Slopes are often used in sprint training, but there has been little previous study of the effects of slope inclination on sprinting motion. This study therefore investigates this topic with the aim of improving the utilization of slopes in sprint training. Participants were 9 male collegiate sprinters, who performed 40 m sprints on three kinds of slopes (1.3％, 7.4％, and 13.1％) and on a flat course. At 30 m from the starting line, three high-speed video cameras recorded each participant’s motion for analysis. Analysis indicated that steeper slopes increasingly decreased sprint speed and stride length. On the 1.3％ and 7.4％ slope, the angle of the knee joint before grounding of the foot and the angle of the foot angle when grounding of the foot was smaller than on a flat course. On the 13.1％ slope, grounding of the foot was performed as the foot was pulled toward the body, and the angle of the knee joint when grounding of the foot was smaller than on a flat course. And steeper slopes increasingly, increased knee joint extension during the support phase and the time of latter support phase. In sprint training on the 1.3％ slope, sprinters could sprint at speeds similar to those on the flat course, but it needs to consider that the degree of ankle extension during the support phase increased. Sprint training on the 7.4％ and 13.1％ slopes was useful to strengthen the extension power of knee joint, but a necessary consideration was that sprint running motion during the support phase differed from that of high speed sprinting.
