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Wearable measuring system has major effects on biomechanics of human movements especially in daily activities in order to monitor and analyze the human movements to achieve the most important kinematics parameters. In the recent decade, inertial sensors were utilized by researchers in order to developing wearable system for instrumentation of human movements. In this study, Sharif-Human Movement Instrumentation System (SHARIF-HMIS) was designed and manufactured. The system consists of inertial measurement units (IMUs), stretchable clothing and data logger. The IMU sensors are installed on the human body. The system can be used at home and also industrial environments. The main features of this system are: low cost, low weight, saving data for ten hours and being wearable. Furthermore, the software was designed for data acquisition of the IMUs.

This paper presents the background of low back problem caused by repetitive fatigue loading. We emphasize on mechanism of Intervertebral Disc (IVD) and conditions for which the disc does not recover its original status under repetitive work and cause low back pain. The objective of this study is to identify structural changes in system parameters for fatigue loaded intervertebral disc. Principal component analysis (PCA) is used for studying the behavioral change of spine against cyclic loading as a function of time. Percentage difference and similarity factor was calculated for the analysis. Specimens were applied with impulse testing to measure the stiffness and acceleration after fracture, augmentation and fatigue loading. The fatigue loading were 650N, 950N and 1150N at 5Hz for 1, 2, 3, 4 and 5 hours. 12 hours rest was given between different loadings. Based on PCA analysis, it is observed that IVD does not restore to original condition after 50 minutes of fatigue loading. In addition, if people set load at range between 30 to 50 minutes, vertebra discs cannot fully return to the normal position anymore depending on total load. Vertebra can support load as much as 0.5kN limited to 30 to 50 minutes. It implies that fracture may occur. Rest is very important in order to prevent the deformity and abnormalities of backbone discs. We found that in spine vertebral acceleration and displacement are dependent on the applied force.

Wearable system is a proper solution for rehabilitation and instrumentation applications for human daily activities. Recently, several researches are concentrated on this technology significantly because of new progress in sensors and fusion sensors. In the near future, wearable and ambulatory devices will be used considerably in biomedical applications. In this study, we reviewed some methods about wearable measuring system then introduced and designed innovative wearable clothing for this purpose. Some specifications and advantages of our system in comparison with relevant researches are; using painted sensors that are manufactured through nano electro active polymer technology, low weight, low price, applicable for daily activity, three dimensional detection of human body movements and noninvasive. We utilized textile sensor to measure the trunk movements in three dimensions. Twenty textile sensors were attached on the clothing in this version of system. In addition to wearable system, clothing was prepared in order to determine the positions of textile sensors on the body. Furthermore, an electronic board is developed for data acquisition and transfer data to computer real-time. Finally, the wearable clothing for ambulatory purposes was manufactured and also different methods for the system calibration have been presented.

Prevalence of LBP has led researchers to find out biomechanics of lumbar spine in conjunction with the surrounding muscles and the role of intra-abdominal pressure in different activities. Despite substantial number of experimental studies in this field, limitations of in-vivo experiments have guided researchers to utilize mathematical modeling to obtain more information regarding the spine biomechanics. An important aspect of such spinal modeling is to replicate the muscle behavior which includes nonlinear mechanical properties. In this study, we developed a finite element model of the spine with the surrounding muscles consisting both active and passive behavior of the muscles at the same time. In order to have more realistic muscles, we used the combination of a 1-D nonlinear element and a 2-D linear elastic shell. The shell element can take initial stress, while the 1-D element can take force-displacement relationship. For each muscle, 1-D elements were laid on shell elements in the direction of muscle fibers. In a specific activity level, initial stress and stiffness of shell elements and force-displacement relation of 1-D elements were changed based on mathematical model of muscles published in the literature. The effects of two muscles of the model were investigated on lumbar spine and IAP. These muscles are rectus abdominis and transversus abdominis. Results show that TA has an important effect on IAP generation and this muscle can produce extensor moment due to increasing IAP. RA has flexor role and has no important effect on IAP. Also analyses have predicted a reduction in lumbar spine compression force with increasing IAP.

The complexity associated with musculoskeletal modeling, simulation, and neural control of the human spine is a challenging problem in the field of biomechanics. This paper presents a novel method for simulation of a 3D trunk model under control of 48 muscle actuators. Central pattern generators (CPG) and artificial neural network (ANN) are used simultaneously to generate muscles activation patterns. The parameters of the ANN are updated based on a novel learning method used to address the kinetic redundancy due to presence of 48 muscles driving the trunk. We demonstrated the feasibility of the proposed method with numerical simulation of experiments involving rhythmic motion between upright standing and 55 degrees of flexion. The tracking performance of the model is accurate to within 2° while reciprocal muscle activation patterns were similar to the observed experimental coordination patterns in normal subjects. The suggested method can be used to map high-level control strategies to low-level control signals in complex biomechanical and biorobotic systems. This will also provide insight about underlying neural control mechanisms.

This paper uses singular value decomposition (SVD) for studying the dynamic properties of fatigue-loaded intervertebral disc. Previously, this problem had been addressed using mathematical models of using mass, spring and damper or based on poroelastic theory. This paper utilizes the signal processing approach and attempts to describe SVD based feature that can be an indicator for change in behavioral performance of the intervertebral disc warning the occurrence of temporary or permanent change in the structure or abnormality in behavior. The results are encouraging; however, further validation is required with more data.

A central problem in motor control is to understand how the many biomechanical degrees of freedom are coordinated to achieve a goal. A common assumption is that Central Nervous System (CNS) will plan tasks based on open-loop optimal control theory which simultaneously predicts state variables and motor commands based on a compound objective function. A 3D computational method incorporated with 18 anatomically oriented muscles is used to simulate human trunk system. Direct collocation method allows us to convert a constrained optimal control problem to a common nonlinear programming problem to assume the spinal stability condition. Trunk movement from the upright standing to 60 degrees of flexion is simulated based on this method. Incorporation of the stability condition with the open-loop optimal controller resulted in an increase of antagonistic activities which would increase the joint stiffness around the Lumbosacral joint in response to gravity perturbation. Results showed that different patterns of trunk movement and back muscles activity can be explained based on change in the coefficient of two performance indices.

In this study, posture and spinal stability were evaluated during a manual task in a standing posture on a movable scaffold at two levels of heights, with and without safety handrails between experts and novice construction workers using insole pressure transducers and muscle activities of trunk muscles. Eight construction workers (4 experts and 4 novices) working at a construction site participated in the experiment for ergonomic assessment. A significant difference was found in postural stability, spinal stability with regard to career (p

The role of motor control in development of low back pain is subject of many researches both in theoretical and experimental fields. In this work flexion-extension movement of lumbar spine have been controlled by three different methods, including feedback linearization (FBL), PD control and their combinations. The model involves 7 links: 1 link for pelvis, 5 links for lumbar vertebrae and 1 link for trunk. Torque actuators have been used on each joint to make them follow desired trajectory. In linear control method, equations of motion have been linearized with respect to upright position and then control signals have been applied in the direction of eigenvectors. Robustness of each method against noises, sensory delay and parameters uncertainty have been investigated. Desired trajectory of each joint has been produced by Central Pattern Generators (CPGs), which was the subject of our previous work. The results show that PD controller in comparison with feedback linearization method is more robust in presence of noise and parameters uncertainty, but FBL controller is better when we have sensory delay. Combination of these methods leads to better control in all three simulations.

Robot-mediated rehabilitation is a rapidly advancing discipline that seeks to develop improved treatment procedures using new technologies, e.g., robotics, coupled with modern theories in neuroscience and rehabilitation. A robotic device was designed and developed for rehabilitation of upper limbs of post stroke patients. A novel force feedback bimanual working mode provided real-time dynamic sensation of the paretic hand. Results of the preliminary clinical tests revealed a quantitative evaluation of the patient's level of paresis and disability.

Twelve subjects performed a fatiguing repetitive lift in the sagittal plane until exhaustion to discover the effect of fatigue on changes in kinematics, postural stability, and coordination. A load equal to 25% of the subjects' isoinertial lifting capacity was repetitively lifted and lowered at a maximal lifting rate from mid-tibia to waist height. Knee and hip range of motion were significantly decreased, while peak trunk flexion increased at the end of the task. Postural stability decreased and subjects extended their knee, hip and spine earlier in the lifting phase, at the end of the task. Some of these adaptations are indicative of mechanisms that may cause increased loading of the passive tissues of the spine and hence increased risk of injury, while others need to be investigated further.

The structures observed in humans are being progressively applied to the theoretical approaches developed in robotics. To gain insight to the intricate mechanism of human motion, researchers sometimes use imaging technology to record the trajectories of humans performing various tasks. From these observations, they are able to estimate the forces and moments at each joint by an inverse dynamics computation. This problem is conceptually simple; however, in practice, the inverse solution requires the calculation of higher order derivatives of experimental observations contaminated by noise. The errors due to differentiation results in erroneous joint force and moment calculations. This paper provide a control theoretic framework for analyzing human motion which avoids derivative computations. The method is also suitable for synthesis of stable controllers for robotic and 'biorobic' applications which require tracking a desired reference trajectory under different loading conditions.

Feature extraction and stepwise discrimination techniques were applied to motion profiles (MPs) obtained from subjects during a repetitive trunk flexion and extension task, in order to develop a computer aided procedure for the diagnosis of low back disorder. 524 subjects, belonging to normal, low back pain patient, and pre-employment categories were tested using the B-200 Isostation dynamometers, at the Mayo Clinic and The Ohio State University. Principal components analysis (PCA) and Fourier descriptor (FD) methods were used to efficiently represent the continuous MPs and phase portraits, respectively, by reducing the dimensionality of the data. In addition, the statistical parameters from the continuous MPs were used to represent the dynamic trunk performance. The results of discriminant analysis indicated similar error rates ranging from 19% to 24%, using the three methods of data representation: MPs, PCA and FD.