Approximate Entropy (Ap entropy) was developed as a method to quantify regularity of time-series data. The aim of this study was to examine problems in the application of Ap entropy to human movement data and to distinguish movement patterns by quantifying the regularity of experimental human movement data. The following results were obtained:

1) For a relatively periodic time-series function with a small number of periods, difference in both the number of data points and number of periods affected the Ap entropy value. Thus, for the application of Ap entropy, the number of data points and the number of periods should be made the same.

2) Under the experimental conditions of this study, the change in the Ap entropy value was in accordance with subjective judgment of movement patterns. This indicates that Ap entropy is an effective parameter for quantitatively distinguishing movement patterns in data that differ in time-series regularity.

The purpose of this study is to evaluate the lower limbs motion from the viewpoint of moment of inertia during running. The moments of inertia of three segments, the thigh, leg and foot of two runners were calculated in recover phase during running. Both of the two runners were world record holder of middle-distance, the one has high forward swing form and the another has low forward swing form. The change of the moments of inertia and their influence on angular accelearation, moment and power for the two runners' hip joint were discussed. The performances of the two runners were videotaped with a video camera operating at 60 Hz with exposure time of 1/500 or 1/1,000 s. Two-dimensional coordinates for determining the moment of inertia were computed by using Direct Linear Transformation Method from video data. The value of moment of inertia about their rotation axis thought the great trochanteric head for three segments of the right lower limbs was investigated. In recover phase, the low swing runner had greater rotational inertia than the high swing runner in three segments of the lower limbs, especially the peek value of the total of the three segments was 23% greater just before the leg landing. Affected by the moment of inertia, the low swing runner had a greater moment and power of the hip joint, but had a smaller rotational energy and translational energy in average and peek value. The preceding result explains that for high swing, because the moment of inertia and moment were small, the leg can be brought forward more quickly, for low swing the energy costed to bring the leg was smaller. In calculation of kinetic data the body segment parameter is necessary, so the result of moment, power and energy of the lower limbs will be influenced easily by the mass and moment of inertia of the leg and foot. That is, to choose a swing from of lower limbers for a runner, the running speed, running distance as well as the body propotion will became the impotent factors in recover phase.