Kinematic Analysis of Butterfly Swimming

This study aimed to examine the relative phase of the arm and leg movements and the percentage of each of the 4 arm movement phases at three race paces of the butterfly swimming between two levels of swimmers based on the temporal analysis. Eight elite male swimmers and eight club level college male swimmers participated in the study. Two underwater high-speed cameras (200Hz) were set in the transverse and sagittal plane under the water and synchronized to capture one cycle of butterfly stroke movement. The kinematics data were digitized and calculated with the Kwon 3D software. The continuous relative phase was calculated using the normalized time series of the angular displacement and angular velocity of the shoulder and knee joints angles. Macroscopically, one cycle of the arm-leg coordination pattern can be observed between two levels at three race paces in butterfly stroke: a consistent relationship (2:1) exists between two dolphin kicks and one arm stroke in butterfly swimming. The continuous relative phase analyses showed that, in the beginning of the stroke-catch phase, the continuous relative phase was from anti-phase (-180°) to in-phase (50°). For the pull phase, the in-phase relation (±50°) remained unchanged throughout the stage. During the push phase, the relative phase gradually increased toward anti-phase (180°). The percentage of catch, pull, push, and recovery phases were not evenly distributed across one cycle of the butterfly stroke. Especially in elite group, there is a trend of decreasing the percentage of catch phase. In conclusion, these results provide useful information for swimmers as well as coaches to examine the swimming movement of the butterfly stroke.