Faculty of Sport, Technology and Health Sciences, St Mary's University, Twickenham, UK.
Ballet Healthcare, The Royal Ballet, Royal Opera House, London, UK.
Sci Rep. 2024 Sep 2;14(1):20371. doi: 10.1038/s41598-024-70194-z.
An abundance of degrees of freedom (DOF) exist when executing a countermovement jump (CMJ). This research aims to simplify the understanding of this complex system by comparing jump performance and independent functional DOF (fDOF) present in CMJs without (CMJ) and with (CMJ) an arm swing. Principal component analysis was used on 39 muscle forces and 15 3-dimensional joint contact forces obtained from kinematic and kinetic data, analyzed in FreeBody (a segment-based musculoskeletal model). Jump performance was greater in CMJ with the increased ground contact time resulting in higher external (p = 0.012), hip (p < 0.001) and ankle (p = 0.009) vertical impulses, and slower hip extension enhancing the proximal-to-distal joint extension strategy. This allowed the hip muscles to generate higher forces and greater time-normalized hip vertical impulse (p = 0.006). Three fDOF were found for the muscle forces and 3-dimensional joint contact forces during CMJ, while four fDOF were present for CMJ. This suggests that the underlying anatomy provides mechanical constraints during a CMJ, reducing the demand on the control system. The additional fDOF present in CMJ suggests that the arms are not mechanically coupled with the lower extremity, resulting in additional variation within individual motor strategies.
在进行反跳（CMJ）时，存在大量的自由度（DOF）。本研究旨在通过比较无臂摆动（CMJ）和有臂摆动（CMJ）的跳跃性能和独立功能自由度（fDOF），来简化对这个复杂系统的理解。使用主成分分析（PCA）对从运动学和动力学数据中获得的 39 个肌肉力和 15 个三维关节接触力进行了分析，这些数据是在 FreeBody（基于节段的肌肉骨骼模型）中进行分析的。CMJ 的跳跃性能更高，因为地面接触时间增加，导致外部（p = 0.012）、髋关节（p < 0.001）和踝关节（p = 0.009）的垂直冲量更高，髋关节的伸展速度更慢，增强了近端到远端关节的伸展策略。这使得髋关节肌肉能够产生更高的力和更大的时间归一化髋关节垂直冲量（p = 0.006）。在 CMJ 期间，发现肌肉力和三维关节接触力有三个 fDOF，而在 CMJ 中有四个 fDOF。这表明，潜在的解剖结构在 CMJ 期间提供了机械约束，从而降低了控制系统的需求。CMJ 中存在的额外 fDOF 表明手臂与下肢在机械上没有耦合，导致个体运动策略中的额外变化。
