Wee A S
Electromyography Laboratory, Department of Neurology, University of Mississippi Medical Center, Jackson, Mississippi 39216, USA.
Electromyogr Clin Neurophysiol. 2006 Mar-Apr;46(2):79-82.
This study was to determine if the size of the compound muscle action potential (CMAP) recorded from a large muscle, such as the biceps brachii, can be correlated with the muscle mass or volume that is generating the electrical response. Supramaximal CMAPs were obtained from 32 normal biceps brachii muscles to electrical stimulation of the musculocutaneous nerve at the axilla. Upper-arm circumference was measured with biceps muscle relaxed (elbow extended) and during muscle contraction (elbow flexed). For all muscles, mean CMAP duration was 16.45 ms, amplitude was 10.50 mV, and area was 96.13 mVms. Body mass index and absolute upper-arm circumference (biceps muscle relaxed or contracted) did not correlate with CMAP duration, amplitude, and area; Pearson correlation coefficients (r) ranged from -0.24 to 0.16. However, the difference (increment) in upper-arm circumference due to biceps muscle contraction correlated with CMAP duration (r = 0.47), amplitude (r = 0.67), and area (r = 0. 75). CMAP size (amplitude and area) correlated well with biceps brachii muscle volume as estimated by the increase from baseline in upper-arm circumference during muscle contraction. The difference (increment) in upper-arm circumference due to biceps muscle contraction reflects mainly the underlying biceps muscle bulk, and eliminates other variables such as thickness of the subcutaneous tissues and triceps brachii muscle.
本研究旨在确定从诸如肱二头肌等大肌肉记录的复合肌肉动作电位（CMAP）的大小是否与产生电反应的肌肉质量或体积相关。在腋窝处对32条正常肱二头肌进行肌皮神经电刺激，获得超强CMAP。在肱二头肌放松（肘部伸展）和肌肉收缩（肘部屈曲）时测量上臂围。对于所有肌肉，平均CMAP持续时间为16.45毫秒，幅度为10.50毫伏，面积为96.13毫伏·秒。体重指数和绝对上臂围（肱二头肌放松或收缩时）与CMAP持续时间、幅度和面积均无相关性；皮尔逊相关系数（r）范围为-0.24至0.16。然而，肱二头肌收缩引起的上臂围差异（增加值）与CMAP持续时间（r = 0.47）、幅度（r = 0.67）和面积（r = 0.75）相关。CMAP大小（幅度和面积）与通过肌肉收缩期间上臂围相对于基线的增加所估计的肱二头肌体积密切相关。肱二头肌收缩引起的上臂围差异（增加值）主要反映了肱二头肌的潜在体积，并消除了其他变量，如皮下组织厚度和肱三头肌。
