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

(2023) 22:21 Yu et al. BioMedical Engineering OnLine https://doi.org/10.1186/s12938-023-01087-x RESEARCH BioMedical Engineering OnLine Open Access Key transition technology of ski jumping based on inertial motion unit, kinematics and dynamics Jinglun Yu1,2, Xinying Ma3, Shuo Qi2, Zhiqiang Liang1,2, Zhen Wei2, Qi Li1,2, Weiguang Ni4, Shutao Wei5 and Shengnian Zhang1,2* *Correspondence: 1 Key Laboratory of Exercise and Health Sciences of Ministry of Education, Shanghai University of Sport, Shanghai 200438, China 2 School of Exercise and Health, Shanghai University of Sport, Shanghai, China 3 Foundation Courses Research Center, Silicon Lake College, Kunshan, China 4 Physical Education College, Jilin University, Changchun, China 5 361 Degree Co., Ltd., Xiamen, China 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. Keywords: Ski jumping, Technology, Kinematics, Dynamics, IMU, Measurement systems © The Author(s) 2023. 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The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publi cdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Yu et al. BioMedical Engineering OnLine (2023) 22:21 Background Ski jumping has a long history of development, and it has elicited increasing attention from researchers in recent years [1]. Ski jumping performance is frequently divided into four different phases: inrun, takeoff, flight (early and stable flight) and landing [2]. The wide range and long distance of motion scenes in sports make formulating experimental plans difficult. The severe outdoor environment during winter also challenges the collection of high-quality data. On the one hand, measurement accuracy should be considered for the measurement methods; on the other hand, the adverse effects of the measurement system on the athletes should be reduced [3]. During the primary stage of the study, these contradictory goals cannot be achieved simultaneously, and some trade-offs must be made in executing processes. However, with the development of science and technology, such as the innovation of instruments and equipment, the application of wireless transmission technology and the novel idea of applying inertial measurement units (IMUs) to ski jumping research [4], problems in research and measurement can gradually be solved. The characteristics of ski jumping necessitate that the technical movements of athletes are largely executed on the sagittal plane, making 2D video recording [5, 6] the primary research method. In recent years, IMUs have been widely used; they exhibit the advantages of high precision, small size and strong portability, making them the best choice for sports training and performance feedback [7–9]. Similarly, the use of wireless pressure insoles can more conveniently and economically collect the dynamic parameters of takeoff and landing without affecting athletes’ performance of technical movements [10, 11]. In the research on the biomechanics of ski jumping, most studies have focused on local technical characteristics at different phases, particularly takeoff and flight. Meanwhile, research on the transition process between different technologies (e.g. the process of straight turn into arc in inrun, the formation of ‘V’-shaped technology in early flight and preparations before landing) is less, and attention is low. However, ski jumping technology is continuously developing. Athletes can only achieve the best flight distance when they accurately complete the corresponding technical requirements and transition in each link. Arndt [12] pointed out that the technical mistakes made by ski jumpers in the previous phase (particularly in takeoff ) cannot be remedied or eliminated through a flight phase technology. Therefore, building a whole or large measuring range for observing changes in athletes’ movement characteristics in continuous state and the transition process between different technologies seems necessary to deepen the understanding of athletes, coaches and researchers regarding ski jumping. The objective of the current study was twofold. Firstly, it aimed to evaluate a measurement system (i.e. the merging of 2D video recording, IMU and wireless pressure insole) that can capture a wide range of sport performance in an outdoor experiment. Secondly, on the basis of the aforementioned research methods whilst observing the overall movement stage, (...truncated)