School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney, Camperdown, New South Wales, Australia.
Neuroscience Research Australia (NeuRA), Sydney, New South Wales, Australia.
PLoS One. 2022 Nov 21;17(11):e0277947. doi: 10.1371/journal.pone.0277947. eCollection 2022.
In human applied physiology studies, the amplitude of recorded muscle electromyographic activity (EMG) is often normalized to maximal EMG recorded during a maximal voluntary contraction. When maximal contractions cannot be reliably obtained (e.g. in people with muscle paralysis, anterior cruciate ligament injury, or arthritis), EMG is sometimes normalized to the maximal compound muscle action potiential evoked by stimulation, the Mmax. However, it is not known how these two methods of normalization affect the conclusions and comparability of studies. To address this limitation, we investigated the relationship between voluntary muscle activation and EMG normalized either to maximal EMG or to Mmax. Twenty-five able-bodied adults performed voluntary isometric ankle plantarflexion contractions to a range of percentages of maximal voluntary torque. Ankle torque, plantarflexor muscle EMG, and voluntary muscle activation measured by twitch interpolation were recorded. EMG recorded at each contraction intensity was normalized to maximal EMG or to Mmax for each plantarflexor muscle, and the relationship between the two normalization approaches quantified. A slope >1 indicated EMG amplitude normalized to maximal EMG (vertical axis) was greater than EMG normalized to Mmax (horizontal axis). Mean estimates of the slopes were large and had moderate precision: soleus 8.7 (95% CI 6.9 to 11.0), medial gastrocnemius 13.4 (10.5 to 17.0), lateral gastrocnemius 11.4 (9.4 to 14.0). This indicates EMG normalized to Mmax is approximately eleven times smaller than EMG normalized to maximal EMG. Normalization to maximal EMG gave closer approximations to the level of voluntary muscle activation assessed by twitch interpolation.
在人类应用生理学研究中，记录的肌肉肌电图（EMG）幅度通常被归一化为最大自愿收缩期间记录的最大 EMG。当无法可靠地获得最大收缩时（例如在肌肉麻痹、前交叉韧带损伤或关节炎患者中），EMG 有时会被归一化为刺激引起的最大复合肌肉动作电位，即 Mmax。然而，尚不清楚这两种归一化方法如何影响研究的结论和可比性。为了解决这一限制，我们研究了自愿肌肉激活与归一化为最大 EMG 或 Mmax 的 EMG 之间的关系。25 名健康成年人进行了一系列自愿等长踝关节跖屈收缩，达到最大自愿扭矩的百分比。记录踝关节扭矩、跖屈肌 EMG 和通过抽搐插值测量的自愿肌肉激活。将每个收缩强度下记录的 EMG 归一化为每个跖屈肌的最大 EMG 或 Mmax，并量化两种归一化方法之间的关系。斜率>1 表示归一化为最大 EMG（纵轴）的 EMG 幅度大于归一化为 Mmax（横轴）的 EMG。斜率的平均估计值较大，精度适中：比目鱼肌 8.7（95%CI 6.9 至 11.0）、内侧腓肠肌 13.4（10.5 至 17.0）、外侧腓肠肌 11.4（9.4 至 14.0）。这表明归一化为 Mmax 的 EMG 大约是归一化为最大 EMG 的 EMG 的十一倍。归一化为最大 EMG 更接近抽搐插值评估的自愿肌肉激活水平。
