Mazzà Claudia, Iosa Marco, Pecoraro Fabrizio, Cappozzo Aurelio
Department of Human Movement and Sport Sciences, Università degli Studi di Roma "Foro Italico", Rome, Italy.
J Neuroeng Rehabil. 2008 Nov 17;5:30. doi: 10.1186/1743-0003-5-30.
The control of the head movements during walking allows for the stabilisation of the optic flow, for a more effective processing of the vestibular system signals, and for the consequent control of equilibrium.In young individuals, the oscillations of the upper body during level walking are characterised by an attenuation of the linear acceleration going from pelvis to head level. In elderly subjects the ability to implement this motor strategy is reduced. The aim of this paper is to go deeper into the mechanisms through which the head accelerations are controlled during level walking, in both young and elderly women specifically.
A stereophotogrammetric system was used to reconstruct the displacement of markers located at head, shoulder, and pelvis level while 16 young (age: 24 +/- 4 years) and 20 older (age: 72 +/- 4 years) female volunteers walked at comfortable and fast speed along a linear pathway. The harmonic coefficients of the displacements in the medio-lateral (ML), antero-posterior (AP), and vertical (V) directions were calculated via discrete Fourier transform, and relevant accelerations were computed by analytical double differentiation. The root mean square of the accelerations were used to define three coefficients for quantifying the attenuations of the accelerations from pelvis to head, from pelvis to shoulder, and from shoulder to head.
The coefficients of attenuation were shown to be independent from the walking speed, and hence suitable for group and subject comparison.The acceleration in the AP direction was attenuated by the two groups both from pelvis to shoulder and from shoulder to head. The reduction of the shoulder to head acceleration, however, was less effective in older women, suggesting that the ability to exploit the cervical hinge to attenuate the AP acceleration is challenged in this population. Young women managed to exploit a pelvis to shoulder attenuation strategy also in the ML direction, whereas in the elderly group the head acceleration was even larger than the pelvis acceleration.
The control of the head acceleration is fundamental when implementing a locomotor strategy and its loss could be one of the causes for walking instability in elderly women.
行走过程中头部运动的控制有助于稳定视觉流，更有效地处理前庭系统信号，并进而控制平衡。在年轻人中，平地上行走时上半身的摆动特点是从骨盆到头部水平的线性加速度减弱。在老年受试者中，实施这种运动策略的能力会下降。本文旨在更深入地探究在平地上行走时，年轻和老年女性控制头部加速度的机制。
使用立体摄影测量系统重建位于头部、肩部和骨盆水平的标记物的位移，16名年轻（年龄：24±4岁）和20名老年（年龄：72±4岁）女性志愿者以舒适和快速的速度沿直线路径行走。通过离散傅里叶变换计算在中-侧（ML）、前-后（AP）和垂直（V）方向上位移的谐波系数，并通过解析二次微分计算相关加速度。加速度的均方根用于定义三个系数，以量化从骨盆到头部、从骨盆到肩部以及从肩部到头部的加速度衰减。
衰减系数显示与行走速度无关，因此适合进行组间和个体比较。两组在从骨盆到肩部以及从肩部到头部的过程中，AP方向的加速度均有所衰减。然而，老年女性中肩部到头部加速度的减小效果较差，这表明在该人群中利用颈椎关节来衰减AP加速度的能力受到挑战。年轻女性在ML方向上也设法采用了从骨盆到肩部的衰减策略，而在老年组中，头部加速度甚至大于骨盆加速度。
在实施运动策略时，控制头部加速度至关重要，其丧失可能是老年女性行走不稳定的原因之一。
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