Strength and conditioning practice has four key principles, which are progressive overload, specificity, individuality, and variety. Almost all research and coaching practice supports these principles, and while they are not fundamental laws, they are exceptionally good guidelines.
Periodization is one way in which the principle of variety can be applied to an athletic development program. Yet, if you asked a dozen strength coaches for their definitions of “periodization,” you would probably get thirteen answers. Consequently, there are a lot of arguments over what the term really means.
Fortunately, we can cut through some of the fog, since there are several ways in which we can define terms like “periodization,” which are not immediately clear from the outset.
The main ways that I have seen periodization defined are (1) normative, (2) teleological, and (3) descriptive.
#1. Normative definitions
This is where we argue about how the word “periodization” should be defined.
In order to figure this out, we obviously need a yardstick to measure against. The two most common yardsticks are (1) historic precedent, and (2) the way in which the term fits into our a training philosophy or framework.
When arguing about historic precedent, we tend to refer back to those coaches who originally coined the term, and what we believe they intended when they wrote about it. The problem with this is that we are not mind-readers, so will never really know what was truly intended at the time.
When defining the term to fit into a training philosophy or framework, we will always define it in such a way as to fit our preferred way of thinking, and this often fails to fit with the frameworks preferred by other coaches.
Most people tend towards arguing about normative definitions, without knowing that this is what is happening. This is why there is never any resolution, since we are arguing about either (1) something that requires us to be mind-readers, or (2) a preferred training philosophy, and not the definition of the term “periodization” itself.
#2. Teleological definitions
This is where we argue about what the purpose of “periodization,” by reference to what it is supposed to achieve.
For example, many researchers and coaches have noted that the purposes of periodization are (1) to improve performance, and (2) to reduce the risk of overtraining.
While it is useful to know what a training approach is supposed to achieve, it does not tell us anything about how this is done, or how we can tell whether a training program is periodized or not.
This type of definition is primarily only valuable insofar as it provides a standard against which we can measure whether periodization is actually doing what it is supposed to do, when we implement it.
#3. Descriptive definitions
This is where we try to determine how the majority of people are *actually* using the term in practice.
Descriptive definitions require us to figure out the commonalities between the usages of the term among many, quite diverse groups.
In doing this, we can arrive at the key features of what most people think of as “periodization,” and these features can then be bolted together to create a working definition of what the word means in conversations taking place in the real world.
By creating a good descriptive definition, can define the term that we call periodization, and this might not be the same thing as the definition that the research groups working on the problem might want to use.
Which type of definition is best?
As you can probably imagine, these definitions can sometimes be very different from one another. Yet, none of the ways of defining terms is superior to the other, they just provide different information, and are useful in different situations.
When we have a descriptive definition, we can talk about how periodization is used as a whole within the industry. In contrast, normative definitions cannot be used for this purpose, since they describe a theoretical construct, and not the reality of what is happening in practice.
On the other hand, normative definitions are useful when we are trying to figure out the underlying biological mechanisms of how periodization affects training adaptations.
In practice, few people declare upfront which definition they are using.
Most research papers tend towards using a normative description, although by referencing other viewpoints in support of their terminology, they can sometimes bring in descriptive elements, which is unhelpful.
In contrast, John Kiely, whose periodization review is probably one of the most important contributions to strength and conditioning of this decade, is more rigorous. He starts by clearly noting that there is no agreed formal (i.e. normative) definition, and then moves on to look at the commonalities of what is termed “periodization” in practice (i.e. to create a descriptive one).
In his review, John looked at a range of periodized programs to identify commonalities between them. For this article, and to provide a different perspective, I am going employ the mental model of inversion, and look at how non-periodized programs differ from periodized programs.
What are the key features of periodization?
Some popular strength training programs can be summarized in a couple of lines of text, including a few exercises performed for the same number of reps and sets, in the same three workouts every week. These programs are almost completely without variety, and the only thing that changes from one week to the next is the load on the barbell.
Periodized programs differ from these simple programs, since they incorporate variety.
Yet, the incorporation of variety cannot be the sole feature of periodization, not least because strength and conditioning already has a principle of variety, and there is no need for two terms to describe the exact same concept! More importantly, there are other ways of incorporating variety that are not always described as “periodization” in the industry.
Indeed, some bodybuilders train purely instinctively, doing whatever they feel like doing when they arrive at the gym. From an outside perspective, their training program is random, at least insofar as no framework can be used to describe its order. There are also some popular training methods that involve seemingly random workouts for people to do on a daily basis.
While these approaches incorporate variety, few people would categorize either of them as periodized.
Additionally, some very popular training approaches provide daily workouts for people to follow, which cover different fitness qualities, and which appear to be random from the outside. Again, I suspect that very few people would describe the sequence of these workouts as periodized.
Inverting this, we can say that periodization involves non-random variety, and not random variety.
#3. Planning in advance
Autoregulation is a technique that introduces variety into a strength training program, based on tests that are performed within a workout. The outcomes of the tests determine certain features of the workout for the day, based on predetermined guidelines.
It is true that some researchers *have* referred to autoregulation as a form of periodization, which I find quite strange. I suggest that most people in the industry instinctively see the two concepts (autoregulation and periodization) as different, because autoregulation does not plan the exact content of each workout in advance, but leaves it open to change, based on the circumstances of the day.
Inverting this, it seems to me that periodization involves planning the content of individual workouts in advance.
Finally, at least one well-known bodybuilding program recommends continuing with an exercise in the same rep range until progress fails for more than one workout. At this point, the exercise is switched for another that works the same muscle group, and the process starts again. This technique is not normally described as periodization, and this seems to be because it does not timetable the switch in the exercise in advance.
Inverting this, we can say that periodization involves advance timetabling of changes to workout content.
What is a *descriptive* definition of periodization?
From the above analysis, we can deduce that periodization as it is actually used in the fitness industry incorporates variety into training in a way that has three key features:
So if we wanted to derive a *descriptive* definition of periodization insofar as periodized programs can be differentiated from non-periodized programs, then it would be “the incorporation of non-random, pre-planned, and timetabled variety into a workout program.”
How can we assess whether periodization make a program better? — part 1
One of the biggest problems when discussing training techniques like periodization is that most people ask misleading questions. For example, you will often find people arguing about whether “periodization” works, when what they are really discussing is whether “periodized training programs” have a beneficial effect.
A periodized training program can be said to “work” if it causes an increase in the desired outcome (maximum strength, muscle size, etc.). But most strength training programs will do that, so this is not a particularly useful question in and of itself.
We can only say for sure that periodization “works,” if incorporating non-random, pre-planned, and timetabled variety into a workout program causes a bigger improvement in our desired outcome, compared to programs that include 0, 1, 2, or 3 of these 4 features (i.e. variety, non-random variety, pre-planned variety, and timetabled variety).
Unfortunately, the periodization research is very limited in this respect.
How can we assess whether periodization make a program better? — part 2
Researchers have exclusively employed long-term training studies for investigating periodization, on account of the difficulty in identifying the underlying mechanisms of its effects.
This body of research has explored the effects of comparatively short periods (2 — 3 months) of periodized load and volume, in comparison to unvarying training programs.
Early research looked at the effects of gradually increasing the load (percentage of 1RM), and simultaneously reducing volume in a linear fashion over a couple of months. Later research developed this idea by testing different permutations of load and volume over similar periods of time.
Essentially, the literature has compared the effect of incorporating non-random, pre-planned, and timetabled variety (in the form of altering relative load and volume) into workouts with programs that incorporate none of the key features (the control programs are unvarying).
In this way, the literature largely tests the principle of variety, rather than the application of periodization.
How can we assess whether periodization make a program better? — part 3
To move forwards with periodization research, we need multiple, high-quality long-term training studies in strength-trained individuals exploring whether a periodized program is capable of outperforming at least the following types of training program:
- a randomly varying program
- a non-randomly varying program that does not pre-plan the content of the workouts (e.g. using autoregulation)
- a non-randomly varying program that does not timetable the content of the workouts (i.e. uses tests to determine when to move from type of workout to the next)
Even so, this would still ignore the various possible combinations of the four key features (since periodization requires all four), and would therefore only be a step in the right direction.
And we haven’t even got started on the effects of varying other training variables rather than just relative load and volume, such as exercise selection (which actually makes a lot more sense).
What is the takeaway?
Periodization can be defined in different ways. A descriptive definition of periodization summarizes the key features of periodized training programs as they are used in practice. Through the identification of four such features, periodization can be defined as “incorporating non-random, pre-planned, and timetabled variety into a workout program.”
Currently, the research has identified that incorporating variety improves the outcomes of workout programs, yet it is still unclear whether this variety benefits from being (1) non-random, (2) pre-planned, or (3) timetabled.
As John Kiely said several years ago now, the evidence to support the way in which most strength coaches currently go about periodizing strength training programs is largely derived from tradition, rather than science. That does not mean that periodization (as defined in common usage) does not work, it means that the research we need does not exist, and therefore we don’t know whether this thing that we call periodization actually produces better results than any other way of implementing variety.