Basics of interval training
Designing interval training sessions is one of, if not the most, fun aspects of being a running coach. Coming up with brand new ways to test the body, develop speed and strength, and build towards pace goals. Breaking runs down into more manageable chunks can enable runners to hit specific paces (5k time) and training zones (such as VO2 max, lactate threshold etc) and the variety can break up the miles. In short, you need interval training to get faster, fitter and stronger – whatever distance you run.
The purpose of intervals
Interval training wasn’t always the way to approach running. 100 years ago (think Chariots of Fire and the previous Paris Olympics), continuous running over different terrains was the preferred method. [1] That changed in the 1930s with the creation of the fartlek run, an informal form of interval running based on feel. Then, a German physiologist (Reindell) and coach (Gerschler) created the system of running we know today as interval training. They were focused on the cardiovascular aspects of running, noting that the recovery periods in between sets enabled the heart rate to decrease. In turn, this meant the heart temporarily increased its stroke volume, which made it stronger (and you fitter). [2]
I include this brief history lesson not just for us running geeks – and the opportunity to reference Chariots of Fire – but because of the key part of how interval training started is the key part we often forget: the recovery portion.
Picture the scene. You’re working on your 5k/10k pace and have read that 10 reps of 400m is a good session. You want to focus on your speed – and your VO2 max – so you’ll take a 2 minute recovery to get your heart rate down. Then it starts raining, so you run a 400m and rest for 1 min 15, then you rest for 45 seconds, then you run one a bit fast so give yourself 2 mins 30. Then you realise you’re late, so do a 400m as fast as you can then go home before doing the last one. Sound familiar?
While increasing your work rate by introducing speedwork will broadly always help challenge your body, putting the effort into a 10 x 400m (or 9 x in this runner’s case) should equate to maximum reward. Haphazard approaches where you work a little bit of everything does just that: work a little bit.
Every run has a purpose. Even easy runs have a purpose. But particularly with interval training, you need to know what you are working on, and where you’re at, to achieve what you want to do. In our example above, depending on their speed, our runner could have hit pure speed, VO2 max and lactate threshold all in different parts of the same session.
There are thousands of different combinations of interval training, depending on your goals, your running and your preferences. This is why there are so many training methodologies, as coaches have learned to refine their own systems based on the runners they coach. There also hundreds of purposes runs could have. So while our runner wants to focus on all of those elements - speed, VO2 max, and Lactate Threshold – they want to do so in a systematic way which works all three, as opposed to making an interval soup.
Demystifying interval training: DIRT training
While interval training has developed into a modern art and science, this 2001 article from Runner’s World sets out the four basic principles of classic interval training which provider a useful framework for designing sessions. [3] And it’s all about DIRT.
D - Distance
These can be anything from 50m sprints to 2 miles tempo sections.
I - Intervals
The recovery portion. Can be standing, walking or light jogging and can vary from seconds right up to 10 minutes, depending on the purpose of the session and the training stimuli sought.
A note of caution. The article referenced here says:
“One of the original principles of interval training that is still generally accepted is that the next repeat should not begin until the athlete’s pulse has dropped to 120 beats per minute”.
This takes no account of your own max heart rate, most notably impacted by age and gender, so while it is good practice to check your heart rate to see you have recovered “sufficiently” (depending on what your aim is ), don’t use an arbitrary 120. Aim for 55-65% of max HR instead.
R - Repetitions
This is the number of sessions you do, which can be broken further down into sets. For instance, you might do 6 x 200m with a 1 min rest between, then take a full 3 minute break before doing 4 x 800m.
T – Time
Time is the foundation of pace. How long you take to run 400m (e.g. in 2 minutes) will be the same as running @5k pace (e.g. 9:22 min/mile).
Physiologically the time is what counts, the pace per distance is simply the calculation. Psychologically however it can be helpful to run at set paces. You become more confident that you can run a longer distance knowing you can hold paces over shorter intervals. Again, it depends on (wait for it) the purpose of the session.
BONUS!
H – Hills
Hang on, DIRTH isn’t an acronym. And it’s true, hill training is not included in this classic outline. Most of the time, the same principles of DIRT will apply to flat or hills. So a 6 x 30 seconds @ 5k effort pace with a recovery down the hill fits this approach entirely. Where an added variable can be added to the mix is gradient, as our session there will feel very different on a less hilly hill than a hillier...hill. Both are important as part of a well rounded training regime, although hillier races will require hillier work. I.e. depends on your goal.
Having a coach can help demystify some of this and ensure that the effort you are putting in leads to the impact you are seeking. They can assess where your strengths and weaknesses are and come up with options for you and your goals. But even without a coach, use the DIRT approach to ask yourself: what is it you are trying to achieve and what variables can you alter to get there?
[1] A Brief History of Interval Training: The 1800’s to Now – Science of Running
[2] How Interval Training Started – Dr. Jason Karp (drjasonkarp.com)
[3] A Guide to Interval Training | Runner's World (runnersworld.com)