Park Seoung Hoon, Casamento-Moran Agostina, Yacoubi Basma, Christou Evangelos A
Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, 32611, USA.
Department of Physical Therapy, University of Florida, Gainesville, FL, USA.
Exp Brain Res. 2017 Sep;235(9):2717-2727. doi: 10.1007/s00221-017-5005-5. Epub 2017 Jun 12.
Visual feedback can influence the force output by changing the power in frequencies below 1 Hz. However, it remains unknown whether visual guidance can help an individual reduce force variability voluntarily. The purpose of this study, therefore, was to determine whether an individual can voluntarily reduce force variability during constant contractions with visual guidance, and whether this reduction is associated with a decrease in the power of low-frequency oscillations (0-1 Hz) in force and muscle activity. Twenty young adults (27.6 ± 3.4 years) matched a force target of 15% MVC (maximal voluntary contraction) with ankle dorsiflexion. Participants performed six visually unrestricted contractions, from which we selected the trial with the least variability. Following, participants performed six visually guided contractions and were encouraged to reduce their force variability within two guidelines (±1 SD of the least variable unrestricted trial). Participants decreased the SD of force by 45% (P < 0.001) during the guided condition, without changing mean force (P > 0.2). The decrease in force variability was associated with decreased low-frequency oscillations (0-1 Hz) in force (R = 0.59), which was associated with decreased low-frequency oscillations in EMG bursts (R = 0.35). The reduction in low-frequency oscillations in EMG burst was positively associated with power in the interference EMG from 35 to 60 Hz (R = 0.47). In conclusion, voluntary reduction of force variability is associated with decreased low-frequency oscillations in EMG bursts and consequently force output. We provide novel evidence that visual guidance allows healthy young adults to reduce force variability voluntarily likely by adjusting the low-frequency oscillations in the neural drive.
视觉反馈可通过改变低于1赫兹频率的功率来影响力量输出。然而，视觉引导是否能帮助个体自主降低力量变异性仍不清楚。因此，本研究的目的是确定个体在视觉引导下进行持续收缩时是否能自主降低力量变异性，以及这种降低是否与力量和肌肉活动中低频振荡（0 - 1赫兹）的功率降低有关。20名年轻成年人（27.6 ± 3.4岁）通过踝关节背屈来匹配15%最大自主收缩（MVC）的力量目标。参与者进行了6次无视觉限制的收缩，从中我们选择了变异性最小的试验。随后，参与者进行了6次视觉引导的收缩，并被鼓励在两个指导范围内（最不变异的无限制试验的±1标准差）降低他们的力量变异性。在引导条件下，参与者将力量的标准差降低了45%（P < 0.001），而平均力量没有变化（P > 0.2）。力量变异性的降低与力量中低频振荡（0 - 1赫兹）的降低相关（R = 0.59），这又与肌电图爆发中的低频振荡降低相关（R = 0.35）。肌电图爆发中低频振荡的降低与35至60赫兹的干扰肌电图功率呈正相关（R = 0.47）。总之，力量变异性的自主降低与肌电图爆发中低频振荡的降低以及力量输出的降低相关。我们提供了新的证据，即视觉引导可能通过调节神经驱动中的低频振荡使健康年轻成年人自主降低力量变异性。
