| The kinematical data of Double-Push is obtained by means of image measurement from the skaters, as the representative research object of this technique, in experiment, who took part for times in the national in-line speed skating competitions. The purpose is to establish a correct concept of double-push by analyzing and describing its kinematical features and showing the structural rules, reveal its interior high efficiency, and in a way contribute to the scientific training methods and the widespread of this sport. The double-push research is conducted mainly in three aspects: analysis of the movement phases, changes in movement of the skater's gravity center and description of body position in motion. The first aspect includes movement phases divisions, time features of each movement phase, distance analysis of each movement phase in motion, and the discussion on the connection among step length, step frequency and pace, etc. The second contains the analysis of gravity center's changes on X,Y,Z axis and the change velocity of gravity center. The last one includes the pushing leg's joint angles and their angle velocity, the free leg's joint angles and their angle velocity, and analysis of angle velocity of the upper body joints.Conclusion:1 Each single step of the double-push can be divided into 4 movement phases;With the rising speed, the duration of the two-foot-support reduces;The relation between step frequency, step length and step velocity: step frequency is the dominating factor that affects the double-push;Velocity affects the range of the gravity center's displacement, which is relatively large.2 The joint angles of the free leg are becoming larger during the support of the right medial skate.3 The blade change of the supporting leg arises before the back-sway of the free leg reaches to its maximum. The ankle applies force strikingly during the absence of the free leg from the ground.4 The coordination of the upper limb-sways plays an essential role in the double-push.
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