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Interval Training For Runners: Get It “ON”

Intervals – you either love them or hate them. Which side of the fence do you live on?

There are various flavors of intervals but the version I am referring to are the those intense, high effort, short duration intervals.  Yes, the ones that make you cry home to mamma!

I prefer long course events (marathon+) and always blew off anything that made me hurt in such a short amount of time. What’s the point? I need to run for 3+ hours in a race, not 5 minutes.

I am starting to come around that short and hard running may be worth exploring if you are interested in running faster in any distance event but one must have some yoda-like insight as well or it all is for not.

Running-Advice puts together the following video that adds some additional thoughts on the benefits of interval work for all race distances.

Desert Series Episode 11 – Speed work and marathon runners – a match made in Heaven? from Joe English on Vimeo.

(If you can’t see the video you can click on the following link.)

Note: Hard effort (VO2max / 98-100% Max HR / ~5km pace) intervals put the body under significant stress. Talk with your doctor if you are unsure of your current physical health. I also have been consistently running for a number of weeks/months establishing a base before including intense interval sessions into my training.

What are your thoughts on hard interval training? Are they a benefit to long course running?

Over the next few weeks, we will explore these intense intervals and look at some of my Garmin 305 data from recent intervals sessions and see what we can learn from it.

During this training block I am using Jack Daniels’ Running Formula to assist in determining my interval pace based off of a recent race result.

Why Hard Intervals?

Daniels mentions the purpose of hard intervals is to improve:

  • the  amount of oxygen that can be delivered to the running muscles
  • the muscle processing of the delivered oxygen
  • the muscle ability to handle waste removal (carbon dioxide and lactic acid)

Translation – run faster!

Do these potential benefits seem to be a prerequisite for short course runners only? Not really.

One other thing to be aware of is these intervals are hard and intense but controlled. Always try to maintain form throughout the run.

Determining Your “ON” Duration

This week my interval workout (first of training block) consisted of 4 X (4 min “ON” @6:39min/mile – 3 min “OFF”). After a two mile warm-up the graphic below displays the first three intervals in a heart rate vs. time graph. (Click on the image to see the entire graph.) This entire workout was done on a treadmill at 1% grade.

Garmin 305 Interval HR Data

Garmin 305 Interval HR Data (Click on image to see full data)

There are many things we could discuss from this graph but for this post let’s focus on the heart rate buildup and determining the “ON” duration of the interval.

With the goal of these intervals to stress our current aerobic capacity (by getting close to max HR but not above), it would seem fair to say that the desired goal portion of the workout is occurring when the heart rate stabilizes/flattens as this would appear to mean we have reached our maximum VO2 for this particular interval. It is this portion of the interval we desire.

So what’s the point?

If you look at the heart rate build up of each interval, it roughly takes around two minutes before the heart begins to stabilize/flatten and then the desired work begins.

Yes, so?

It would seem beneficial to run hard intervals with an “ON” duration greater than two minutes. As my heart rate chart shows, the approximately first two minutes are really just an appetizer for the main course. In order to get to the main course, you have to run longer than two minutes!

Daniels recommends performing intervals having an “ON” duration greater than two minutes. My data seems to match his research.

Daniels also recommends to not run longer than five minutes during the “ON” portion so that you don’t over tax the body and negatively affect upcoming training sessions. This would seem to be an individual assessment but it is probably a good recommendation to begin with. Have you ever ran longer VO2max intervals? What was your experience?

Also, the “OFF” portion time amount is equal or a bit less than the “ON” amount to allow a fairly full recovery between intervals.

What if you don’t want to run longer than two minutes during each “ON” segment?

If you like to keep the work duration short and frisky, it would seem beneficial to run the first interval’s “ON” portion for at least two minutes in order to reach the approximate maximum heart rate / VO2 for that particular pace but then greatly reduce the recovery/”OFF” time (Such as 50% of desired “ON” time).

For example:

  • Interval 1 – 3 min “ON” – 45 seconds “OFF”
  • Interval 2 – 1 min 30 seconds “ON” – 45 seconds “OFF”
  • Interval 3 – 1 min 30 seconds “ON” – 45 seconds “OFF”
  • etc…

From looking at my data sample of one, the “OFF” portion heart rate seems to stabilize in the same amount of time as the “ON” portion (two minutes). Therefore, starting at interval two, maximum heart rate / VO2 for this particular pace would stabilize in about 45 seconds which would provide 45 seconds (90 seconds – 45 seconds) of the desired stress for each consecutive interval.

How Many Frisky Intervals To Provide The Same Desired Stress As My Original Workout?

My original workout had two minutes of desired stress per interval (four of them) for a total of eight minutes.

To aquire approximately eight minutes of desired training stress using the frisky interval method, it would seem to require 11 intervals if using the above approach. [1 minute + (10 x 45 seconds) = 8 minutes 30 seconds]

Do you prefer longer (3+ min), shorter (less than 2 min), or mixed hard intervals?

Many Choices

The combinations of hard interval sessions are as many as you can imagine. Experiment and observe which method or combination your body best responds to. This is the fun of endurance sports – constant opportunities to explore and try and understand one’s self.

I am going to repeat the same original workout for two more weeks so it should be interesting to see how the data compares and even more importantly observe if it begins to translate into more speed.

Be active – feel the buzz!

David –

About the author

David Hanenburg David Hanenburg is the passionate dirt-lovin' creator of Endurance Buzz and has been playing in the endurance sports world since 2000 after knockin' the dust off of his Trek 950 hardtail thanks to a friend asking to go ride some local dirt. In 2007 he ran his first ultra on the trails and fell in love with the sport and its people. For more information on David's endurance sports journey, check out the About page.

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