Yes, you may have read the guidelines for exercise policy statements rendered by organizations like the American College of Sports Medicine, and you might have encountered a feeble expression labeled a definition in an exercise physiology textbook, but none of these has ever qualified as a formal definition that complies with consistent academic conventions in physics, chemistry, math, and related classical science. For a usable language, each word's meaning must be delimited. In fact, to define actually means to delimit meaning or to give meaning a bounds. We define a word more, not by stating what it represents, but more by restricting what it means. To de-fine is to say what a word does not mean.
Modern science is distinguished by two important traits.
The supreme example of exactness in language is found in mathematics. A mathematician defines a concept such as point in geometry in such a manner that leaves you no latitude for confusing it with some other entity. Point is defined by delimiting meaning, by strictly excluding all other possibilities. The Pythagoreans came to power 2500 years ago. They left a legacy of exacting mathematical language.