School of Physiotherapy, Curtin University, Shenton Park, W. Australia 6008, Australia.
J Electromyogr Kinesiol. 1993;3(4):236-44. doi: 10.1016/1050-6411(93)90013-M.
Analysis of functional movements using surface electromyography (EMG) often involves recording both eccentric and concentric muscle activity during a stretch-shorten cycle (SSC). The techniques used for amplitude normalization are varied and are independent of the type of muscle activity involved. The purpose of this study was: (i) to determine the effect of 11 amplitude normalization techniques on the coefficient of variation (CV) during the eccentric and concentric phases of the SSC; and (ii) to establish the effect of the normalization techniques on the EMG signal under variable load and velocity. The EMG signal of the biceps brachii of eight normal subjects was recorded under four SSC conditions and three levels of isometric contraction. The 11 derived normalization values were total rms, mean rms and peak rms (100 ms time constant) for the isometric contractions and the mean rms and peak rms values of the ensemble values for each set of isotonic contractions. Normalization using maximal voluntary isometric contractions (MVIC), irrespective of rms processing (total, mean or peak), demonstrated greater CV above the raw data for both muscle actions. Mean ensemble values and submaximal isometric recordings reduced the CV of concentric data. No amplitude normalization technique reduced the CV for eccentric data under loaded conditions. An ANOVA demonstrated significant (P < 0.01) main effects for load and velocity on concentric raw data and an interaction (P < 0.05) for raw eccentric data. No significant effects were demonstrated for changes in velocity when the data were normalized using mean rms values. The reduction of the CV should not be at the expense of true biological variance and current normalization techniques poorly serve the analysis of eccentric muscle activity during the SSC.
使用表面肌电图（EMG）分析功能性运动时，通常需要在拉伸-缩短循环（SSC）期间记录离心和向心肌肉活动。幅度归一化所使用的技术多种多样，与所涉及的肌肉活动类型无关。本研究的目的是：（i）确定 11 种幅度归一化技术对 SSC 离心和向心阶段 CV 的影响；（ii）确定归一化技术对在变负荷和速度下的 EMG 信号的影响。对 8 名正常受试者的肱二头肌进行 EMG 信号记录，共涉及 4 种 SSC 条件和 3 种等长收缩水平。这 11 种归一化值是等长收缩的总均方根（rms）、平均 rms 和峰值 rms（100ms 时间常数），以及各等张收缩集的均方根和峰值 rms 值。使用最大自主等长收缩（MVIC）进行归一化，不论 rms 处理（总、平均或峰值），对于两种肌肉运动，原始数据的 CV 都更高。平均集合值和亚最大等长记录降低了向心数据的 CV。在加载条件下，没有幅度归一化技术可以降低离心数据的 CV。ANOVA 表明，负荷和速度对向心原始数据有显著的（P < 0.01）主效应，对原始离心数据有交互作用（P < 0.05）。当使用平均 rms 值对数据进行归一化时，速度的变化没有表现出显著的影响。CV 的降低不应以真实生物方差为代价，而目前的归一化技术在分析 SSC 期间的离心肌肉活动方面表现不佳。
