Nedeljkovic, A, Mirkov, DM, Markovic, S, and Jaric, S. Tests of muscle power output assess rapid movement performance when normalized for body size. J Strength Cond Res 23(5): 1593-1605, 2009-Among other routinely tested physical abilities, the tests of rapid movement performance and the tests of direct assessment of muscle power have been independently evaluated in complex batteries of physical fitness tests. Based on the scaling effects, we hypothesized that the tests of rapid movement performance assess the same physical ability as the tests of direct assessment of muscle power properly normalized for the effect of body size. Young physically active men (n = 111) were evaluated on 23 physical ability tests based on the assessment of muscle strength, muscle power, and rapid movement performance. When non-normalized data were used, a principle component analysis revealed a structure with overlapping tests from the above-mentioned groups including the indices of body size. However, when the indices of muscle strength and directly assessed muscle power were properly normalized for the effect of body size, the obtained structure was in line with the hypothesis. Most of the tests of both the direct assessment of muscle power and rapid movement performance proved to belong to the same factor, whereas the muscle strength tests and body size measures, respectively, loaded the remaining 2 factors. This result suggests that the rapid movement performance could be employed to assess muscle power and, possibly, the neuromuscular efficiency in general, which could be important for understanding some basic aspects of the design and function of the human locomotor system. An important practical implication of our findings could be that the direct assessment of muscle power (that usually requires expensive equipment and complex data processing procedures) could be skipped from the complex batteries of physical fitness tests and replaced by generally simpler tests of rapid movement performance.