing interval sessions over time whilst building up your weekly mileage in line with your training plan and goals.

Start with one interval session per week and gradually increase frequency as your fitness improves. For experienced runners, introducing intervals is a little easier as you likely have better running mechanics and a more solid aerobic base to build on top of. Depending on your plan, you may want to stick with one challenging session per week or introduce a second or third session.

No matter what your experience, it’s important you don’t neglect rest and recovery in favour of adding additional sessions. Always prioritise sleep and don’t overwork your body as this can result in overtraining which will ultimately make you slower over time.

Does my heart rate matter?

As technology continues to advance, there are more and more measurable metrics becoming available to runners.

Being able to monitor your heart rate is a useful indication of how hard you’re working during a session. When viewed next to pace, it can give you a good understanding of how fast you and how hard you need to push yourself during the running portion of an interval session.

If you’re new to running or simply aren’t interested, it’s not a running essential. Whilst you can purchase heart rate monitors and smartwatches at a fairly affordable price nowadays, you can just as easily run a good quality interval session using pace and a rough estimate of intensity as your guide.

Are there performance benefits?

Improve speed over short distances

The more you run, the quicker you become. Intervals are really beneficial for developing speed over a shorter distance because they allow your body to adapt to increased intensity over time.

Shorter, more intense sessions also help maintain and develop fast-twitch muscle fibres that are needed for quick, agile movements. These muscle fibres are responsible for aiding the powerful movements we need to effectively sprint and run quickly.

Improving your speed over shorter distances will also make running slower and longer feel easier. You’ll develop resilience and the ability to adjust your speed and intensity as you run which can help when pushing through the more difficult sections of a race or a longer run.

Build endurance and stamina

Interval training can significantly increase your VO₂ max, which is a measure of the maximum rate at which the body can use the oxygen we breathe in.

By repeatedly pushing your cardiovascular system to its limits during intense interval sessions, your body adapts by improving its ability to deliver oxygen to your muscles to build endurance over time.

Interval training is also a great way to help raise your lactate threshold. This refers to the intensity at which your body starts to produce more lactate than it can clear out.

By regularly putting your body through short bursts of intense effort that are followed by rest or recovery periods, you teach your muscles to better tolerate and clear lactate. This means that over time, your body becomes familiar with what’s required to sustain higher levels of effort for longer periods.

Break up the monotony of training

Running at different speeds is a great way to make training feel varied and interesting. Your brain is far more likely to stay engaged with a workout when you change factors like speed and gradient every so often.

If you find single-speed runs monotonous or your normal route isn’t hitting the spot, an interval session can help break things up and inject some excitement into your running routine.

With interval training, each part of the session serves a specific function, whether it's building speed, endurance, or strength. This sense of purpose and focus can help you stay motivated and engaged throughout the workout.

Another great mental aspect of intervals is how they can help make a workout feel less daunting and more achievable. Adopting a segmented approach where you focus on one interval at a time can make your sessions feel manageable because you’re not asked to face one big chunk of distance that might look daunting on paper.

Are there different types of intervals?

HIIT intervals

HIIT intervals involve alternating between short bursts of maximum effort (high-intensity) exercise and brief periods of rest or low-intensity recovery. These intervals are typically shorter in duration but performed at maximum intensity.

When it comes to running, a HIIT interval session will involve short sprints or fast-paced efforts lasting 20-60 seconds, followed by short rest or recovery periods. For example, a HIIT interval session could consist of 10 sets of 30-second sprints followed by 30 seconds of walking or light jogging.

HIIT intervals are great for improving cardiovascular fitness, metabolism, and overall caloric burn when compared to steady-state cardio.

Pyramid intervals

Pyramid intervals are slightly different as they see you gradually increase and then decrease the duration or intensity of intervals. If you picture a pyramid-like structure with a slope up, a peak, and a slope down, you’ll get the idea.

They typically involve progressively longer intervals followed by a decrease in duration or intensity. For example, a pyramid interval session could include intervals of 200 meters, 400 meters, 800 meters, 1200 meters, and then back down to 800 meters, 400 meters, and 200 meters, with equal recovery periods between each interval.

Pyramid intervals challenge different energy systems and build both speed and endurance. They also add variety to training and can help break through performance plateaus.

Hill repeats

Hill running is a great way to build endurance and stamina. Running uphill at a challenging pace followed by jogging or walking downhill for recovery can help take your training to the next level.

To get started, choose a hill with a moderate to steep incline and perform several repetitions of running up the hill at a hard effort, followed by jogging or walking down to recover.

For example, a hill repeat session might look like 6 to 10 repetitions of running up a hill for 30 to 60 seconds each. If this is too challenging, choose a gentler incline or reduce the duration or intensity of each attempt.

Hill repeats improve leg strength, power, and running form. They also enhance cardiovascular fitness and mental toughness, as runners must push through the discomfort of running uphill.

Fartlek training

Fartlek training roughly translates to "speed play" in Swedish.

During a fartlek session, runners alternate between periods of faster running (such as sprinting or tempo pace) and periods of slower jogging or recovery. The intervals can vary in duration and intensity, and there's no fixed structure or predetermined rest periods.

It’s a playful way of testing the water with intervals, as it gives you complete control of how fast you run and how long you keep going for. Fartlek sessions are flexible and allow runners to spontaneously vary their pace based on terrain, distance, and personal preference.

Fartlek training improves speed, endurance, and mental resilience. It adds variety to training and allows runners to practice pacing and adaptability in different running conditions.

Can I do intervals as a beginner?

Absolutely.

Intervals are often seen as “advanced” sessions that only have benefits for really fit runners who are fast already. This couldn’t be further from the truth.

The reality is that intervals work based on what feels fast to you. Choose a speed that pushes your body, not anyone else’s. Whilst you can attend a track session with a running club, you’ll all run at different speeds once the session gets started.

Are intervals only for running?

If you’re a complete beginner and haven't started running, or perhaps you just don't enjoy it, you can still use this style of training with different exercises.

Take walking for example. Instead of changing speeds, try changing the gradient you’re walking at. If you’re using a treadmill, start with 1 minute on flat alternated with 30 seconds on a 10% gradient.

If you prefer the rowing machine, start rowing 250m at active recovery pace and then 250m at a faster pace. If the Stairmaster is your thing, you could do 1 minute on level 5 followed by 1 minute on level 10.

Can I do intervals on a treadmill?

Treadmills are a great way to do intervals because they allow you to adjust speed and incline. All the information (speed, time, distance) you need is presented to you on a dashboard.

Some treadmills come equipped with a timer that will lower/increase speed after a certain time. This is great for intervals, as you can set the run/rest periods before you start. Other older treadmills won’t have this function, so you’ll have to either manually lower the speed, or step off to the side rails for a complete stop during the rest phase of your session.

Pay attention to your speed while you do this. The belt will continue to spin whether you’re on it or not, so always make sure you’re confident underfoot and aware of your surroundings.

The importance of warming up and cooling down

Warming up and cooling down are a crucial part of every run and intervals are no different. In fact, the slow/fast nature of these sessions makes it even more important.

Warming up

Warming up is all about getting your body moving and increasing your heartrate. This will mean there’s more blood flowing into your muscles and less chance of injury when you start running.

See below for some common interval session warmups:

• Walking to the track
• Dynamic stretches
• Gentle jogging
• Strides
• Skipping

Cooling down

Cooling down does the exact opposite. When you exercise, your heartrate goes up, and your muscles become flooded with blood to accommodate the work you’re putting in. When we stop exercising, we need to bring our heartrate and body back down to a resting level in a controlled manner.

See below for some common interval session cool down exercises:

• Walking home from the track
• Dynamic stretches
• Static stretches
• Foam rolling
• Hydration and nutrition
• Easy jogging after your final interval

Last updated Wednesday 13 November 2024

First published on Thursday 7 January 2016