Mechanical misconceptions: Have we lost the "mechanics" in "sports biomechanics"?

Biomechanics principally stems from two disciplines, mechanics and biology. However, both the application and language of the mechanical constructs are not always adhered to when applied to biological systems, which can lead to errors and misunderstandings within the scientific literature. Here we address three topics that seem to be common points of confusion and misconception, with a specific focus on sports biomechanics applications: (1) joint reaction forces as they pertain to loads actually experienced by biological joints; (2) the partitioning of scalar quantities into directional components; and (3) weight and gravity alteration. For each topic, we discuss how mechanical concepts have been commonly misapplied in peer-reviewed publications, the consequences of those misapplications, and how biomechanics, exercise science, and other related disciplines can collectively benefit by more carefully adhering to and applying concepts of classical mechanics.