The word 使劲 is formed by conceptually fusing two independent ideas: 使 (to use, employ) and 劲 (strength, force). It is not merely their sum, but a seamless compound where the first character acts upon the second, creating the single, integrated notion of "applying one's strength" or "exerting effort". The formation captures the momentary action of channeling physical or mental energy into a task, with the characters' original meanings blending into a unified, verb-oriented concept.