This study was performed in 33 ski jumpers taking part in the All Japan Ski Competion to analyze their "Satz" motions during the contest with a three-dimentional computer motion analyzing system (APAS). These jumpers were divided into three groups: the Junior, Special, and Nordic combined jump groups. The take-off motion was measured in terms of angular velocities of three joints of the lower extremity and approach speed at "Kante". The peak angular velocity of the knee joint was synchronized with that of the hip joint only in the Special and Nordic combined jump groups. Slight ankle dorsi-flexion was included in the "Satz" motion. The peaks of angular velocities in the hip and knee joints were higher in the Special jump group than in the Nordic combined jump group. In the Junior jump group, the hip and knee joints depicted various curves, In the motion of "Satz", 1) the peak angular velocity of the hip joint was synchronized with that of the knee joint, 2) statistically, the greater the angular velocities of the hip and knee joints, the longer the jump, 3) the jumpers used joints of the ankle not to kick the "Kante", but push it, 4) there was not any statistically significant difference in angular velocity of the joint among the three jump groups, and 5) statistically the greater the approach speeds, the longer the jump. In order for the motion of "Satz" to overcome vertical drag and air resistance, the power of the muscles of the back, low back, buttocks, and lower extremities are also essential.
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