Over time, approaches to training and performance have shifted alongside changes in what we believe to be best practice. Concepts that were once widely accepted are refined, challenged, or replaced as our understanding improves. This process is not a failure of science, but a reflection of its strength: a willingness to continually re-evaluate assumptions in pursuit of better explanations and better outcomes.

Across these changes, some relative constants have remained. While methods and terminology evolve, our understanding of many the most basic underlying physiological processes governing human biology have proven relatively stable. These concepts, often referred to as “first principles” represent our most fundamental understanding of biology. The purpose of this article is to discuss how we apply this knowledge to guide our training philosophy.

At its core, the idea is fairly straightforward. All biological life is organized in a hierarchical arrangement of functional units of increasing size and complexity. Atoms and molecules combine to form cells, cells combine to form tissues, tissues form organs, and organs together form an organism.

At the level of the whole organism, humans display remarkable biological and psychosocial diversity. However, the cellular and tissue-level operations supporting these traits are fairly consistent across individuals. It is directly upon these foundational processes that our training programs are built.

Our methods are rooted in fundamental sciences such as anatomy, physiology, kinesiology, and neurology. These disciplines represent generations of scientific study aimed at understanding how the human body is structured, how it functions, and how it responds to stresses. As a result, while fitness trends and training styles may change over time, our understanding of these fundamental biological processes, remains relatively stable.

Barring variations due to genetics or certain medical conditions, discussion of which is beyond our scope, human cells and tissues tend to respond to stimuli in fairly predictable ways [1-2]. Training, in its simplest form, involves the systematic application of stimuli to encourage adaptation in a desired direction. Improvements in strength, mobility, cardiovascular capacity, and body composition all depend on applying the right stimulus at the right time to drive specific physiological changes [2].

The knowledge we base our system off of originates from two primary sources of evidence. The first consists of foundational biological principles that have been examined and re-examined over long periods of time and are broadly accepted within the scientific community, such as those commonly presented in academic textbooks. The second includes peer-reviewed research examining outcomes across large population groups, often in the form of systematic reviews or meta-analyses. We combine both types of knowledge to inform our overall approach.

A “science-driven” approach does not imply rigid uniformity. Instead, it recognizes that while the processes of biological adaptation are consistent, their application must be aligned with an individual’s circumstances. Our training framework uses foundational scientific knowledge to design systems of stimulus application that respect both biological principles and real-world variability.

Importantly, we do not claim novelty in these ideas. Much of this knowledge has been well established for decades, and in some cases centuries. However, we find that training programs sometimes overlook these principles in pursuit of methods that may be misaligned with how the body actually adapts. However well intentioned, this disconnect often invites poor adherence and suboptimal outcomes for trainees and trainers alike.

Our goal is not to reinvent well-established scientific concepts. It is to present them in a clear, accessible format and to provide a practical framework for applying them to physical performance. Through this approach, we aim to facilitate users’ ownership over their training and provide tools by which to individualize it responsibly.

We explore a wide range of training-related topics through this lens in our expanding educational library. Combined with our training programs, this content is designed to provide a coherent and actionable knowledge base that supports thoughtful, progressive adaptation of the body’s systems over time.
References:

1. Roth RR. General adaptation syndrome (GAS). Research Starters: Health and Medicine. EBSCO; 2025. Accessed April 10, 2026. https://www.ebsco.com/research-starters/health-and-medicine/general-adaptation-syndrome-gas.
2. Frost HM. A 2003 update of bone physiology and Wolff’s law for clinicians. Angle Orthod. 2004;74(1):3–15.
3. Mueller MJ, Maluf KS. Tissue adaptation to physical stress: a proposed “physical stress theory” to guide physical therapist practice, education, and research. Phys Ther. 2002;82(4):383-403.

The Applied Physiologics Team
Lead Author: Michael Wahlig PT, DPT, OCS, COMT, CSCS
Published: 4/22/2026

This content is intended for educational purposes only and does not constitute medical, physical therapy, or individualized exercise advice.