Summary of my interpretation of “intermittent” training
Before continuing, let me explain what intermittent training means to me; it is my own interpretation, and explains what I see as the difference in methodology behind each form of intermittent training.
It has become apparent to me from what I have read over the years that I differ from many “experts” when discussing intermittent training. I feel therefore I need to explain some basic definitions so that when I go on to discuss any particular form of intermittent training it will be obvious what I am referring to.
Definition of intermittent training
Intermittent training is a generic “umbrella” concept that covers any type of training that does not have a steady or continuous pace as its main design. It is used in describing fast/intense periods of time/distance interspersed with other periods of time/distance made up of inactivity/complete rest or runs of a slower intensity/active rest.
Such training is sometimes referred to as, “In-Out”. At this point it does not really matter the type of running surface, the training format, the total distance, the number of sets and so on.
Let me make one initial distinction between types of intermittent training.
On the one hand we have predetermined intermittent training in which one, some or all of the elements are fixed: could be the pace, or the number of sets, the total distance, and so on.
Interval training (and please read later what I mean by that term, because it is not what many others mean when they use the term) is a perfect example of a predetermined workout.
On the other hand there is “spontaneous”, not-predetermined intermittent training. This might be considered more “chaotic” (in the sense of Chaos Theory, rather than simply meaning disorganised).
Fartlek in the “natural style” might be a perfect example. But a natural fartlek, where no set pace is determined, no number of sets, nor distances run, nor set duration of distance/time run before changing from one pace to the other. Basically you run “by feeling”, rather than to any calculated design template.
Actually the word fractional and the word repetitions or fractional/repetition workout it means different things to different coaches and runners. For me fractional it simply means the notion of “division” or of “fraction” and repetition it simply means “to repeat”.
Fractional training it comes from one primary concept of intermittent training is that it is a workout formed by cutting or dividing a race distance into a number of smaller parts (e.g.: 5-10 x 1,000m for a target 10k event). Each set distance is then run while you try to maintain a running velocity close to the race pace. The aim is to “repeat” the same distance over and over again at near race pace with a suitable recovery interval in between.
Organising the workout this way has proven to be an effective method of allowing running at race pace.
Early on, before the introduction of the interval training concept, the recovery was simply a pause long enough to allow a number of repetitions to be run at the same (near race) pace.
Therefore, when we discuss repetition workouts, the prime focus should be on the running pace, the recovery interval is of secondary importance. The recovery interval is solely to allow the runner to have a near-complete recovery between repetitions. To allow the runner to manage to run (a number of times) at close to race pace, the number of reps is always determined by dividing the target event.
Naturally, longer distance reps are utilised when the target is a long distance event; (e.g.: 6-10 x 1000m or 3-5 x 2000m for a target 10k race). While in middle distance events the repetitions tend to be shorter (e.g.: 7-10 x 500m or 4-5 x 1000m for 5k run and 4 x 400m or 2 x 800m for the Mile).
With the development of the repetition method, and the development of intermittent concepts in various formats and for different purposes such as those based on physiological concepts, or experience, or trial-and-error, the original concept behind repetition training has been changed.
Actually the repetition workout concept is more flexible. There is no longer a need to cover the total event distance in reps; longer reps can be done by time rather than distance, and repetition training has become merged into a generic “interval” training commonly used by long distance runners. But in my opinion the major change in the repetition workouts is that is used a pace that is different or faster than the race pace, it is more a “best” pace for the total repetition units. E.g.: a 3:45 1500m runner instead of do 5 x 500m 1:15 race pace does 5X500m quite all flat out faster than 1:15 race pace and delay the rest periods to allow a complete recovery.