Azghani M R, Farahmand F, Meghdari A, Vossoughi G, Parnianpour M
Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran.
Proc Inst Mech Eng H. 2009 Aug;223(6):755-66. doi: 10.1243/09544119JEIM537.
Maximal strength measurements of the trunk have been used to evaluate the maximum functional capacity of muscles and the potential mechanical overload or overuse of the lumbar spine tissues in order to estimate the risk of developing musculoskeletal injuries. A new triaxial isometric trunk strength measurement system was designed and developed in the present study, and its reliability and performance was investigated. The system consisted of three main revolute joints, equipped with torque sensors, which intersect at L5-S1 and adjustment facilities to fit the body anthropometry and to accommodate both symmetric and asymmetric postures in both seated and standing positions. The dynamics of the system was formulated to resolve validly the moment generated by trunk muscles in the three anatomic planes. The optimal gain and offset of the system were obtained using deadweights based on the least-squares linear regression analysis. The R2 results of calibration for all loading courses of all joints were higher than 0.99, which indicated an excellent linear correlation. The results of the validation analysis of the regression model suggested that the mean absolute error and the r.m.s. error were less than 2 per cent of the applied load. The maximum value of the minimum detectable change was found to be 1.63 Nm for the sagittal plane torque measurement, 0.8 per cent of the full-scale load. The trial-to-trial variability analysis of the device using deadweights provided intra-class correlation coefficients of higher than 0.99, suggesting excellent reliability. The cross-talk analysis of the device indicated maximum cross-talks of 1.7 per cent and 3.4 per cent when the system was subjected to flexion-extension and lateral bending torques respectively. The trial-to-trial variability of the system during in-vivo strength measurement tests resulted in good to excellent reliability, with intra-class correlation coefficients ranging from 0.69 to 0.91. The results of the maximum voluntary isometric torques exertion measurements for 30 subjects indicated good agreement with the previously published data in the literature. The extensive capabilities and high reliability of the system are promising for more comprehensive investigations on the trunk biomechanics in future, e.g. isometric strength measurement at symmetric and asymmetric postures, muscle endurance, and recruitment pattern analysis.
躯干最大力量测量已被用于评估肌肉的最大功能能力以及腰椎组织潜在的机械过载或过度使用情况，以便估计发生肌肉骨骼损伤的风险。在本研究中设计并开发了一种新的三轴等长躯干力量测量系统，并对其可靠性和性能进行了研究。该系统由三个主要的旋转关节组成，配备有扭矩传感器，这些关节在L5 - S1处相交，并设有调整装置以适应人体测量学特征，并能适应坐姿和站姿下的对称和不对称姿势。该系统的动力学方程被制定出来，以有效求解躯干肌肉在三个解剖平面上产生的力矩。基于最小二乘线性回归分析，使用自重获得了系统的最佳增益和偏移量。所有关节所有加载过程的校准R2结果均高于0.99，这表明具有良好的线性相关性。回归模型的验证分析结果表明，平均绝对误差和均方根误差小于施加负荷的2%。矢状面扭矩测量的最小可检测变化的最大值为1.63 Nm，占满量程负荷的0.8%。使用自重对该装置进行的逐次试验变异性分析提供了高于0.99的组内相关系数，表明可靠性极佳。该装置的串扰分析表明，当系统分别受到屈伸和侧弯扭矩作用时，最大串扰分别为1.7%和3.4%。在活体力量测量测试期间，该系统的逐次试验变异性产生了良好到极佳的可靠性，组内相关系数范围为0.69至0.91。对30名受试者进行的最大自主等长扭矩施加测量结果表明，与文献中先前发表的数据吻合良好。该系统的广泛功能和高可靠性为未来对躯干生物力学进行更全面的研究带来了希望，例如对称和不对称姿势下的等长力量测量、肌肉耐力和募集模式分析。
