Have you ever noticed athletes or fitness clients making initial gains on a new program only to reach a plateau after a few weeks?

Most coaches I have ever worked with answer yes to the above question. This means they have experienced the Principle of Accommodation.

The Principle of Accommodation, often considered a general law in biology, states that the response of a biological object to a constant stimulus decreases over time. 

In the case of strength and conditioning or fitness training, the “biological object” is the human mind-body and the stimulus is the training load.

The “training load” is not a well-defined term. The word “load” may be understood as the total external force applied TO or BY the human body. The load also has a qualitative component, in which structures and systems in the body experience or create the external force. A training load is created through the use of exercises performed with certain intensities, volumes, rest periods, and frequencies.

The Principle of Accommodation dictates that as a certain training load is repeated over time, the performance gain decreases and the body’s response to the training program diminishes.

It is the Principle of Accommodation that is the physiology behind the saying “the best program is the program that you are not using right now.” It points to the fact that any program gets gradually more ineffective (the performance gains drop) every time it is used.

What do you do when the athlete’s response to the training program diminishes as he or she reaches a plateau?

You probably have heard: “The definition of insanity is doing the same thing over and over and expecting different results.” When the athlete/client has adapted to a program and performance gains are low or non-existent, it is necessary to change one or more program variables in order to stimulate new progress.

When you make changes to the program, the result is a new period with new content, structure, and maybe even a new target training objective.

The definition of periodization is a division into periods with different target training adaptations, structures, and content. Therefore, whenever you create a new period in the training program, you are applying periodization.

As a practical example, take a look at the first week and the final week of one training cycle inside The Barbell WOD. While the difference isn’t drastic, you’ll notice that Dave Spitz has changed the loading just enough to illicit adaptation within a training cycle.

Barbell WOD Plus – Clean & Mean – Week 1

Barbell WOD Plus – Clean & Mean – Week 4

Have you ever experienced a situation where an athlete has great energy in some weeks and then a few weeks later becomes exhausted and maybe even acquires an overuse injury?

Canadian biologist Hans Selye coined the term General Adaptation Syndrome (GAS) to describe how the adrenal glands respond to an initial alarm reaction followed by a reduction of an organism’s function in reaction to a noxious stimulus. The key to continually adaptating to the stress is the timely removal of the stimulus so that the organism’s function can recover. 

Eastern European scientists and physicians found similarities between the pattern of the training response in athletes and the stress patterns observed by Selye. According to the General Adaptation Syndrome, there is a three-stage response to the stress: 

Stage 1: Alarm Phase

When a new and more intense stress or stimulus (type, volume, and intensity) is applied, the first response is the shock or alarm phase that may be characterized by excessive soreness, stiffness, and a drop in performance. This phase may last days or weeks.

In some cases, the alarm phase is associated with depletion of biochemical substances like glycogen. However, certain texts assert it has never been proven which substances need to be looked at to understand this process. These texts also deem the GAS as too simple to explain progress. 

Stage 2: The Resistance Phase

At any instant the body has a definite ability to respond and adapt to the training stimulus, termed the Current Adaptation Reserves (CAR). The body adapts to the stimulus through various neurological, biochemical, structural, and mechanical adjustments leading to increased performance. Examples of such adjustments include increased cardiac output and enzyme concentrations (adaptations to aerobic training) and increased neural drive/neural activation (adaptations to resistance training). 

The resistance phase can be referred to as supercompensation and is associated with enhanced levels of biochemical substances.

Example: one theory of muscle hypertrophy is called the Energetic Theory of Muscle Hypertrophy. According to this theory, muscle catabolism (breakdown) is stimulated by a lack of energy for protein synthesis during resistance training sessions.

This means DURING sessions, muscle protein can actually DECREASE. Then, during the recovery phase, also known as the resistance or supercompensation phase, the balance is reversed and protein synthesis exceeds protein breakdown. The results are a net increase in muscle. 

Source: The Paradox of the Strength & Conditioning Professional (8 Weeks Out)

Stage 3: The Exhaustion Phase

If the stress persists for an extended period of time, the body loses the ability to adapt to the stress and soreness, stiffness, staleness, and maladaptation may occur as a consequence of overwork/overstress. 

Based on the General Adaptation Syndrome, the training stimulus must be strong enough and new enough to stimulate the alarm phase. The training stimulus must be applied repeatedly as long as the athlete/client is in the resistance phase. Lastly, the training stimulus must be removed at the beginning of, or early into, the exhaustion phase.

The General Adaptation Syndrome can be understood on two different levels. The first level is the neurological, biochemical, structural, and mechanical changes that underlie a second level consisting of easily observable performance changes. So while the General Adaption Syndrome may have its shortcomings in completely explaining the body’s response to the training stimulus, it is still a useful model for understanding training progress.

In relation to periodization, the General Adaptation Syndrome supports the strategy of alternating periods with an increased, developmental, stressing training stimulus (training load) with periods of a reduced training stimulus that allow the body to recover and supercompensate.

Research has been conducted on linear, reverse linear, daily undulating, and block periodization. And some researchers conclude that “comparative studies of non-varied programs and periodized programs in which serial testing was performed demonstrate that non-varied programs can result in training plateaus, whereas, periodized programs result in more consistent fitness gains.” 

Other researchers believe, despite the large number of controlled studies on periodization, the scientific evidence for periodization is lacking and the studies that are conducted mainly serve to prove that variation is important. 

As coaches, our conclusion must be that the scientists are not in agreement on the scientific evidence for periodization. This disagreement is one reason that scientific study has been placed as argument #3 and not #1 in this article.

However, I truly believe there is a very high amount of scientific evidence to support components of a periodized training program.

When we consider how specific types of training inter-relate, we realize there are three major types of relationships that can be described:

1. An ideal sequence of physical quality development 

Example: The development of strength, speed, power, and endurance may take place more safely and effectively in the presence of adequate levels of flexibility that allow the athlete-client to perform the movements with optimal form.

Effect on periodization: A period when the development of component A (flexibility) precedes a period with the development of component B (strength, speed, power or endurance)

2. The possibility of synergy between the training of two bio-physical qualities.

Example: The exploitation of post-tetanic potentiation by combining strength and power exercises in the same sessions.

Effect on periodization: If power is a part of the athlete’s goal, there can be a period where component A (strength) and component B (power) are trained together

3. The risk of incompatibility between two physical qualities.

Example: Intense anaerobic workloads can suppress aerobic enzymes and the oxidative process and lead to conflicting response in the adaptation process.

Effect on periodization: If aerobic and anaerobic performance is the goal, there must be a period with a focus on aerobic training and another period with anaerobic training.