Ferris-Hood K, Threlkeld A J, Horn T S, Shapiro R
Siskin Hospital for Physical Rehabilitation, Chattanooga, USA.
Electromyogr Clin Neurophysiol. 1996 Apr-May;36(3):157-70.
The purpose of this study was to quantify the time between the cessation of EMG activity and cessation of torque production, or relaxation electromechanical delay, (R-EMD) of the quadriceps at three angular movement velocities. A Biodex dynamometer passively moved the right knee of 25 males through a given range at three velocities (10, 60 and 120 degrees per second). Subjects were instructed to actively extend their knees to a visual target, then to immediately relax. Biodex torque and position data, as well as surface EMG from the right Vastus Medialis (VM), Rectus Femoris (RF) and Vastus Lateralis (VL) were sampled simultaneously. EMG cessation was determined when activity fell below a threshold based on the muscle's resting EMG. Torque cessation was determined when the slope of the relaxation curve decreased to 10% of the initial value. R-EMD time for each quadriceps head at each velocity was determined by calculating the difference between these two times. To examine reliability, subjects were retested four days later. Approximately two thirds of the subjects were unable to consistently perform the motor task of abrupt relaxation at some or all of the tested velocities. This variability was ascribed to motor control issues. Average R-EMD times for all subjects, muscle segments and velocities ranged from 249 +/- 68 ms to 276 +/- 51 ms during the first test session, and 239 +/- 46 ms to 300 +/- 59 ms during the second session. These data are important in identification of physiologically meaningful cessation of muscle contraction, and may be beneficial in research studies focusing on the areas of motor control and motor learning, computerized movement analysis, and prediction models for the determination of muscular force from the EMG signal.
本研究的目的是量化在三种角运动速度下，股四头肌肌电图（EMG）活动停止与扭矩产生停止之间的时间间隔，即放松肌电延迟（R-EMD）。一台Biodex测力计以三种速度（每秒10度、60度和120度）将25名男性的右膝被动移动通过给定范围。受试者被指示主动将膝盖伸展至视觉目标，然后立即放松。同时采集Biodex扭矩和位置数据，以及右侧股内侧肌（VM）、股直肌（RF）和股外侧肌（VL）的表面肌电图。当活动降至基于肌肉静息肌电图的阈值以下时，确定肌电图停止。当放松曲线的斜率降至初始值的10%时，确定扭矩停止。通过计算这两个时间之间的差值，确定每个速度下每个股四头肌头的R-EMD时间。为了检验可靠性，四天后对受试者进行重新测试。大约三分之二的受试者在部分或所有测试速度下无法始终如一地完成突然放松的运动任务。这种变异性归因于运动控制问题。在第一次测试期间，所有受试者、肌肉节段和速度的平均R-EMD时间范围为249±68毫秒至276±51毫秒，在第二次测试期间为239±46毫秒至300±59毫秒。这些数据对于识别肌肉收缩在生理上有意义的停止很重要，并且可能有助于专注于运动控制和运动学习、计算机化运动分析以及从肌电图信号确定肌肉力量的预测模型等领域的研究。
