Poirier Gabriel, Papaxanthis Charalambos, Mourey France, Gaveau Jeremie
INSERM UMR1093-CAPS, Université Bourgogne Franche-Comté, UFR des Sciences du Sport, Dijon, France.
Front Aging Neurosci. 2020 Feb 25;12:37. doi: 10.3389/fnagi.2020.00037. eCollection 2020.
Several sensorimotor modifications are known to occur with aging, possibly leading to adverse outcomes such as falls. Recently, some of those modifications have been proposed to emerge from motor planning deteriorations. Motor planning of vertical movements is thought to engage an internal model of gravity to anticipate its mechanical effects on the body-limbs and thus to genuinely produce movements that minimize muscle effort. This is supported, amongst other results, by direction-dependent kinematics where relative durations to peak accelerations and peak velocity are shorter for upward than for downward movements. The present study compares the motor planning of fast and slow vertical arm reaching movements between 18 young (24 ± 3 years old) and 17 older adults (70 ± 5 years old). We found that older participants still exhibit strong directional asymmetries (i.e., differences between upward and downward movements), indicating that optimization processes during motor planning persist with healthy aging. However, the size of these differences was increased in older participants, indicating that gravity-related motor planning changes with age. We discuss this increase as the possible result of an overestimation of gravity torque or increased weight of the effort cost in the optimization process. Overall, these results support the hypothesis that feedforward processes and, more precisely, optimal motor planning, remain active with healthy aging.
已知随着年龄增长会出现一些感觉运动方面的改变，这可能会导致跌倒等不良后果。最近，有人提出其中一些改变是由运动计划恶化引起的。垂直运动的运动计划被认为涉及重力的内部模型，以预测其对身体肢体的机械影响，从而真正产生使肌肉努力最小化的运动。除其他结果外，方向依赖运动学也支持这一点，即向上运动达到峰值加速度和峰值速度的相对持续时间比向下运动短。本研究比较了18名年轻人（24±3岁）和17名老年人（70±5岁）快速和慢速垂直手臂伸展运动的运动计划。我们发现，老年参与者仍然表现出强烈的方向不对称性（即向上和向下运动之间的差异），这表明运动计划过程中的优化过程在健康衰老过程中仍然存在。然而，这些差异的大小在老年参与者中有所增加，这表明与重力相关的运动计划会随着年龄而变化。我们将这种增加讨论为优化过程中重力扭矩估计过高或努力成本增加的可能结果。总体而言，这些结果支持了这样一种假设，即前馈过程，更确切地说是最佳运动计划，在健康衰老过程中仍然活跃。
