This study was intended to clarify the relationship between features of change velocity and performance of elite athletes in men's 400-m hurdles (400 mH). Races of 400 mH were videotaped with several video cameras panning from start to goal at 60 fields/s. After a time indication was superimposed on each field of the VTR images, the time at touchdown immediately after hurdling was recorded. Using the flash of the starter's gun recorded on the VTR image, each hurdle touchdown time from the start and each section (hurdle to hurdle) time was obtained. Each section was defined as follows: S1 was from the start to 2^nd hurdle; S2 was from the 2^nd to 5^th hurdle, S3 was the 5^th to 8^th hurdle, and S4 was from the 8^th hurdle to finish. Results of the regression analysis showed significant correlations between the 400 mH race time and the total number of steps from hurdle to hurdle (TNS; r=0.397, p<0.05), S2 time (0.673, p<0.001), and S3 time (r=0.865, p<0.001), and the rate of deceleration from S1 to S2 (r=0.367, p<0.05), and from S2 to S3 (r=0.421, p<0.01), and the rate of S3 time in the race time (r=0.463, p<0.01). These results indicate that it is important to decrease TNS and to prevent decreasing velocity in S2 and S3, to attain a high performance.

Most of motions used in physical education and sports require generation of a great amount of mechanical energy and its effective use to achieve good performance. The purpose of this study was to investigate effects of technical training on the takeoff motion and mechanical energy-related parameters in the standing long jump. Twenty-one male adults were participated in the technical training session for two days, which was designed to improve the jumping technique and jumping distance of the standing long jump. Jumping motion of the subjects was videotaped with a high-speed video camera and ground reaction forces were measured with a force platform in pre and post training sessions. A two-dimensional motion analysis technique was used to calculate total mechanical work (Wtotal), effectiveness index of mechanical energy utilization (EI), joint force power (JFP) and segment torque power (STP).

After the technical training, the subjects increased the forward lean of the body at the instant of the takeoff. This change resulted in the more forward extended takeoff position and the increase in the horizontal takeoff velocity as well as the jumping distance. There were two types of change in mechanical energy-related parameters by the technical training. One was an EI+ type which increased EI but decreased Wtotal, and another was a Wtotal+ type which increased Wtotal but decreased EI. The EI+ type decreased the mechanical energy flow, especially to the trunk from the legs and the trunk backward rotation, while the Wtotal+ type increased both. These results indicated that the two-day technical training of the standing long jump was able to improve not only the jumping distance but also the takeoff technique, and that the effects could be categorized by the mechanical energy flow to the trunk from the legs and the change in the trunk rotation during the takeoff phase.