Periodization 401: The Complexities and Problems of Periodization Theory

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

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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?

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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.

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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

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Periodization 202: Training Phases, Residual & Cumulative Training Effects

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 third part will discuss cumulative and residual training effects as well as the phases of training (off, pre, in-season).

~1800 words; 8-16 minute read

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

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Training variation recap

As discussed in Part 2 (201), training stimuli can be described to fit a general-to-specific paradigm, where specific qualities are movements, mental states and physical attributes that are seen in the sport or competition the athlete or trainee is preparing for; while general qualities are variations of sport-specific attributes that builds the base to allow specific qualities to flourish in the long-term. Along with this general-to-specific paradigm, some physical attributes and motor skills are thought to be better developed in a sequential manner; either from a general-to-specific or simple-to-complex paradigm. For example, muscle hypertrophy is thought to be better developed prior to maximizing strength and power potential while jump-landing mechanics are better learned before more complex plyometric drills.

The general-to-specific paradigm can be applied to various training and programming variables, from exercise selection, to intensity, volume and frequency. The amount of variation included into a training program differentiates one periodization model from another. Before we take a critical look at each periodization model, we have to understand training effects and the concept of training phases.

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Cumulative & residual training effects

If we run long miles, we build incredible endurance. If we resistance train in high volumes, we experience muscle hypertrophy. When we provide a training stressor, we adapt and experience a training effect. But how come we don't experience muscle hypertrophy right after a training session? How come it takes weeks of training in the 1-5 rep range to get strong?

Training effects can be categorized into: 

• Immediate and Acute effects (the immediate effects of training are: muscle fatigue, energy depletion, increased blood flow to working muscles, immediate changes on blood pressure and heart rate, etc)

• Chronic and Cumulative effects (increased endurance, muscle hypertrophy, increased strength and power, etc over the long term)

• Residual effects (to what extent training adaptations deteriorate after bouts of detraining or deloading)

For the purpose of this article, we'll be discussing cumulative and residual effects as it pertains to periodization and programming.

The cumulative training effect refers to the changes in "physiological capabilities and level of physical/technical abilities resulting from a long-lasting athletic preparation" (source). Vladimir Issurin, an expert and innovator of Block Periodization, notes that there are functional limits to our body's physiological systems, some of which are more trainable than others. Changes in aerobic characteristics from endurance training such as mitochondrial biogenesis and muscle capillarization are more pronounced compared to anaerobic characteristics such as hydrogen ion buffering. 

In contrast, residual training effects refer to how long these adaptations are maintained after an acute withdrawal of training volume load or absolute cessation of training. The table below shows the residual training effects of different physical adaptations: 

The degree of detraining is dependent on several factors.

First, the duration of training before cessation. Residual training effects usually follow an analogy made by Vladmimir Zatsiorsky (author of The Science and Practice Of Strength Training) and Dr. William Kraeme: "soon ripe, soon rotten". This suggest that physical attributes that have been developed for a longer time, can be maintained for longer before there is a decrease in performance following a deload or periods of no training. In a similar view, Nick Winkleman and Issurin note that adaptations that result from a structural change, such as cardiac remodelling, muscle capillizaration and muscle hypertrophy last longer after detraining, compared to adaptations that occur on the enzymatic level such as anaerobic performance,  hydrogen ion buffering and phosphocreatine storage.  A great example of this in the strength training realm and one that many of you can relate to is the fact that many lifters and trainees are able to maintain their muscle mass even with prolonged periods of low volume, high-intensity training. Muscle mass loss is a fear many bodybuilders and fitness enthusiasts have. But if you've spent some quality time building that muscle and protein intake during periods of deload are high, chances are, it won't waste away as quickly or as easy as you think. 

Secondly, the training age and experience of an athlete/trainee also plays a factor in training residuals. Older and more advanced level athletes tend to experience longer residuals because of their higher accumulated training time, in line with the "soon ripe, soon rotten" analogy.

Lastly, the intensity used during retraining or detraining loads plays a role in mediating training residuals as well. The use of moderate to high-intensity training  slows down the rate of detraining, however, volume must be controlled in order to avoid disrupting the recovery process. Residual training effects are of extreme importance especially when using non-traditional periodization methods like block periodization or when managing the training loads for sports team athletes during the in-season or competition-period. Residual training effects also give way to the method of tapering, where volume is decreased to reduce fatigue and allow for the expression of fitness (Fitness-Fatigue Model). 

An extreme example of this is a study carried out by Pritchard et al. 2017, where resistance trained males completed two 4-week training programs followed by either 3.5 or 5.5 days of training cessation. Following this deload (in the form of no training, NOT lowered volume), peak force in the bench press and mid-thigh pull increased above baseline.

Infographic Designed by @YLMSportScience

I will cover the concept of tapering and include some practical methods/recommendations in future articles. 

Since not all physical abilities can be developed concurrently in a periodized program to the same degree, knowledge on the cumulative and residual effects enables coaches to prioritize certain performance measures, allowing them to make better strategic choices when planning a training program. 

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Phases of Training

One of the most agreed upon definitions of periodization is the division of training phases and periods within a training macrocycle. However, the names of these phases vary depending ont he sport, characteristics of the periodization model, and the philosophy of the coach.

Mesocycles/phases commonly follow the names: preparatory phase, competition phase and transitional/active-rest phase. The preparatory phase can further be divided into general preparatory phase (GPP) and specific/specialized preparatory phase (SPP).

PREPARATORY PHASE/OFF-SEASON

In GPP, the training variables are more general and varied in nature, stimulating a wide variety of physical attributes while during the SPP, variables and movements are more sport-specific, aiming to further prepare the athlete for competition.

GPP and SPP can be further broken down into extensive and intensive phases, describing the average intensities of that particular phase. An extensive phase will primarily consist of low-intensity, high volume training, using 50-70% of 1RM during resistance training (muscle endurance and hypertrophy) and working in Zones 2-3 in endurance training (aerobic). While an intensive phase will include a larger amount of medium to high-intensity training using training loads above 75-80% of 1RM and high intensity interval training for conditioning.

The preparatory phase is often called the off-season in seasonal, team-based sports like hockey, soccer/futbol, rugby, etc. This off-season or preparatory phase is where the most aggressive and creative periodization strategies occur to induce the most improvements in performance variables before a competition date or competitive season. Any weaknessess identified from previous training cycles or competitive matches is best addressed here, and any strengths should be further improved.

TRANSITIONAL-1 PHASE/PRE-COMPETITION/PRE-SEASON

After a preparatory training phase and prior to a competition date or competitive season, the volume load of training starts to decrease. This decrease is meant to achieve 2 things:

• Reduce training fatigue so physical and mental attributes are peaked for the upcoming competition/season

• Make time and room to accomodate the upcoming competition schedule, travelling schedule, media obligations and hone in technical sport-specific skills

This phase is called the transitional-1 stage, or the pre-competition phase or pre-season phase. Because of the length of many sports' in-season (lasting anywhere from 4-7 months depending on playoff eligibility), team-based sports should avoid any aggressive tapering methods heading into the competition season, and a more strategically planned maintanence program should be prescribed. This differs from climatic sports like many sports in the Olympics or combat sports like MMA and boxing where the athletes are preparing for a one-day/one-night competition. In those cases, aggressive tapers are necessary as there is less of need to maintain physical attributes post-competition.

COMPETITION PHASE/IN-SEASON

The competition phase, also known as in-season for team-based sports, is dedicated to maintaining specific performance variables such as strength and anaerobic conditioning in order to attenuate any detraining effects an athlete or team may experience. Knowledge of residual effects really plays a big role here. A coach needs to know how many hypertrophy-based, strength-based, power-based and conditioning-based training sessions are needed in order to maintain an acceptable level of fitness when their athletes are busy competing in matches, games and tournaments. A coach must also take into account what physical attributes are already being trained just by competing and playing in games. This may differ from position to position depending on the sport. A goalie in soccer will not utilize the same energy systems as a forward, a post will not have the same energy expenditure as a point guard in basketball. The most time and energy-efficient method of maintaining physical attributes must be performed when athletes have a full competition schedule.

TRANSITIONAL-2 PHASE/ACTIVE REST PERIOD

The transitional-2 or active-rest phase of a yearly training plan is dedicated to complete restoration of the team and athletes, both from a physical and mental standpoint. It is common for athletes to engage in physical activity or exercises that do not relate to their respective sports. However, exercises should be low-impact in nature and should not impede or jeopardize the recovery process if high performance is the goal. The main goal of the transitional-2, active-rest period is to withdraw physical and mental stress and pressure that accumulated from hard training and competition, in order to avoid overtraining and mental burnout.

Rinse & Repeat

When the athletes have undergone adequate rest, they are now ready to re-enter the preparatory training cycle or off-season. These phases or seasonal compartmentalization of training occur on the macrocyclic level, with each phase lasting several months (depending on the sport, of course). There are a few exceptions, like in combat sports, where competition dates differ year to year, usually controlled by fighter rankings, and business-driven promoter decisions. In these sports, rigid periodization models often fail in properly preparing the athletes for competition; therefore a more flexible approach to periodization and training programming must be used. In the next article of this series, we'll dive into specific periodization models and their defining characteristics.

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

Periodization 101

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 first part will talk about the history of periodization and how the concept came to practice, as well as the true definition of periodization and the physiological basis behind physical training and planning. 

~1900 words ; 10-15 minute read

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

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Introduction To Periodization

Many articles posted online about training periodization revolve around how to set up your training to "bust through plateaus" and hit your "biggest PRs ever". While periodization certainly does help you in doing both, many authors neglect to write about the "whys" and are inconsistent when using training terminologies. What's the difference between linear and daily undulating (DUP)? What's block training? I thought blocks were called phases? How do I linearly progress man? A lot of terms get thrown around without proper context, and unless you have some background in exercise science or an in-depth understanding of exercise physiology, it can get confusing. To play devil's advocate though, there are many concepts and training methods that share different names; usually due to that fact that different researchers and difference coaches around the world use them and have made them popular in their own training niche or sport.

Quick example: tempo training in the world of running (tempo running) consists of a more fast-paced run usually right at an athlete's lactate-threshold. However in cycling, tempo training is done below anywhere from 10-15 beats below an athlete's lactate-threshold. What seems like a small adjustment can be the difference between increased endurance, or poor recovery and overtraining. This may be a specific example, but I hope you get the idea.

Before we even get into the types of periodization and how to manipulate training variables, we must know WHY things are set up the way they are. Training terminology must be consistent and training modalities need to be contextualized. 

With all that said, let's jump into it.

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The History Of Periodization

How did the concept of periodization come to fruition and why was it invented?

Sport training theories and methodologies have been developed throughout human history, dating back to the 2nd century AD, notably by Roman philosopher and physician Galen and ancient Greek scientist Philostratus. In order to achieve spectacular results and performances at the ancient Olympic games, these 2 gentlemen developed their own training theories which have laid down the foundation for contemporary training periodization.

Galen created the idea of building strength without speed, developing speed without strength, then using intense exercises to combine the 2 to create the most powerful athlete possible. Philostartus on the other hand, constructed the idea compartmentalizing training protocols:

"compulsory 10-month period of purposeful training followed by 1 month of centralized preparation... prior to the Olympic Games".

Sounds an awful lot like the off-season and in-season training camps of today, right?

Let's fast forward a few thousand years.

In the 20th century, the contributions from a factory supervisor named Frederick Winslow Taylor further paved the way for modern training management. As the founder of the "Principles of Scientific Management", Frederick believed there was a systematic way to organize and plan in order to achieve the best outcomes in the most efficient manner. The appeal for the scientific method came from several different driving forces: the fact that the explanatory power of the scientific method resonated with the society, and the ingrained human attraction for simplicity, rules and automatized solutions. What originally was a paradigm developed for the engineering and automobile industry, has given way to exercise and sports performance planning.

How do we achieve the best performance possible on any given date? How do we create a training system that works for a particular group of athletes? How do we improve performance given our current resources and limitations? 

These are the questions periodization attempts to answer for a variety of different sports, athletes and scenarios.

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Popularization of Periodization

"All World Records Shall Be Ours!" A Soviet poster from 1948.

The concept of training periodization was not developed on a large scale until the 1950's, where former USSR teachers, coaches and scientists called for separate training periods, general and specialized phases. These phases, encompassing the training of basic athletic abilities, cardiovascular fitness and strength, were applied in a sport performance as well as physical education setting. When numerous studies on exercise physiology and human biology were published to back these concepts, sport scientist Lev P. Matveyev compiled the massive amount of data. Matveyev is to this day, recognized as the founder of the traditional theory of periodization (commonly and wrongfully called linear periodization - more on this later).

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The definition of periodization

Although there have been several models of periodization developed since Matveyev's traditional model, it is widely agreed upon that the definition of periodization is the divison of training periods and the principle of cyclical training where programming variables such as intensity, volume, frequency, rest, and exercise selection among others, are strategically manipulated and varied in order to reduce the risk of injury and maximize sport performance for individual athletes or sports teams.

Periodization takes into consideration the level, training age and genetic predispositions of an athlete in order to avoid overtraining and allow them to peak for one or several competitions. In a periodized training plan, certain time-frames exists for the manipulation of programming variables, these time frames are termed macrocycle, mesocycle and microcycle.

A macrocycle is considered the longest duration of the training cycle, usually several months in length or even a few years. For example, a quadrennial macrocycle describes a 4-year long program used to prepare an athlete or sport team for the Olympic games. A macrocycle is comprised of several mesocycles, which are a few months in length and can be defined as a prepatory, competition or transitional phase. Lastly, mesocycles are further divided into microcycles which deals with training on the weekly-basis.

Macrocycle (months to years)

Mesocycles (weeks to months)

Microcycles (training on the week to week basis)

Using this definition, many popular strength programs that you and I are familiar with (Stronglifts 5x5, Texas Method, Starting Strength, etc), ARE periodized. Periodization does not imply some fancy, advanced, over-the-top program meant for elite athletes... although it can be. Periodization simply means your training plan is divided and organized in a way that makes sense and is in line with the nature of human biology and exercise physiology. The difference between a periodized program for a beginner vs. an elite athlete lies in the number of variables that are controlled for and manipulated. A weight training enthusiast can see results with the simple manipulation of intensity and volume, whereas elite athletes will need more advanced manipulation of loading schemes, exercise selection and nutritional intake in order for them to achieve those incremental gains in performance.

Periodization can be as simple, or as complex as you need it to be. That's the beauty of it.

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Physiological Basis Behind Periodization

What is periodization based on? How do we determine what variables to manipulate and how to manipulate them to our advantage in terms of training adaptations?

The answer comes from the understanding human physiology and how we respond to stress. Here are 3 of the overarching principles and paradigms that make exercise and sports planning possible: General adaptation syndrome (GAS), Stimulus-Fatigue-Recovery-Adaptation (SFRA) and Fitness-Fatigue Model (F-F)

General Adaptation Syndrome (GAS)

The General Adaptation Syndrome (GAS) is a model of stress created by Hans Selye to describe and stereotype the physiological responses of the nervous and endocrine system to a stressor. GAS is categorized into 3 stages: alarm stage, resistance stage and the exhaustion stage. During the alarm stage, the body reacts to the stressor by releasing hormones in order to restore homeostasis. The resistance stage, which can also be referred to the adaptation stage, is where physiological defenses are strengthened in anticipation to future stressors. The exhauastion stage is reached when the stressor still persists and the body does not have sufficient resources to defend or repair itself.

Han Selye's General Adaptation Syndrome (GAS) illustrated.

The GAS syndrome as shown by a mouse reaction to a cat.

In relation to exercise and sports training, a disruption in homeostasis (in the form of training stress) manifests itself in the form of muscle soreness, fatigue, and a temporary decrease in performance. If the stress is maintained without proper recovery, overtraining can occur. However, if an athlete recovers adequately after a period of stress, or if the stressor is temporarily withdrawn, performance can rebound and increase beyond training levels; this is often coined the term supercompensation and is another driving principle behind periodization.

Stimulus-Fatigue-Recovery-Adaptation (SFRA)

GAS was originally created to describe a response to a general stressor, however has been critisized that it was not created specifically sports training. This resulted in a more refined concept, the SFRA model, to explain training stress and adaptations.

Taken from BretContreras.com. Example of the SFRA (or SRA) curve in the context of muscle hypertrophy. 

Although similar to the GAS model, the SFRA model concept states that training stress is dependent on many factors such as intensity and volume of training. The greater the intensity or volume of the training, the greater the stressor is, resulting in a higher amount of fatigue AND adaptation. Contrastingly, if the intensity or volume of training is insufficient, fatigue will not accumulate but training adaptations will not be made! As an athlete, you must introduce yourself to a progressively larger and larger training stimulus, not too small where you won't see any benefits from it, or not too large that you're unable to recovery from it.

In layman's terms: every time you perform a training session (stimulus), you start to build up fatigue in the form of muscle soreness and lowered energy levels. As you consume enough food and get enough sleep (recovery), you are able to recover from your workout and come back fitter and stronger than before (adaptation). In the strength training realm, these concepts are commonly described as "progressive overloads" where you're looking to increase the total amount weight lifted or total number of reps lifted every workout or every week, and "rest days" where you back off on the training stress in order to give your body time to recover. 

Fitness-Fatigue Model

The fitness-fatigue (F-F) model suggests that fitness and fatigue are inversely related, where strategies that maximize fitness and decrease fatigue will be the most optimal to improving sport performance. It is thought that when we introduce a training stressor, fitness adaptations and the accumulation of fatigue occur simultaneously. It is not until the stressor is withdrawn, where fatigue dissipates and fitness is increased. Unlike the previous 2 paradigms, the F-F model is able to differentiate between specific training stressors. An exercise that stresses the neuromuscular system (heavy deadlifts) may not neccessarily affect the aerobic energy system to the same degree as a 10km run would. A well-known example of the F-F model is the strategy of tapering; where training volume is dialed back in order to eliminate muscular fatigue and express maximal strength, power and endurance.

Note that all 3 of these paradigms are used simultaneously in modern day training periodization. Thanks to the access to technology we have today, the ability to monitor training variables and training stress has made these concepts more important and more effective. Even with that said, there are still people who believe periodization does not work any better than non-periodized programs or is a waste of time or practical to implement. Their beliefs holds some truths, however are still misguided at the end of the day. I will go into detail in later parts of this series. 

For now, soak in the information and take a look at how your current training fits the concepts discussed. Thanks for reading!

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

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