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Go Faster By Doing Interval Training

Interval training is arguably the most effective way to improve your racing performance over almost any distance in any endurance sport.


There is no doubt that in order to get the most from your training, it’s not enough simply to go out and do long slow distance. Swimmers have recognised this seemingly forever and it would be weird to find a swimming club that simply does a 4km straight swim every day.

Running clubs grasp this too, although a lot of road runners never do any interval training, other than the occasional fartlek interval. Cyclists might throw in the odd effort up a hill, work to catch another rider in the distance (which usually takes longer than expected) or occasionally chase an inconsiderate motorist, but structure is often lacking here too.

If we’re going to make intervals a part of our training, we need a bit more information, so here are some thoughts.

How long should my work intervals be?

This is an age-old question and depends somewhat on what your goals are. There are even a few different ways to achieve the same goal and I’d encourage you to think carefully about what will work for you. Remember, you are an experiment of one, what works for someone else might not work for you.

I’m going to discuss this in the context of endurance performance this time, but I’m sure to write a post in the future about higher intensity stuff. Many of the principles are the same though.

In the cycling world, the most popular threshold interval training is something lovingly called the “2 by 20”, two intervals of twenty minutes each at threshold (the level you could ride at for about an hour as fast as you can) with 10 minutes easy pedalling recovery between sets.

Apparently, they work very well, but not for me and not for most of my clients. The reason is that they’re simply too long for sustained focus and for most people unless you're in a very motivated state of mind you're unlikely to finish the workout. It just hurts too much.

I opt for a different approach, which is arguably more effective. Assuming I want the same volume, instead of 2 x 20 minutes with 10 minutes rest, I go for something along the lines of 10 x 4 minutes with 2-minute recovery (reducing the recovery to 1 minute after a few weeks).

I have no lab data, but I reckon the result is the same, if not better. Among other things, I will almost certainly finish this workout and consistency is key after all.

There are other benefits to this interval training approach too...

• Better movement quality throughout the workout - inefficient movement shows up both as injury in the long term and a higher energy requirement when you’re racing.
• A higher overall cardiovascular fitness benefit - you don’t recover fully between intervals and therefore your overall output for the workout is higher.
• Mentally you reinforce that this is a manageable intensity.
• A reduced risk that your central nervous system will feel threatened - having your central governor down-regulate everything or worse cause you to have to stop (“fail”) is a great way to stall your progress.

How long should my recovery intervals be?

As a rule of thumb, you want to start with recovery intervals that are twice the length of your work intervals if you’re not all that fit or are not used to interval training. Once you can achieve that easily, work your way down to an equal work to rest ratio and eventually to a point where your work is twice the length of your rest periods.

What is important is that if you were doing 6 intervals, the last one should be as good as the second one (the first one is often too hard, it’s called enthusiasm).

[Remember, we’re talking about long endurance performance here, so interval training at threshold intensity. If you’re doing sprints and doing them properly, you might need 10 more minutes recovery in order to maintain the quality.]

An advanced option for recovery periods is to use a “go on…” interval. In this approach, you decide on how long the combined work and rest should be, set that number into your watch and start the next interval whenever the time runs out.

This works very well where the pace is an issue (swimming and running), intensities are slightly lower and when rest intervals are short, for example when working on your race pace for a 1500m swim. If your target time is 25:00 and you were swimming 30 x 50m, you might set an interval of 55 seconds, aiming to touch the wall in 50s every interval.

This works, because the short rest allows you to maintain efficiency better than if you simply swam a straight 1500m. However, the rest is not enough to get much cardio-vascular recovery and the intensity remains fairly high.

The caveat is that you have to be consistent with pace: If you swim too slowly, you get no rest, if you swim too fast, the rest is not enough for you to continue the set beyond one or two more reps.

How many intervals should I do?

Here, more is not better. The correct answer to the question is: Do enough to cause the adaptation and no more.

Knowing how much is enough is a bit tricky, but you’re always better doing less rather than more. In many cases, just one or two short intervals are enough. If you get to the point that you’re fighting to finish, you’ve been too ambitious.

Somewhere between five and eight 400m repeats are more than enough to improve your running speed for a marathon, there is no need to do 105!

Earlier, I wrote about cycling threshold intervals. I actually favour 3 x 8 minutes for these, reducing my rest intervals to just 1 minute as fitness improves.

And my favourite swim set is 20 x 100, swum on a very short interval that allows about 5 seconds rest.


There’s so much more to write on this subject and this has already been rather long, so another post about intervals might have to follow soon.

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Will Newton

In over twenty years of coaching, I have coached everyone from absolute beginners to world champions.
My interest in getting the best results for people who train for health and fitness or the love of sport, rather than as professionals, drives me to find the most effective ways to get results.
My mission is simple: Be in better shape at 70 than most people are at 20, and to help you do the same.

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