Key transition technology of ski jumping based on inertial motion unit, kinematics and dynamics

Abstract

Background The development and innovation of biomechanical measurement methods provide a solution to the problems in ski jumping research. At present, research on ski jumping mostly focuses on the local technical characteristics of different phases, but studies on the technology transition process are less. Objectives This study aims to evaluate a measurement system (i.e. the merging of 2D video recording, inertial measurement unit and wireless pressure insole) that can capture a wide range of sport performance and focus on the key transition technical characteristics. Methods The application validity of the Xsens motion capture system in ski jumping was verified under field conditions by comparing the lower limb joint angles of eight professional ski jumpers during the takeoff phase collected by different motion capture systems (Xsens and Simi high-speed camera). Subsequently, the key transition technical characteristics of eight ski jumpers were captured on the basis of the aforementioned measurement system. Results Validation results indicated that the joint angle point-by-point curve during the takeoff phase was highly correlated and had excellent agreement (0.966 ≤ r ≤ 0.998, P < 0.001). Joint root-mean-square error (RMSE) differences between model calculations were 5.967° for hip, 6.856° for knee and 4.009° for ankle. Conclusions Compared with 2D video recording, the Xsens system shows excellent agreement to ski jumping. Furthermore, the established measurement system can effectively capture the key transition technical characteristics of athletes, particularly in the dynamic changes of straight turn into arc in inrun, the adjustment of body posture and ski movement during early flight and landing preparation.

Computational Fluid Dynamics Simulation Study on Aerodynamic Characteristics under Unfavorable Conditions during Flight Phase in Ski Jumping

“…After the take-off phase, it is crucial for the athlete to assume a stable flying position as soon as possible early during the flight phase [2], minimize drag [3], and achieve a complete balance between backward and forward angular momentum rotations [4]. The flight phase is where the aerodynamic characteristics of ski jumping are most evident, and researchers have conducted studies on the aerodynamic characteristics during this phase using wind tunnel experiments, combined field measurements and numerical simulations, among other methods [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Computational fluid dynamics (CFD) is the preferred tool for visualizing and analyzing the flow field around the athlete, enabling the analysis of aerodynamic forces, pressure distribution, and detailed flow information during motion.…”