This study was done to clarify the qualitative and quantitative factors that influence the performance of national top long jumpers and to investigate the relationship of both factors by the case study method. The results obtained were as follows:
1. Introspective analysis (qualitative research) showed that athletes judge the success or failure of their performances from viewpoints such as the flow of the run-up, motion perception at takeoff, and so on, similarly to the results of research on motion consciousness.
2. When the succeessful and failed attempts are compared using biomechanical analysis (a quantitative approach), differences are evident in the angle of the upper trunk in the run-up phase, the angular velocity of the hip and knee joint extension in the takeoff phase, and the angular velocity of the thigh in the swing leg.
3. The success-failure judgments of attempts from the athletes' motion perception are made in almost the same motion phases as the judgments derived from biomechanical analysis. However, when the successful attempts and the failed ones are compared from both qualitative and quantitative viewpoints, the success-failure differences differ significantly from each viewpoint, and the differences are not always evident in the common motion phases.
