Periodization, the systematic planning of exercise and athletic training. It is one of the cornerstones of high level sports and physical performance and without it, training has no context and no direction.

This series will cover the big picture as well as dive into the small nuances of what makes periodization such an important topic to learn for any aspiring strength & conditioning coach or high performance trainer.

This fifth installment will discusses the complexities of periodization and what to take into account when reading research about periodization.

Read Part 101: Introduction
Read Part 201: Training Variation
Read Part 202: Training Effect & Phases
Read Part 301: Review of Periodization Models
Read Part 401: The Complexities and Problems of Periodization Theory

Unanswered questions about periodization

So far, we've discussed the history of periodization, specifically how it came to be and why it was needed. We've also covered the physiological basis behind periodization and how training effects and variation play a role in creating a yearly and monthly plan for competitive athletes. Lastly, we dissected various periodization models and determined their defining characteristics.

On the surface, it may seem like these periodized training variables are already set in stone and backed by science, and athletes can achieve their best performance results just by following a strategically-written training program. However, there are still many unanswered questions about periodization:

Variation is needed, but HOW MUCH is needed?

What is the best periodization model for this sport ___?

What is the best periodization model for this athlete ___?

What is the best tapering/peaking method?

Does performance improve because of periodized and strategically planned variations, or simply because of a novel training stimulus?

How do you utilize periodization with your clients and athletes if you're... a high performance coach? A powerlifter? A personal trainer? A weight loss specialist? A dietician? A sports nutritionist?

Does periodization even matter to you? Should you even care?

Problems and limitations to the theory of periodization

Periodization philosophy is largely based on the fact that adaptations to physical exercise can be predicted and that it follows a determinable pattern, which can be problematic. The genotype-VO2max related Heritage Family Study as well as other studies looking at resistance training-focused interventions show several examples of how one exercise protocol can result in a wide range of responses in different populations and different subjects.

In the Heritage Family Study, an endurance training protocol was able to increase the average VO2max of the subjects by 19%. However, 5% of the participants saw no change in their VO2 values, while another 5% saw an increase of up to 50%. In a resistance training intervention, 12 weeks of a strength training program saw a 54% average increase in strength. The "non-responders" saw no increase in strength while more highly sensitive responders saw a 250% increase. 250%!!

Training adaptations are not only mediated by the training program itself (assuming adherence to the training protocols are close to 100%), but by other factors such as initial training age of the subjects, nutritional and dietary habits/protocols, recovery and restoration of the athletes (are they sleeping enough?), and exercise technique.

Initial Training Experience and Age of the Subjects

Like I alluded in the earlier articles, the initial fitness or training experience of a subject plays a factor in the results we expect to see after prescribing them a training protocol. Because novice and beginner trainees have low initial functioning performance measures, research studies focused on periodized training programs are unable to discern which periodization model works better for this population. When you're a beginner, almost everything works!

For example, in the realm of concurrent training (strength and endurance training together and their interaction), untrained individuals are usually able to increase both their strength and endurance performance with minimal interference between the 2 modalities. Trained individuals on the other hand, experience a greater interference effect when performing concurrent training: endurance training diminishes the adaptations of their resistance training and vice versa.

Nutrition and Dietary Protocols, Recovery & Restoration.

Nutrition has a large impact on training outcomes and adaptations. The fact that some strength, endurance or periodization studies don't account for dietary intake is problematic. For example, if protein intake is not controlled for in subjects of a strength training based research study, no amount of program-periodizing can come to any consistent conclusions about periodization and muscle strength or hypertrophy. I've written about nutritional periodization in detail here - check it out.

Recovery and rest obviously play a big role in the training process as well as it directly affects training performance, fatiguability of the athlete, and at the end of the day, determines how much progress they'll be able to make.

Exercise Technique

This is a variable that is often overlooked in research studies looking at the effects of periodization on strength in particular. Athletes and subjects that possess more biomechanically efficient lifting technique have a higher ceiling for strength acquisition, therefore may experience greater strength gains on any given training program. Subjects that are inexperienced, or have glaring flaws in their lifting technique are not able to reap in the full benefits of a periodized plan as their technique acts as a bottleneck for progress.

There is no quantitative way to assess lifting technique, therefore it is a variable that is hard to control in a research setting. I'm a firm believer that the execution of the lift, or of training itself, is very important in order to get the most out of a training plan.

Due to the practicality and perhaps lack of research funding, many of these variables I've discussed above are not taking into account when researchers design a study looking at different periodization models. Take these research study results with a grain of salt and remember: principles are always better than rigid, inflexible methods and systems.

The Complexity of human performance

As you can tell, the reality of human biology is very complex, much more complex of that of a car, a phone, or a computer. Despite what we know about exercise physiology and exercise science, strategic and well-planned training inputs into a human biosystem does not always ensure consistent predicted outcomes. As a consequence, performance, a multidimensional phenomenon comprised of physical, psychological and emotional factors, is hard to predict.

How much adaptation and how much progress an athlete makes from a training program can vary depending on an individual's hormonal response, genetic predispositions, motivation, stress levels, as well as transient social and environmental variables like the ones listed above. John Kiely, a respected coach and researcher, suggests that there must be great care taken when attempting to use isolated examples of athletes or periodization methods when trying to create an intervention or training program. In some cases, an athlete may have performed successfully despite a strategic periodized program, rather than because of it. This is a matter of recognizing confounding variables and avoiding falling into cognitive biases. Critical thinking and questions should be put forth during any periodized program: What are the individuals that don't see results doing differently? What confounding variables are we overlooking that have contributed to the success of an athlete or team other than the periodized program?

"Periodization Paradigms in the 21st Century: Evidence-Led Or Tradition-Driven?" by John Kiely (2012) is one of the top 5 most important articles on strength & conditioning and fitness I have ever read. Kiely shares a unique perspective on the complexities of periodization and is able to articulate points I could not have put my finger on. I highly recommend you read it when you get a chance. I have summarized some of his ideas in my article but have also added some of my own.

Another article I suggest is a 2017 review by Afonso et al, titled "Is Empirical Research on Periodization Trustworthy? A comprehensive Review of Conceptual and Methodological Issues".

Modern advanced monitoring tools such as blood lactate measurements, heart rate variability and GPS-tracking technology are also becoming increasing popular, further guiding the scientific basis behind sports and exercise planning. Despite all these advances though, human performance can still run an unpredictable course. Kiely uses the analogy of Earth's weather prediction system: although climate and space technology are very advanced, weather on the smaller scale is very complex and still unpredictable. *Related - If you've never heard of the Chaos Theory or Butterfly effect, here is some information on it.

This is not to argue that templated periodization programs do not work, rather, proper monitoring of athletes and on-going manipulation of variables should be emphasized and used in conjunction to suit the individual athlete or team. Periodization methods are not set in stone and models are not used exclusively. Some coaches may believe a certain periodization model is superior, when reality their methods are based off of a combination of different models.

With all that said, let's revisit the definition of periodization.

Previously we said: Periodization is the systematic planning of exercise and athletic training.

A more suitable and all-encompassing definition: Periodization is the systematic planning of exercise and athletic training, including the ongoing process of measuring objectives, outcomes and altering methods in the face of emerging information.

Applying these principles of periodization can be as simple, or as complex as you want, or need it to be. We'll be talking about the application of periodization in the next article.

5-Part Periodization Series Links:
Read Part 101: Introduction
Read Part 201: Training Variation
Read Part 202: Training Effect & Phases
Read Part 301: Review of Periodization Models
Read Part 401: The Complexities and Problems of Periodization Theory