A Unified System of Fitness Design proposes a new fitness framework that encompasses all fitness indicators in a holistic and comprehensive manner, striving to provide a comprehensive and inclusive definition of physical fitness, one that considers all attributes contributing to overall well-being, crafting a flexible framework that can adapt to diverse contexts and purposes of physical fitness assessments. This new book is divided into two parts. Part 1 explores redefining and reconstructing the concepts of an inclusive and holistic fitness framework. In Part 2, the reader is encouraged to embark on a journey to discover the interconnected system functions of physiological health, homeostasis, motor control, and energy regulation. Part 3 reinforces the role of wellness in the Unified Systems Fitness Design, guided by the principles of inclusion and equity, in the decision-making process. Finally, the perpetual complementation theory emerged from the design, making sense of the cyclical connection between the system functions for health and skill and strengthening the Health-Ability-Task Suitability (HATS) Framework. There are still many uncharted territories in the realm of fitness and wellness. A Unified System of Fitness Design addresses these gaps in the literature and practice and seeks to inspire a transformative worldview that urges the reader to question the existing paradigms and explore innovative, inclusive approaches that cater to people with unique needs. In doing so, this exciting new volume aims to establish a common language for researchers and practitioners in the field, offering accurate and concise descriptions of each fitness component and its associated indicators in a universally understood terminology.