Zhou S, Lawson D L, Morrison W E, Fairweather I
Department of Physical Education and Recreation, Victoria University of Technology, Melbourne, Australia.
Eur J Appl Physiol Occup Physiol. 1995;70(2):138-45. doi: 10.1007/BF00361541.
Electromechanical delay (EMD) in isometric contractions of knee extensors evoked by voluntary, tendon reflex (TR) and electrical stimulation (ES) was investigated in 21 healthy young subjects. The subject performed voluntary knee extensions with maximum effort (maximal voluntary contraction, MVC), and at 30%, 60% and 80% MVC. Patellar tendon reflexes were evoked with the reflex hammer being dropped from 60 degrees, 75 degrees and 90 degrees positions. In the percutaneous ES evoked contractions, single switches were triggered with pulses of duration 1.0 ms and of intensities 90, 120 and 150 V. Electromyograms of the vastus lateralis and rectus femoris muscles were recorded using surface electrodes. The isometric knee extension force was recorded using a load cell force transducer connected to the subject's lower leg. The major finding of this study was that EMD of the involuntary contractions [e.g. mean 22.1 (SEM 1.32) ms in TR 90 degrees; mean 17.2 (SEM 0.62) ms in ES 150 V] was significantly shorter than that of the voluntary contractions [e.g. mean 38.7 (SEM 1.18) ms in MVC, P < 0.05]. The relationships between EMD, muscle contractile properties and muscle fibre conduction velocity were also investigated. Further study is needed to explain fully the EMD differences found between the voluntary and involuntary contractions.
在21名健康年轻受试者中，研究了由自愿收缩、腱反射（TR）和电刺激（ES）诱发的膝关节伸肌等长收缩中的机电延迟（EMD）。受试者以最大努力进行自愿膝关节伸展（最大自主收缩，MVC），以及在30%、60%和80%MVC水平下进行。用反射锤从60度、75度和90度位置落下诱发髌腱反射。在经皮电刺激诱发的收缩中，用持续时间为1.0毫秒、强度为90、120和150伏的脉冲触发单个开关。使用表面电极记录股外侧肌和股直肌的肌电图。使用连接到受试者小腿的测力传感器记录等长膝关节伸展力。本研究的主要发现是，非自愿收缩的EMD[例如，在90度TR时平均为22.1（标准误1.32）毫秒；在150伏ES时平均为17.2（标准误0.62）毫秒]明显短于自愿收缩的EMD[例如，在MVC时平均为38.7（标准误1.18）毫秒，P<0.05]。还研究了EMD、肌肉收缩特性和肌纤维传导速度之间的关系。需要进一步研究以充分解释在自愿收缩和非自愿收缩之间发现的EMD差异。
