The Effect of a Change in the Difficulty Level of the Big Air Jump Take-off Phase in Joint Kinematics of Snowboarding Athletes

Abstract

The purpose of this study was to elucidate the kinematic differences in the take-off phase of backside 360°, backside 540°, and backside 720° jumps in freestyle snowboarding. The study was conducted with 3D motion analysis. Five athletes (1 woman, 4 men), aged 18-30 years, performed backside 360°, backside 540°, and backside 720° jumps from Ruka Park’s biggest jumper. The jumps were filmed with two high-speed cameras, one on each side of the jumper. The performance area was calibrated with a 2 m x 4 m calibration frame. Videos were manually digitized with Vicon Motus 10.0.1. Segments were determined according to DeLeva’s (1996) segment parameters. Twenty markers in each subject were digitized from each frame and both cameras. Vicon Motus 10.0.1 was used to calculate centre of mass horizontal and vertical velocities, knee and hip joint angles, and knee and shoulder joint angular velocities for each jump. The results were interpreted descriptively and on a case. Results show that each subject had their own style of doing the jumps. Centre of mass vertical velocity increased as the difficulty level of the jump increased for all subjects. Instead, centre of mass horizontal velocity decreased as the difficulty level of the jump increased for some subjects, and for some subjects, centre of mass horizontal velocity increased as the difficulty level of the jump increased. The change in average knee joint angles in front leg as the difficulty level of the jump changed varied between subjects. Average knee joint angles in back leg increased as the difficulty level of the jump increased. Average hip joint angles increased both in front and back legs as the difficulty level of the jump increased for all but one subject. Knee and elbow joint angular velocities were higher when there were more rotations in the jump. As a conclusion, the joint angles in knees and hips, and the angular velocities in knee and elbow joints varied between jumps. However, the changes were subject-dependent. Centre of mass vertical velocity increased as the difficulty level of the jump increased, and centre of mass horizontal velocity varied more. Further studies should include more subjects to have statistical information from the differences. Also adding more cameras would make digitizing and analysing easier. In the future, the effects of the weather must also be better considered when planning measurements. Accelerometers, pressure insoles, and muscle activity measurement could possibly be combined with further studies.