Interval Training

Photograph: Lisi Niesner/Reuters

Have you ever been amazed at the speed of the leading athletes in a marathon or did you watch – awestruck – as Eliud Kipchoge ran the sub 2 hour marathon distance in one hour, 59 minutes and 40.2 seconds? Do you wonder how the top Tour de France cyclists reach those speeds in such gruelling conditions? Or have you just found yourself thinking about how you can improve your own time over a given distance? Clearly the top athletes have a genetic advantage, having the right body type for their sport and the right physiological make up for a prolonged high power output. But this is still coupled with the correct extensive approach to planned training, usually involving both high volume and high intensity training. But what about if you are not a professional athlete and are looking to improve performance over a given distance? The key is in the intervals…

What do intervals do?

Interval training has a sound basis in physiology and a good scientific grounding. If a runner was keeping up a 4 minute mile pace, a large portion of the energy would come through ‘anaerobic glycolysis’ meaning lactic acid levels would rise and result in exhaustion. During intervals however, repeated bouts of 10-90 seconds duration would allow a high training load to be performed without maxing out from lactic acid due to the brief recovery periods in between. In the example of soccer, the studies of Hoff & Helgerud showed that they could improve or maintain the aerobic fitness of a player with the following protocol:

  • 3 minutes at 70% of maximum heart rate
  • 4 minutes at 90-95% of maximum heart rate (getting to this zone within the first minute)
  • Repeated 4 times minimum (28 minutes total)
Br J Sports Med

During my time working with professional soccer and rugby players, this method was used extensively to help maintain player fitness during the off season and applied to base training modalities such as small sided games, to bring about sport specific adaptations to their fitness. I still use this protocol extensively with clients as it is specific to their level and always elicits an improvement.

Of course, intervals can also be programmed by using distances and working on ‘repeated sprintability’ (yes it’s a thing). For example, on a track you might perform 10 x 400 metres with a 150 metre walk in between . After the first 400m run you record your time and try to make sure that each subsequent 400m is no more the 5% outside of that effort. This does require a bit of practice however, as the aim is not only to run fast but to perform the same effort consistently – pace judgement is essential and is usually used with more experienced athletes.


There are arguably two important training concepts that more recreational exercisers invariably neglect in their quest for improved performance. These are:

  1. Working at a variety of different training intensities
  2. A periodised plan of training and recovery

If you are training frequently you will see results up to a point. Repeated training and recovery means the normal mechanism of Selye’s ‘General Adaptation Syndrome’ will take effect and will lead to an improved output by developing strength-endurance. But now imagine you have followed a carefully planned training programme with adequate recovery (or not, in the case of some interval protocols). The right training methods will maximise the “supercompensation’ component of your fitness and lead to an improvement in performance. This is something that has been studied extensively for years and it is now generally accepted that training needs to be of differing intensities to bring about an adaptation in your body’s ability to take up transport and use oxygen (VO2). Furthermore, the recruitment and adaptation of muscle fibre types alters with exercise intensity.

Selye’s General Adaptation Sydrome model.

So what are these intensities?

Let’s say there are 4 to 5 levels of intensity:

  • Level 1 is low intensity or recovery training
  • Level 2 is like ‘steady state’ exercise
  • Level 3 is at or around your lactate threshold (the point at which your body starts to work without oxygen and accumulates lactate)
  • Levels 4/5 are where you are working firmly in an anaerobic capacity (without oxygen)

Most recreational runners will usually train around level 2. But as you move up through the levels, if the duration of rest is insufficient enough to allow a full recovery, the athlete is forced to cope with increasing exhaustion, which helps develop muscular endurance and lactate tolerance.

Periodisation and your distance plan

The first thing you need to do to become faster, is a personalised schedule. Periodisation is the term given to the process of dividing the time between now and your peak performance (i.e. half marathon) into separate training phases, each with their own training emphasis. You are trying to maximise gains and specific aspects of fitness (i.e. speed/ speed endurance/ lactate tolerance etc). This also helps to reduce the chance of any ‘burnout’ from over-reaching or overtraining. If we look at running or cycling as an example you would have a:

  • MACROcycle – the time between now and your race
  • MESOcycle – several phases or blocks within the macrocycle (between 2 – 6 weeks depending on event and time)
  • MICROcycle – (usually a week) which is the detailed section of your specific volume, intensity, duration and sequence of sessions.
An example of a linear microcycle, showing 5 stages of progressively increasing load and one stage of unload/ deload

How these are planned will vary from coach to coach. The science is widely known amongst fitness professionals but how the science is used is the individual coaches “art”. One thing they can all agree on though – INTERVALS.

So… what’s the plan?

To improve speed over a given distance the plan is to fine tune your aerobic engine. You do this by working out whether you need to add volume or intensity, by having precise training paces to work at, and incorporating some resistance work and prehab to bulletproof your training. You can incorporate the concept of 3 key elements that form the foundation of the microcycle (weekly):

  • The long session – no brainer. Over the period of the training plan this builds up gradually to become longer and develops aerobic endurance by improving VO2 (maximum oxygen uptake).
  • The speed, hill and HIIT section – this adds challenges to the variety of energy systems used by the athlete (if you want to run faster – you have to run faster)! This means training the anaerobic lactate energy system (energy without oxygen) over a series of short intervals, hills or circuits. This also allows a specific strengthening of the legs whether running or cycling for example.
  • The prehab, flexibility, strength and conditioning session – this is important to avoid injury and to bulletproof the muscles that are undergoing a lot of repetitive mechanical strain. To finish first, first you must finish!

It’s important when prescribing intervals that it is monitored correctly (especially with beginners). Heart rate is a relatively accurate means of monitoring intensity. An appropriate range that accommodates most levels of fitness is from 40-85% or max VO2 or Heart Rate Reserve (HRR). Use HRR to calculate the appropriate target heart rates for interval conditioning. Of course, the easiest way to monitor is the tried and tested Rate of Perceived Exertion (adapted) or RPE (scale of 1 to 10).

High-Intensity Interval Training (HIIT)

It’s great because it’s simple! Short bursts of intense movement followed by a brief recovery period such as that outlined by the studies of Tabata:

  • 20-30 seconds “exhaustive” or ‘all out’ work
  • 10 seconds recovery
  • REPEAT 8-10 times over 10-20 minutes

HIIT has been a feature of sports conditioning for decades and is now more widely used. It increases short-duration strength-endurance with high intensity loads and the capacity to recover afterwards. You can do HIIT using a whole range of movements or equipment such as bodyweight circuit, run, cycle, skip – whatever your preference. It is an effective way of spiking your metabolism and a proven fat burner.

While there are many other factors that should be considered with training for longer distances, this blog is just focusing on the interval training aspect and I will cover other elements of endurance training in future articles.

Of course before taking part in any HIIT or other types of interval training, it is best to get the advice of fitness/ medical professionals for the appropriate prescription of a training plan. If you would like to know more about interval training or where it should be in your training schedule, feel free to contact us here. You can also contact us for a list of references used for this article.

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