Department of Clinical and Experimental Sciences, University of Brescia, Viale Europa, 11, 25123, Brescia, Italy.
Rehabilitation Service, Fondazione Teresa Camplani-Casa di Cura Domus Salutis, Via Lazzaretto, 3, 25123, Brescia, Italy.
Exp Brain Res. 2019 Aug;237(8):1889-1897. doi: 10.1007/s00221-019-05524-z. Epub 2019 May 16.
We investigated the influence of the ageing process on the performance of the motor control system accuracy during a challenging motor task throughout the analysis of force output oscillations. The force signal of the first dorsal interosseous during linearly varying static contraction, 0-100-0% of the maximal volitional abduction in 15 s, was studied in 11 young and older adults. The relative error between the target and the actual force as well as several parameters of the force oscillations (corrections) were estimated. To understand the experimental results, we analyzed the force output generated by a set of computational simulations of a pool of motor units controlled by a proportional-integral-derivative system. Compared to young adults the older subjects presented larger errors and a lower number of corrections with longer duration and larger relative amplitude. The motor control system modelling varied the error update frequency (UF) of the controller (from 1 to 2.5 Hz) as well as the range of contraction time (CT) of the recruited motor unit (30-90 ms and 60-120 ms reflecting young and old ranges, respectively). The simulation generated force profiles with parameters similar to experimental recordings in young (UF = 1.5; CT 30-90 ms) and older (UF = 1; CT 60-120 ms) adults. Interestingly, the results of the simulations suggested that the improvement in the error update frequency of the controller was not able to compensate for the contractile changes in the motor unit twitches. In conclusion, the peripheral contractile changes with age can influence motor unit control strategies and represent a crucial phenomenon in the generation of larger force oscillations in older adults.
我们通过分析力输出的振荡，研究了在具有挑战性的运动任务中，衰老过程对运动控制系统准确性的影响。在 15 秒内，通过线性变化的静态收缩，将第一背侧骨间肌从 0%最大随意外展增加到 100%最大随意外展，研究了 11 名年轻和老年成年人的力信号。估计了力信号的相对误差（目标力与实际力之间的差异）以及力振荡的几个参数（校正）。为了理解实验结果，我们分析了一组由比例积分微分系统控制的运动单位池产生的力输出的计算模拟。与年轻人相比，老年人的误差更大，校正次数更少，校正持续时间更长，相对幅度更大。运动控制系统建模改变了控制器的误差更新频率（UF）（从 1 到 2.5 Hz）以及募集运动单位的收缩时间范围（CT）（30-90 ms 和 60-120 ms，分别反映年轻和老年范围）。模拟产生的力曲线参数与年轻人（UF = 1.5；CT 30-90 ms）和老年人（UF = 1；CT 60-120 ms）的实验记录相似。有趣的是，模拟结果表明，控制器的误差更新频率的提高并不能弥补运动单位抽搐的收缩变化。总之，随着年龄的增长，外周收缩变化会影响运动单位的控制策略，并且是老年人产生更大力振荡的关键现象。
