Aprigliano Federica, Martelli Dario, Tropea Peppino, Pasquini Guido, Micera Silvestro, Monaco Vito
The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy.
Department of Mechanical Engineering, Columbia University, New York, New York.
J Neurophysiol. 2017 Sep 1;118(3):1739-1748. doi: 10.1152/jn.00844.2016. Epub 2017 Jul 12.
This study was aimed at verifying whether aging modifies intralimb coordination strategy during corrective responses elicited by unexpected slip-like perturbations delivered during steady walking on a treadmill. To this end, 10 young and 10 elderly subjects were asked to manage unexpected slippages of different intensities. We analyzed the planar covariation law of the lower limb segments, using the principal component analysis, to verify whether elevation angles of older subjects covaried along a plan before and after the perturbation. Results showed that segments related to the perturbed limbs of both younger and older people do not covary after all perturbations. Conversely, the planar covariation law of the unperturbed limb was systematically held for younger and older subjects. These results occurred despite differences in spatio-temporal and kinematic parameters being observed among groups and perturbation intensities. Overall, our analysis revealed that aging does not affect intralimb coordination during corrective responses induced by slip-like perturbation, suggesting that both younger and older subjects adopt this control strategy while managing sudden and unexpected postural transitions of increasing intensities. Accordingly, results corroborate the hypothesis that balance control emerges from a governing set of biomechanical invariants, that is, suitable control schemes (e.g., planar covariation law) shared across voluntary and corrective motor behaviors, and across different sensory contexts due to different perturbation intensities, in both younger and older subjects. In this respect, our findings provide further support to investigate the effects of specific task training programs to counteract the risk of fall. This study was aimed at investigating how aging affects the intralimb coordination of lower limb segments, described by the planar covariation law, during unexpected slip-like perturbations of increasing intensity. Results revealed that neither the aging nor the perturbation intensity affects this coordination strategy. Accordingly, we proposed that the balance control emerges from an invariant set of control schemes shared across different sensory motor contexts and despite age-related neuromuscular adaptations.
本研究旨在验证衰老是否会改变在跑步机上稳定行走时由意外滑倒样扰动引发的纠正反应过程中的肢体内部协调策略。为此，招募了10名年轻受试者和10名老年受试者，要求他们应对不同强度的意外滑倒。我们使用主成分分析来分析下肢各节段的平面协变规律，以验证老年受试者在扰动前后各节段的仰角是否沿同一平面协变。结果表明，无论何种扰动，年轻和老年受试者受扰动肢体的节段均不协变。相反，未受扰动肢体的平面协变规律在年轻和老年受试者中都系统地保持着。尽管在组间和扰动强度方面观察到了时空和运动学参数的差异，但仍出现了这些结果。总体而言，我们的分析表明，衰老不会影响滑倒样扰动引发的纠正反应过程中的肢体内部协调，这表明年轻和老年受试者在应对强度不断增加的突然和意外姿势转变时都采用了这种控制策略。因此，研究结果证实了这样一种假设，即平衡控制源自一组主导的生物力学不变量，也就是说，在年轻和老年受试者中，适用于自愿和纠正性运动行为以及不同感觉情境（由于不同的扰动强度）的合适控制方案（例如平面协变规律）。在这方面，我们的研究结果为进一步研究特定任务训练计划对降低跌倒风险的影响提供了支持。本研究旨在调查在强度不断增加的意外滑倒样扰动过程中，衰老如何影响由平面协变规律描述的下肢节段的肢体内部协调。结果显示，衰老和扰动强度均不影响这种协调策略。因此，我们提出平衡控制源自一组在不同感觉运动情境中共享的不变控制方案，且不受与年龄相关的神经肌肉适应性影响。
