Authors’ Reply to Buckner et al.: General Adaptation Syndrome as a Foundation for Periodization

This document serves as a formal reply by Aaron J. Cunanan, Brad H. DeWeese, John P. Wagle, Kevin M. Carroll, Robert Sausaman, W. Guy Hornsby III, G. Gregory Haff, N. Travis Triplett, Kyle C. Pierce, and Michael H. Stone to a letter submitted by Buckner et al. [ $1$ ].
The correspondence addresses the ongoing discussion regarding the article "The General Adaptation Syndrome: A Foundation for the Concept of Periodization" published in Sports Medicine [ $2$ ].
The authors aim to clarify the role of the General Adaptation Syndrome (GAS) as an appropriate mechanistic model for conceptualizing training periodization, countering claims made by Buckner et al. in their letter and previous reviews [ $3, 4$ ].
The reply was published online on $1$ March $2018$ by Springer International Publishing AG, part of Springer Nature $2018$ .

Buckner et al. [ $1$ ] suggest a restricted perspective where only Hans Selye’s original experimental papers should be considered when assessing the GAS, effectively dismissing Selye’s own reviews which do not present new raw data.
The authors fundamentally disagree with this position based on three points:
- (i) It implies that scientific conclusions cannot be expanded, amended, or revised without new data, despite advancements in general scientific knowledge.
- (ii) It suggests that literature reviews do not contribute to the body of scientific knowledge.
- (iii) It implies that Selye himself was unqualified to comment on his own GAS concept.
Reference to Selye’s summary of experiments [ $5$ ]: Tables $1, 2, \text{and } 3$ conceptually support fundamental modern periodization principles:
- Overload.
- Specificity.
- Variation.
- Reversibility.
Viru [ $6, 7$ ] provided additional clear summaries linking the GAS concept directly to training adaptations.
The authors argue that Buckner et al.’s restricted perspective "inexplicably omits substantive developments" and leads to an argument against isolated GAS components removed from their scientific and practical context.

A central point of contention is the definition of the GAS. Buckner et al. [ $1$ ] rely on Selye’s original experimental data on thymus weight and mortality.
The authors clarify that Selye utilized these data as surrogate measures (indices) of an animal’s resistance to a stressor and its functional state (adaptation/resistance).
Selye’s detailed cataloging of variable symptoms in response to specific stimuli [ $5, 8, 9$ ] demonstrates that GAS is not defined by any single set of physical symptoms (e.g., thymus involution).
Emphasis is placed on the functional effects of the GAS rather than the "rote documentation" of physical changes.
The authors view Buckner et al.’s suggestion—that the most effective periodized program should produce the least amount of thymus involution and adrenal hyperplasia—as a mischaracterization of Selye’s work and the GAS concept.

The authors address Buckner et al.’s critique of their citation of Selye regarding the periodicity of stress and recovery.
Selye’s review [ $10$ ] includes a section titled "The Physio-pathology of Periodicity," which highlights pathologies resulting from a lack of periodicity.
Verbatim quote from Selye: "stress-reactions… are well tolerated only during short periods and tend to cause severe complications if they act upon the body persistently over a long time."
Selye suggested a potential therapeutic benefit in the "application and withdrawal of stress."
Broad Application: Although Selye does not explicitly use the term "acute exercise," he mentions "muscular work." As GAS is a nonspecific model, it applies to various stressors, including exercise.
Practical Implications for Training:
- Explicit guidance on beneficial vs. pathological outcomes from stress.
- Necessity for planned variation (e.g., heavy and light training days) and scheduled rest.
Risks of Unvaried Training:
- Documented negative effects of sustained high training loads [ $11–14$ ].
- Interactions between training load, performance, subjective wellness, and injury/illness risk [ $15–25$ ].
- Observations of international coaches in weightlifting and track and field suggest that training systems with low variation in volume, intensity, or exercise selection have the highest incidences of performance-enhancing drug (PED) use, implying such methods exceed normal human physiological capabilities.

The authors criticize Buckner et al.’s dismissal of formal definitions for periodization and programming, which contributes to conceptual confusion.
Critique of Mattocks et al. [ $4$ ]: This review largely compares loading schemes (classified as programming) rather than the sequential development of fitness characteristics (classified as periodization).
The Principle of Specificity and Athletic Demands:
- Most sports require a vast repertoire of skills and tactics.
- These are underpinned by various forces, rates of force development, movement amplitudes, movement velocities, and bioenergetic flux.
- Simultaneously addressing every quality is unfeasible and likely detrimental to athlete performance.
Deterministic Planning: If an athlete allocates targeted development of specific fitness characteristics to different periods of time (periodization), the training content must vary between phases.
Sequencing and content of these phases significantly impact final training outcomes [ $26–28$ ].
Examples in Specific Sports: Even sports with fewer distinct fitness characteristics (e.g., weightlifting or powerlifting) require loading variation (avoiding constant lift of $1$ -repetition maximums) particularly during hypertrophy phases to move up a weight class.

The authors conclude that Buckner et al. based their opinions on an incomplete version of the GAS and disregarded formal definitions of periodization.
Functional changes in resistance and adaptation observed during the GAS are clearly visible in human response to training.
The Fitness-Fatigue Paradigm [ $29, 30$ ]: This is identified as a specifically useful model for understanding the functional perspective of the GAS in relation to training and athletic performance.
Scientific findings regarding the time courses of adaptations, appropriate stimuli for specific adaptations, and the influence of "conditioning factors" necessitate the careful planning of sports training.
The GAS and periodization provide the conceptual frameworks required to apply these scientific findings effectively.