Uploaded May 2026 | Updated September 2026, 1 week ago
Coach explains a measurable, scientific definition of fitness
Continuing his presentation at the National War College at National Defense University, Coach Glassman outlines a scientific framework for measuring fitness through human performance. He proposes defining fitness as increased work capacity across broad time and modal domains, using the basic physical units of meters, kilograms, and seconds. In this model, performance can be quantified through power—force multiplied by distance and divided by time—and tracked across a range of efforts, from short bursts to longer endurance work. By graphing power output across these durations, an individual’s total work capacity can be measured in objective, repeatable terms.
Greg criticizes much of the fitness industry for relying on vague claims and physiological markers that are disconnected from real-world performance. Instead, he argues that any training program must be evaluated through measurable outcomes. He proposes three key criteria for assessing training methods: efficacy, efficiency, and safety—what results a program produces, how quickly those results occur, and how many participants are injured in the process. For soldiers preparing for the unpredictable demands of combat, fitness must be developed across many different movements and time domains, and that any program claiming to deliver results should be able to defend those claims with clear, measurable data.
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The Glassman Archive is a comprehensive repository of Greg Glassman’s work during his leadership of CrossFit.
This collection preserves his original material and the foundational ideas he shared. We believe these insights are worth promoting and protecting. These lessons continue to inform his ongoing work with the Broken Science Initiative and MetFix.
Coach explains a measurable, scientific definition of fitness
Continuing his presentation at the National War College at National Defense University, Coach Glassman outlines a scientific framework for measuring fitness through human performance. He proposes defining fitness as increased work capacity across broad time and modal domains, using the basic physical units of meters, kilograms, and seconds. In this model, performance can be quantified through power—force multiplied by distance and divided by time—and tracked across a range of efforts, from short bursts to longer endurance work. By graphing power output across these durations, an individual’s total work capacity can be measured in objective, repeatable terms.
Greg criticizes much of the fitness industry for relying on vague claims and physiological markers that are disconnected from real-world performance. Instead, he argues that any training program must be evaluated through measurable outcomes. He proposes three key criteria for assessing training methods: efficacy, efficiency, and safety—what results a program produces, how quickly those results occur, and how many participants are injured in the process. For soldiers preparing for the unpredictable demands of combat, fitness must be developed across many different movements and time domains, and that any program claiming to deliver results should be able to defend those claims with clear, measurable data.
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The Glassman Archive is a comprehensive repository of Greg Glassman’s work during his leadership of CrossFit.
This collection preserves his original material and the foundational ideas he shared. We believe these insights are worth promoting and protecting. These lessons continue to inform his ongoing work with the Broken Science Initiative and MetFix.
