Köhler Hans-Peter, Schödlbauer Maximilian, Witt Maren
Department of Biomechanics in Sports, Leipzig University, Leipzig, Germany.
Front Sports Act Living. 2024 Sep 27;6:1445455. doi: 10.3389/fspor.2024.1445455. eCollection 2024.
The throwing motion in the javelin throw applies high loads to the musculoskeletal system of the shoulder, both in the acceleration and deceleration phases. While the loads occurring during the acceleration phase and their relationship to kinematics and energy flow have been relatively well investigated, there is a lack of studies focusing the deceleration phase. Therefore, the aim of this study is to investigate how the throwing arm is brought to rest, which resultant joint torques are placed on the shoulder and how they are influenced by the kinematics of the acceleration phase.
The throwing movement of 10 javelin throwers were recorded using a 12-infrared camera system recording at 300 Hz and 16 markers placed on the body. Joint kinematics, kinetics and energy flow were calculated between the touchdown of the rear leg and the timepoint of maximum internal rotation after release +0.1 s. Elastic net regularization regression was used to predict the joint loads in the deceleration phase using the kinematics and energy flow of the acceleration phase.
The results show that a significant amount of energy is transferred back to the proximal segments, while a smaller amount of energy is absorbed. Furthermore, relationships between the kinematics and the energy flow in the acceleration phase and the loads placed on the shoulder joint in the deceleration phase, based on the elastic net regularized regression, could be established.
The results indicate that the loads of the deceleration phase placed on the shoulder can be influenced by the kinematics of the acceleration phase. For example, an additional upper body forward tilt can help to increase the braking distance of the arm and thus contribute to a reduced joint load. Furthermore, the energy flow of the acceleration phase can be linked to joint stress. However, as previously demonstrated the generation of mechanical energy at the shoulder seems to have a negative effect on shoulder loading while the transfer can help optimize the stress. The results therefore show initial potential for optimizing movement, to reduce strain and improve injury prevention in the deceleration phase.
标枪投掷动作在加速和减速阶段都会给肩部的肌肉骨骼系统施加高负荷。虽然加速阶段产生的负荷及其与运动学和能量流的关系已经得到了较为充分的研究，但针对减速阶段的研究却较为匮乏。因此，本研究的目的是探究投掷手臂是如何制动的，肩部会受到哪些合成关节扭矩，以及这些扭矩如何受到加速阶段运动学的影响。
使用一个12台红外摄像机系统，以300Hz的频率记录10名标枪运动员的投掷动作，并在身体上放置16个标记点。计算后脚着地至释放后最大内旋时间点+0.1秒之间的关节运动学、动力学和能量流。采用弹性网络正则化回归，利用加速阶段的运动学和能量流来预测减速阶段的关节负荷。
结果表明，大量能量被传回近端节段，同时吸收的能量较少。此外，基于弹性网络正则化回归，能够建立加速阶段的运动学和能量流与减速阶段施加在肩关节上的负荷之间的关系。
结果表明，减速阶段施加在肩部的负荷会受到加速阶段运动学的影响。例如，额外的上半身前倾有助于增加手臂的制动距离，从而有助于减轻关节负荷。此外，加速阶段的能量流与关节应力有关。然而，如先前所示，肩部机械能的产生似乎对肩部负荷有负面影响，而能量传递则有助于优化应力。因此，结果显示出在优化动作方面的初步潜力，以减少减速阶段的应变并改善损伤预防。
