Need for Speed: Sharpen up your Pace with Interval Training

Ever feel like your running is stagnating? In the past, as long as you put in the training miles, your personal bests used to tumble regularly. Now, despite your best efforts, your times have levelled-off and you’re simply not seeing the steady improvements you used to. You’re training just as hard as before, sticking to your tried and tested formula, but somehow you’re just not getting any better.

What’s going on? The most likely answer is best summed up in the words of Peter Coe, father and coach of former 800m, 1500m and 1 mile world record holder Sebastian Coe, who said:

Runners who train the same, stay the same.”

– Peter Coe

In training for distance running, no truer words have been uttered. Chances are, by sticking to your same old training regimen, you’ve reached what is known as a training plateau. When you first take up running, your body can experience some pretty profound physiological changes as it struggles to deal with the extra load that your new hobby is putting on it. In a relatively short time, you notice that your times improve dramatically, your endurance increases, those extra pounds you’ve been carrying for a while disappear, helping you to fly along even faster. Your legs tone up and get stronger too. All great news!

But soon that steep improvement starts to flatten out. This is your body getting used to the increased demands being placed upon it. It’s your body’s way of saying ‘no problem, we got this’. A key concept of running training, however, is that of progressive overload. In order to avoid a plateau, you need to keeping piling extra pressure on your body (albeit incrementally) so it can never say ‘no problem, I’m used to this’. If you don’t keep adding pressure – in a controlled way – you’ll plateau. Simple.

So what should you do? Well, plateauing is a sure sign that you should change up your training programme and give your body a bit more to chew on. Now, every training plan, when stripped to basics, will incorporate three elements: frequency (how often you run), intensity (how hard you run), and duration (how long you run for). You can change your training plan by upping the ante in any one of these areas.

Increasing the intensity of your workouts by incorporating interval training

This article in particular focuses on increasing intensity (the others are pretty much self-explanatory – either run more often or run further!). One great way of adding intensity to a training programme is through including one day of interval training per week into your training instead of one of your ‘regular’ runs.

The premise is simple: split up your runs into periods where you are running at a hard pace followed by a period of recovery during which you jog slowly or even walk. Other than that, there are no single hard and fast rules – but we’ll walk you through three suggested basic interval sessions.

Benefits of Interval Training

First, though, why should you do intervals? Well, here are just a few of the benefits:

Increased Pace – The most obvious benefit is that they make you run faster. It’s a bit of a truism but if you want to run faster, you have to run faster. The faster-than-normal bursts of speed integral to interval training get your legs used to turning over faster, your heart pumping at a higher rate, and overall they acclimatise your body to running at a higher pace. By putting in sets of faster than race pace repeats, come race day your body will be equipped to handle your target pace because it has been used to running at a higher pace.

Improved Running Form and Economy – Studies show that the most efficient runners run with a higher than average cadence (i.e. the number of steps taken per minute) and an often-cited target cadence is 180 steps per minute or more. Running at a faster than usual pace will naturally increase your cadence – although it will also increase your stride length, which can cause problems if you tend towards over-striding and heel-striking. But making a conscious effort to focus on stride frequency rather than stride length as you run faster can help you become a more efficient runner.

Increased fat-burning – Working out for 30 minutes of high intensity activity interspersed with periods of rest or low intensity exercise have been shown to burn more calories than 30 minutes of moderate exercise. Not only do intense intervals with a high training stimulus beat running at a slower, more comfortable pace when it comes to fat burning, but the extra effort you put in during the harder-paced intervals mean that your muscles require a lot more energy post-workout in order to recover. This is known as the ‘after-burn effect’ in which your body continues burning calories after you have finished running.

Build interval training into your routine to sharpen up and stay ahead of the pack
Three Interval Workouts to Try

Here we suggest three broad interval workouts to try and build into your routine. As a general rule, if you’re training for / trying to improve your 5k time, you will be looking at running shorter, quicker intervals. Conversely, if you’re in marathon or half marathon training mode, then the longer but slower type interval sessions are for you. If you’re trying to beat your 10k personal best, then try the one in the middle.

Back in the day before GPS watches, the ideal place to run intervals was on a 400m track because of the ease of measuring and timing your intervals. In the age of Garmin and Strava, however, finding a local running track is no longer necessary. Try to pick somewhere relatively flat where you can run uninterrupted by traffic and other inconveniences (in Barcelona, the beachfront is probably your best bet).

Short and quick 400m repeats 

Try building one interval session into your training per week over a period of 4 weeks where, after a gentle warm up, you run quarter miles (400m or a single lap of a standard track) repeats at your 5k pace or slightly quicker. In between your fast quarter miles, run the same distance at a gentle jog as recovery. If you are new to intervals, start off with between 4 and 6 sets in the first week, adding two additional sets per week until by the end of 4 weeks you’re running 10 to 12 sets.

With interval training, the goal is to aim for consistency. Try to hit your target pace on each interval. If you find yourself slowing towards the end of your sets, this is probably a sign that you were pushing too hard in the early stages, causing you to run out of puff later on. Ideally, you should be hitting more or less the same splits with each interval (aim for all your splits to be within, say, 5 seconds of each other). If not, adjust for your next session.

Half Mile Tempo Intervals

A great option if you’re training for a 10k. After your warm up, try running 6 to 10 intervals of a half mile (800m approx. or two laps of the track) at your 10k pace or quicker. For a recovery period, try a half mile light jog in between but if you feel fit and strong, you could taper this back to a quarter mile or less.

Again, because you are aiming for consistent splits, it is better to err on the side of caution when it comes to the recovery period – especially when first picking up interval training – because you really don’t want to blow out two sets before you reach your target number of sets.

One Mile Repeats

As the name suggests, you’ll be running whole mile (1600m or 4 laps of the track) intervals here. For your interval pacing, you can either try using your 10K pace or, alternatively, knock around 30 seconds off your half marathon race pace. Aim to do 4 to 6 mile repeats. As with all interval training, the goal is to keep your times consistent so aim to keep each hard-paced mile within no more than five seconds of the others.

For recovery time, start off by halving your goal time for the mile intervals (so, for example, if you’re running 7 minute miles, this would be 3 minutes 30 seconds of recovery). As you get used to running intervals and you find you can hit your mile target splits evenly and consistently, you could taper back the recovery time to 2 minutes. Alternatively (or additionally), you could try dropping your mile target pace by 15 seconds.

Interval training in pictures

We’d emphasise that the above suggested workouts are just that – suggestions – and that interval training comes in all shapes and sizes and can be adapted to suit the individual runner’s needs, fitness or training goal. However you formulate your workout, though, the golden rule is to achieve consistency in your splits. Take a look at this example of what a good, even sets of splits looks like (this is a 15 x 200m interval workout with warm down).

Interval pacing
Solid, even 200m splits at 5 min mile pace with 10 min mile pace recovery

Notice, too, the effect on heart-rate and how it tracks the intervals almost exactly:

Interval heartrate
Heart-rate during 200m interval training

Compare a similar length workout run by the same runner at an even pace:

Steady pace heartrate
Heart-rate during even-paced workout

So give intervals a go. And remember, don’t rest on your laurels – once you find you can handle a training regime with ease, that’s a sign that you are going to need to change it up or you’ll be back on the plateau…

Tell us what you think in the comments below!

Need help with your training? Book a training session with Run Barca.

Powering your run: some science to chew on


Training for distance running. It’s all about long, slow runs and clocking up the weekly mileage – the more the better, right?

Well, not quite. True, while a healthy weekly mileage tally may form the base of your training regime when preparing for a marathon or half marathon, it’s important to build upon the solid foundations of those long miles with some more intensive sessions – strides, intervals, fartleks, set repeats or other exercises that broadly fall under the banner of ‘speed work’. This is particularly so if you are preparing for a 5k or 10k.

But if even if you are training for a half marathon, marathon or beyond, there are good reasons why you will want to build speed work into your weekly training – and these reasons are grounded in physiology and the way your body is powered.

Energy systems used in running: Aerobic, Lactate and ATP-CP systems

Energy is stored in the body in various forms of carbohydrates, fats, proteins and creatine phosphate. Meanwhile, adenosine triphospate – or ATP – is the body’s usable form of energy. The body utilises three different energy systems to turn that stored energy into usable ATP to power our muscles whilst running.

Understanding which of these three energy systems the body is primarily using during your runs will help you to train in a way that targets and improves those specific systems.

So what are the three energy systems?


The first and most important for distance running is the aerobic system. This system uses carbohydrates, fats, or proteins to produce energy and requires there to be enough oxygen available for the working muscles (hence the name). Energy production is slower but more efficient than the other two systems and is utilised in longer term, lower intensity activity. So that long, slow Sunday morning run you do every week? That’s being powered primarily by your aerobic system.

Lactate/anaerobic system

Next there is the lactate or anaerobic system. Unlike the aerobic system, the lactate/anaerobic system doesn’t require oxygen to produce energy. Instead, the body uses stored glucose to produce ATP to power your muscles in conditions when adequate oxygen isn’t available for aerobic metabolism. The anaerobic system is used during short-term periods of intense exercise and can power you for 1 to 3 minutes max. Your kick at the end of a 5k when you’re sprinting for the line? You’re primarily using your anaerobic system right there.

ATP-CP system

Finally, there is the ATP-CP system. This is the quickest form of energy production but can only supply enough energy for a short burst of intense activity like a 5 second sprint.  It’s used when the body experiences a sudden increase in energy demand – for example, when you’re starting up your run or when you’re training explosive hill repeats. This system relies on the availability of creatine phosphate which depletes quickly. Once the body’s limited stores of creatine phosphate are used up, the body must call on either the aerobic or anaerobic/lactate energy systems to sustain continued activity.

Take a look at the diagram below and you’ll see that the three energy systems are not mutually exclusive, but are inter-dependent. As a rule, however, your longer low-intensity runs will be relying more heavily on the aerobic systems whilst your more intense sessions like sprints, intervals and set repeats are going to be predominantly working the lactate/anaerobic or ATP-CP systems.


Energy systems

Smarter training – the fartlek

So, having had a quick crash course in energy systems and metabolism, what does this mean for how we should train? Should we just keep aiming for a high weekly mileage or can we cut some of those long miles and train smarter?

There is probably no wrong or right answer but an interesting case study in training habits can be found by looking at Seb Coe and Steve Ovett’s respective training regimes. Both were elite middle distance runners – and fierce rivals – but they trained in very different ways. At his peak, Ovett was reportedly running an incredible 140 miles per week. Coe, meanwhile, was barely clocking 40, preferring to focus on intense speed work. While it is impossible to say which approach produces the best results, one thing is clear: if you don’t have the time to put in the high mileage weeks, you can get more bang for your buck by running fewer but more intense miles. And if you want to train in a way that hits all three of your body’s energy systems, then look no further than the fartlek.

Fartlek is a Swedish term that literally means “speed play”. It was developed by Gösta Holmér who experimented with the idea of playing with speed when training Swedish athletes to try and break the dominance of rival Finnish distance runners in the 1930s.

Fartlek training can improve your pace substantially

In short, a fartlek session consists simply of periods of fast running and sprints mixed in with periods of slower running and jogging. Starting with this basic principle, fartleks  can be adapted and tailored for a variety of training needs, running abilities, and fitness levels. And the best thing, by constantly mixing up your pace, going from sprints to jogs to hard paces, you’ll be hitting each of your aerobic, lactate and ATP-CP systems during the same session.

Next time you go out on your regular running route, instead of running at a steady even pace, try alternating between a jog, a fast run and a sprint across the duration of the run. You can use regular landmarks – say, lamp-posts or trees, park benches, whatever you want. Try and keep up the pattern for as long as possible but if you start to feel the pace a little you can always throw in an extra bit of jogging  – maybe jog for two street lamps’ distance instead of one or follow a jog-run-jog-sprint-jog pattern.

Replacing a regular short to medium length (3 to 5 miles) run once per week will help you avoid a training plateau, tune up your speed / race kick and get you much fitter per total minutes spent running than a standard comfortable paced run. And the more you do fartleks, the more you’ll notice your pace getting quicker as your body gets used to running at higher intensity levels.

But don’t just take my word for it – give it a go yourself and tell us what you think!

Need help with your training? Book a training session with Run Barca.