Introduction

The EMG filling factor is an index to quantify the degree to which an EMG signal has been filled. Here, we tested the validity of such index to analyse the EMG filling process as contraction force was slowly increased.

Methods

Surface EMG signals were recorded from the quadriceps muscles of healthy subjects as force was gradually increased from 0 to 40% MVC. The sEMG filling process was analyzed by measuring the EMG filling factor (calculated from the non-central moments of the rectified sEMG).

Results

(1) As force was gradually increased, one or two prominent abrupt jumps in sEMG amplitude appeared between 0 and 10% of MVC force in all the vastus lateralis and medialis.

(2) The jumps in amplitude were originated when a few large-amplitude MUPs, clearly standing out from previous activity, appeared in the sEMG signal.

(3) Every time an abrupt jump in sEMG amplitude occurred, a new stage of sEMG filling was initiated.

(4) The sEMG was almost completely filled at 2–12% MVC.

(5) The filling factor decreased significantly upon the occurrence of an sEMG amplitude jump, and increased as additional MUPs were added to the sEMG signal.

(6) The filling factor curve was highly repeatable across repetitions.

Conclusions

It has been validated that the filling factor is a useful, reliable tool to analyse the sEMG filling process. As force was gradually increased in the vastus muscles, the sEMG filling process occurred in one or two stages due to the presence of abrupt jumps in sEMG amplitude.

中文翻译：

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验证填充因子指数以研究股四头肌表面肌电信号的填充过程

介绍

肌电填充因子是量化肌电信号填充程度的指标。在这里，我们测试了该指标的有效性，以分析收缩力缓慢增加时的肌电图充盈过程。

方法

当力从 0% MVC 逐渐增加到 40% MVC 时，记录健康受试者股四头肌的表面 EMG 信号。通过测量肌电图填充因子（根据校正后的 sEMG 的非中心矩计算）来分析 sEMG 填充过程。

结果

(1)随着力的逐渐增加，所有股外侧肌和内侧肌在MVC力的0%到10%之间出现一到两次明显的sEMG振幅突变。

(2) 当 sEMG 信号中出现一些与先前活动明显不同的大幅度 MUP 时，就会产生幅度跳跃。

(3)每当sEMG振幅发生突然跳跃时，sEMG充盈的新阶段就开始。

(4) sEMG 在 2-12% MVC 时几乎完全充满。

(5) 填充因子在 sEMG 振幅跳跃发生时显着下降，并随着额外的 MUP 添加到 sEMG 信号而增加。

(6) 填充因子曲线在多次重复中具有高度可重复性。

结论

经验证，充盈因子是分析表面肌电充盈过程的有用且可靠的工具。随着股肌力量逐渐增加，由于 sEMG 振幅存在突然跳跃，sEMG 充盈过程发生在一或两个阶段。