Rannama Indrek, Zusa Anna, Latash Mark L
School of Natural Sciences and Health, Tallinn University, Narva Mnt 25, 10120, Tallinn, Estonia.
Kinesiology Research Laboratory, Latvian Academy of Sport Education, Riga, Latvia.
Exp Brain Res. 2023 May;241(5):1309-1318. doi: 10.1007/s00221-023-06608-7. Epub 2023 Mar 31.
We explored the phenomenon of unintentional force drift seen in the absence of visual feedback during knee extension contractions in isometric conditions. Based on the importance of knee extensors for the anti-gravity function, we hypothesized that such force drifts would be slower and smaller compared to those reported for the upper extremities. We also explored possible effects of foot dominance and gender on the force drifts. Young healthy persons produced isometric knee extension contractions to different levels, ranging from 15 to 25% of maximal voluntary contraction force, with the help of visual feedback, and then, the visual feedback was turned off. Force change over the time interval without visual feedback was quantified. In the absence of visual feedback, force drifted to smaller magnitudes. The drift magnitude expressed in percent of the initial force magnitude was smaller for smaller initial force levels, ranging between 8 and 15% of the initial force for the initial force magnitude of 15% and 25% of maximal voluntary contraction force. The time exponent of the force drift was independent of the initial force magnitude and was, on average, 6.45 s. There were no significant effects of foot dominance or gender, although the male subjects tended to show stronger scaling of the drift magnitude with the initial force level compared to the female subjects. The results show that unintentional force drift is a common phenomenon across limbs and muscle groups. This conclusion fits the theory of control with spatial referent coordinates and the general tendency of all natural systems to drift to states with lower potential energy.
我们探究了在等长条件下膝关节伸展收缩过程中，无视觉反馈时出现的无意用力漂移现象。鉴于膝伸肌对于抗重力功能的重要性，我们推测，与上肢相比，这种用力漂移会更慢且幅度更小。我们还探究了足部优势和性别对用力漂移可能产生的影响。年轻健康受试者在视觉反馈的帮助下，进行不同水平的等长膝关节伸展收缩，收缩力范围为最大自主收缩力的15%至25%，之后关闭视觉反馈。对无视觉反馈时间间隔内的力变化进行了量化。在无视觉反馈的情况下，力向较小幅度漂移。对于较小的初始力水平，以初始力大小的百分比表示的漂移幅度较小，当初始力大小为最大自主收缩力的15%和25%时，漂移幅度在初始力的8%至15%之间。力漂移的时间指数与初始力大小无关，平均为6.45秒。尽管男性受试者与女性受试者相比，倾向于表现出漂移幅度随初始力水平的缩放更强，但足部优势或性别均无显著影响。结果表明，无意用力漂移是四肢和肌肉群中的常见现象。这一结论符合空间参照坐标控制理论以及所有自然系统向势能较低状态漂移的一般趋势。
