Ibitoye Morufu Olusola, Hamzaid Nur Azah, Hasnan Nazirah, Abdul Wahab Ahmad Khairi, Islam Md Anamul, Kean Victor S P, Davis Glen M
Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia; Department of Biomedical Engineering, Faculty of Engineering and Technology, University of Ilorin, P. M. B. 1515 Ilorin, Nigeria.
Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia.
Med Eng Phys. 2016 Aug;38(8):767-75. doi: 10.1016/j.medengphy.2016.05.012. Epub 2016 Jun 8.
The interaction between muscle contractions and joint loading produces torques necessary for movements during activities of daily living. However, during neuromuscular electrical stimulation (NMES)-evoked contractions in persons with spinal cord injury (SCI), a simple and reliable proxy of torque at the muscle level has been minimally investigated. Thus, the purpose of this study was to investigate the relationships between muscle mechanomyographic (MMG) characteristics and NMES-evoked isometric quadriceps torques in persons with motor complete SCI. Six SCI participants with lesion levels below C4 [(mean (SD) age, 39.2 (7.9) year; stature, 1.71 (0.05) m; and body mass, 69.3 (12.9) kg)] performed randomly ordered NMES-evoked isometric leg muscle contractions at 30°, 60° and 90° knee flexion angles on an isokinetic dynamometer. MMG signals were detected by an accelerometer-based vibromyographic sensor placed over the belly of rectus femoris muscle. The relationship between MMG root mean square (MMG-RMS) and NMES-evoked torque revealed a very high association (R(2)=0.91 at 30°; R(2)=0.98 at 60°; and R(2)=0.97 at 90° knee angles; P<0.001). MMG peak-to-peak (MMG-PTP) and stimulation intensity were less well related (R(2)=0.63 at 30°; R(2)=0.67 at 60°; and R(2)=0.45 at 90° knee angles), although were still significantly associated (P≤0.006). Test-retest interclass correlation coefficients (ICC) for the dependent variables ranged from 0.82 to 0.97 for NMES-evoked torque, between 0.65 and 0.79 for MMG-RMS, and from 0.67 to 0.73 for MMG-PTP. Their standard error of measurements (SEM) ranged between 10.1% and 31.6% (of mean values) for torque, MMG-RMS and MMG-PTP. The MMG peak frequency (MMG-PF) of 30Hz approximated the stimulation frequency, indicating NMES-evoked motor unit firing rate. The results demonstrated knee angle differences in the MMG-RMS versus NMES-isometric torque relationship, but a similar torque related pattern for MMG-PF. These findings suggested that MMG was well associated with torque production, reliably tracking the motor unit recruitment pattern during NMES-evoked muscle contractions. The strong positive relationship between MMG signal and NMES-evoked torque production suggested that the MMG might be deployed as a direct proxy for muscle torque or fatigue measurement during leg exercise and functional movements in the SCI population.
肌肉收缩与关节负荷之间的相互作用产生了日常生活活动中运动所需的扭矩。然而，在脊髓损伤（SCI）患者的神经肌肉电刺激（NMES）诱发收缩过程中，肌肉水平扭矩的简单可靠替代指标很少被研究。因此，本研究的目的是调查运动完全性SCI患者的肌肉机械肌电图（MMG）特征与NMES诱发的等长股四头肌扭矩之间的关系。六名病变水平低于C4的SCI参与者[（平均（标准差）年龄，39.2（7.9）岁；身高，1.71（0.05）米；体重，69.3（12.9）千克）]在等速测力计上，于30°、60°和90°膝关节屈曲角度下随机进行NMES诱发的等长腿部肌肉收缩。MMG信号由置于股直肌肌腹上的基于加速度计的振动肌电图传感器检测。MMG均方根（MMG-RMS）与NMES诱发扭矩之间的关系显示出非常高的相关性（膝关节角度为30°时R² = 0.91；60°时R² = 0.98；90°时R² = 0.97；P < 0.001）。MMG峰峰值（MMG-PTP）与刺激强度的相关性较差（膝关节角度为30°时R² = 0.63；60°时R² = 0.67；90°时R² = 0.45），尽管仍具有显著相关性（P≤0.006）。因变量的重测组内相关系数（ICC）对于NMES诱发扭矩范围为0.82至0.97，对于MMG-RMS为0.65至0.79，对于MMG-PTP为0.67至0.73。它们的测量标准误（SEM）对于扭矩、MMG-RMS和MMG-PTP在平均值的10.1%至31.6%之间。30Hz的MMG峰值频率（MMG-PF）接近刺激频率，表明NMES诱发的运动单位发放率。结果表明，MMG-RMS与NMES等长扭矩关系存在膝关节角度差异，但MMG-PF具有相似的扭矩相关模式。这些发现表明，MMG与扭矩产生密切相关，在NMES诱发的肌肉收缩过程中可靠地跟踪运动单位募集模式。MMG信号与NMES诱发扭矩产生之间的强正相关表明，MMG可能被用作SCI人群腿部运动和功能活动期间肌肉扭矩或疲劳测量的直接替代指标。
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