Interval training – The what, how and why

Nov 30, 2019

Ever notice how much runners and coaches love to use jargon? When it comes to interval training there’s seemingly no shortage of it. In fact, it can be downright confusing even to those of us supposedly well versed in the parlance. No surprise that confusing jargon has developed among coaches in categorizing or identifying daily training sessions. Sometimes you will hear or read about “cut-downs”, but there aren’t any scissors involved. Maybe you’ve heard of “breakdowns”, but we’re not really breaking down the runner (ha ha). There are also things called “Go’s” where after a specified recovery time the runner begins the next run. There are “Ladders”, “Clocks”, “Pyramids”, “In’s-and-out’s”, and “Repeats”, “Alternations”, “Bottom-ups”, “Top-downs”, and “Bends”. These are all variations on the theme of alternating runs with rest periods. Further confusion occurs between middle-distance and long-distance coaches. For example, some use the term “interval” for the distance run, but others consider it the recovery time between runs. It’s not necessarily a matter of right or wrong, but more an issue over consistency or inconsistency depending on how you view it.

The Basics

Man sprintingWanting to keep things simple and basic, here is the basic terminology. Running a specific distance for a specific period of time is the interval of running. Chances are you’ll do this several times. Several intervals of the same distance are referred to as repetitions (reps). Following each running interval, a specified recovery time permits a varying amount of rest, either complete or incomplete. Groups of intervals are called sets, and the recovery time between sets is generally longer than the recovery time between runs within a set. Finally, each run is performed at an assigned velocity (specified pace). If the athlete is running as fast as possible that is considered maximal pace. If it is slower than maximal pace it’s submaximal pace, plain and simple. (Martin, Coe; 1997)

Purpose of Interval Training

The primary purpose of interval training is to maximise aerobic power (VO2max). As we know from the principles of training and specificity, the best way to improve any bodily function is to stress that function. Therefore, to optimise VO2max, the runner must stress the oxygen delivery and processing system to its limit while performing the act of running. So, if you want to improve VO2max, the intensity has to be at or very near VO2max (and maximum heart rate) and the work-to-rest ratio has to be optimised to serve that purpose.

It’s been determined through research that a person can run at VO2max for about 10-15 minutes. However, it’s not desirable to make work-bouts at interval pace last that long. It’s also important to consider that it takes the body about 90 to 120 seconds to build up to VO2max from a complete recovery state. That being said, 3 to 5 minutes is considered a good amount of time to spend running at interval pace. Going for longer than 5 minutes would be too demanding because it is hard to run at 3k to 5k “race pace” X number of times when each of those runs lasts more than 5 minutes. It should also be noted that by not providing too long of a recovery period between hard runs, VOwill not have had a chance to fully recover, which allows the next work-bout to reach max VO2 in a shorter period of time (it will now take less than 90-120 seconds), which is an important determinant when using work-bouts shorter than 2 or 3 minutes. (Daniels, 2014)

In classic interval fashion, most runners, over time, will strive to shorten the recovery period between reps or sets. However, depending on the intensity and duration, if you rush the recovery too much, things happen, such as:

Because your anaerobic system can contribute energy for only a few minutes at the effort level required by “very intense” run intervals, without a full recovery between sets, you’ll overwhelm this system (the work-bout becomes too anaerobic), and your faster fibres will shut down, causing you to depend more on the aerobic system. When your faster fibres begin to shut down, you’ll slow down and rely more heavily upon your slow-twitch fibres (the work-bout then becomes too aerobic). Since interval training isn’t an effective workout for slow-twitch aerobic development, you’ll defeat the purpose of the workout.

Some caution is also advised when performing very high-intensity reps as these can overload the nervous system. The high-intensity force required by such intervals requires a sufficient recovery between reps to allow your nervous system to reboot.

Some Guidelines

You may have heard of Coach Daniels. He holds a PhD in exercise physiology, is a two-time Olympic medalist in the modern pentathlon and has over 50 years of coaching elite and Olympic athletes. The following six criteria are derived from his book “Daniel’s Running Formula”.

  1. Run intervals of between 30-sec and 5-min duration.
  2. Stick to the Interval Pacefor all aspects of quality running (for most runners this equates to 3k-5k race pace).
  3. Run easily during recoveries.
  4. Keep recovery periods equal to or shorter than the work-bouts they follow.
  5. Let the quality portion of an interval session total up to 8% of your current weekly mileage with a non-negotiable upper limit of 10km.
  6. Allow sufficient time to recover so that you feel you can perform the next interval as well as you did the previous one.

Daniels describes the Interval Pace as demanding or hard running, but does not involve all-out running. Daniels also warns that completing intervals at too fast a pace is of no value as the results will be no better than if you had run at the designated pace. In addition, the excessive pace will probably prevent full recovery before your next quality training session. Intervals are without doubt the most demanding training you can do, so you must never do too many. So folks, when you are out there on the track, try to leave with a little left in your tank for next time.

Mike McKnight

Coach Mike is the Owner/Coach of Running Workx LLC in California and a seasoned ultra-distance runner. He has certified coaching qualifications in endurance running, track & field and long distance running.


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