Understanding Player Load: Meanings and Limitations.

We present a critical reflection on the mechanical variable Player Load, which is based on acceleration data and commonly used in sports. Our motivation to write this paper came from the difficulties that we encountered in the calculation and interpretation of Player Load using our own data, since we did not use the Catapult Sports equipment, which is a merchandise of the company that proposed this variable. We reviewed existing literature in order to understand Player Load better; we found many inconsistencies in PL calculation methods and in the meanings attached to it. Accordingly, this paper presents a brief discussion on the meanings that have been assigned to Player Load, its limitations, and the lack of clear and complete information about Player Load calculation methods. Moreover, the use of arbitrary units and different practical meanings in the literature has associated Player Load with many physical quantities, thereby resulting in difficulties in determining what Player Load measures within the context of sports. It seems that Player Load is related to the magnitude of changes in acceleration, but not the magnitude of acceleration itself. Therefore, coaches and sports scientists should take this information into account when they use Player Load to prescribe and monitor external loads. We concluded that a deeper discussion of Player Load as a descriptor of external load is warranted in the sports sciences literature.