Search

In this study, biomechanical characteristics during the whole process of gait initiation for twenty normal healthy volunteers were determined by the motion analysis with six near-infrared cameras, four forceplates, and an EMG system. Gait initiation, a transitional movement phenomenon from quiet stance to steady-state walking, involves a series of muscular activities, GRFs, movements of COP and COM, and joint motions. Results showed that the location of the net COP to be most lateral during double limb stance at the beginning of gait initiation. During gait initiation, changes in anteroposterior components of GRFs were first found and then changes in vertical components followed. Hip and knee motions were found before the ankle joint motion. Walking speed, step length, and stride length gradually increased until the second step. The interaction between the COM and COP is tightly regulated to control the trajectory of the COM and thereby control total body balance.

Recently, many studies have reported the fact that an excessively accumulated psychological and physical burden induced from physical labor conducted routinely in home and industry can be one of main reasons of musculoskeletal disorders in the working population. This fact makes increase interests in studies to reduce a risk of musculoskeletal disorders through grafting ergonomic considerations on working environment. However, there are currently limited methodologies in quantitative evaluations of new ergonomic suggestions to reduce a risk of musculoskeletal disorders. The current study is therefore performed to evaluate quantitatively effects of a design of washing machine as a new ergonomic suggestion onto prevention of musculoskeletal disorders, through application of a biomechanical evaluation methodology. For this, three-dimensional motion analysis by using musculoskeletal models with Rapid Entire Body Assessment (REBA), which has been generally used for a simple evaluation of a degree of harmfulness of the human body at specific working postures to be considered, was performed. The results of REBA did not give us enough information and their results were somewhat simple and inaccurate, but the results of the three-dimensional motion analysis give us enough information such as alteration of main muscle forces and joint moments required during washing work. All results showed that the main muscle strengths and joint moments were decreased effectively for reduction of a risk of musculoskeletal disorders during the washing work with newly designed washing machine evaluated in the current study, compared with those generated during the washing work with general washing machine. From these results, it can be concluded that a risk of the musculoskeletal disorders, which may be induced by a repetitive washing work, may be reduced through using the washing machine designed ergonomically and newly. Also, it is thought that if our ergonomic design can be applied for improvement of working environment in lifting and laying works conducted repeatedly for a treatment work of goods, which have a strong resemblance to the behaviors generated * 이 저서(논문·예술연구)는 2001학년도 연세대학교 학술연구비의 (부분적인) 지원에 의하여 이루어진 것임.

Gait initiation is a transitional process from the balanced upright standing to the beginning of steady-state walking. Steady-state walking represents the start of repeated gait pattern with steady-state walking speed within one gait cycle. Hemiplegic patients’ gait initiation was analyzed using the 3D motion analysis system synchronized with 2 force plates. The first vertex(V1) in the CoP trajectory was placed on the lateral-posterior point from the leading limb side, and the third vertex(V3) was placed on the lateral-anterior point from the trailing limb side in the CoP of the normal gait initiation. However, V1 was not nearly shown and V3 was placed on the posterior from the trailing limb side in the CoP of the hemiplegic gait initiation. The time and distance from the onset to the toe-off(P1) and from the toe-off to the initial contact( P2) were analyzed that the mean time was larger and the mean distance was shorter when the affected limb was leading limb. The net CoP data obtained on gait initiation with hemiplegic patients suggest that they compensated with different strategies with respect to the limb whether it was leading limb or trailing limb for their impairment.

This study investigated foot/ankle roll-over characteristics for different joint alignments of the ankle-foot orthosis(AFO). Seven volunteers without any musculoskeletal or foot problems participated in motion analyses. To obtain roll-over shape of the ankle-foot complex, we used trajectories of ankle and knee joints and the center of pressure(COP) between initial contact (lC) and opposite initial contact(OIC). After the roll-over shape was determined for each data, it was represented by a circular arc using the least-square method. Results showed that for the more dorsiflexed AFOs, the more distally the roll-over trajectory moved at initial contact. Also, we found that the radius of curvature significantly increased and the center of roll-over shape moved posteriorly and superiorly in dorsiflexed AFOs. Present results might provide a better understanding for the proper alignment of the orthotics as well as a single roll-over shape during walking.

The present study investigated the biomechanical effects of weight variation for side loaded carriage during walking upon joint moments and the center of body mass by using the inverse dynamic analysis. The motion data which were used as input data for inverse dynamic simulation were measured by the 3D motion analysis system. Six infrared cameras and two force plates were utilized and thirty nine reflective markers were attached to the subject to capture the walking motion with side loaded carriage. The healthy male subjects were participated in the experiment, and they walked with side loaded carriage which weighs 0, 5, 10 and 15kg, respectively. For each walking, the weight of side loaded carriage was selected randomly. As a result, the COM(Center Of Mass) was more inclined to the opposite side of side loaded carriage as the weight increased. This is the result of the balance mechanism of human in walking with side load. In other words, the human kept the total balance, leaning to the side of unloading when the human walked with one heavy side loaded. In addition, the ankle plantar-flexion moment of loading side was larger than that of unloading side when the weight increased. In knee joint, the knee extension moment of unloading side was smaller than that of loading side when the weight increased. The magnitude of hip extension moment had no significant difference. The hip extension moment of loading side was larger than that of unloading side. These results showed that the human used the ankle and hip joint of the loading side to support the body and the knee joint of the unloading side to progress the walking with keeping the balance of the body.

In this study, a multi-segment foot motion analysis on hallux valgus patients were performed using the 9-segment foot model and then compared with the results from normal subjects. Results showed that there were no significant differences in hindfoot motions between normal subjects and HV patients. However, noted in HV patients were hyper-external rotation in the talocrural joint, an excessive eversion of the subtalar joint during early stance and lack of dynamic motion in hallux MP and medial MP joints especially during terminal stance. In spite of limitation in this study due to the small number of HV patients, the current multi-segment foot model would be feasible to diagnose and treat patients with various foot diseases, combined with further studies in the future

The foot, an exceedingly complicated system, is essential to move the body forward and to keep dynamic stability during gait. In most previous studies on gait analysis, the foot has been defined as a single rigid segment, which results in many problems to understand the foot motion in detail. The purpose of this study is to develop a multi-segment foot model that can help analyze biomechanics of the foot during gait. A 9-segment foot model with 8 major joints was developed in this study. In addition, it was applied to the 3D motion analysis to determine the kinematics and the kinetics of the foot in the normal walking. Understanding the detailed foot motions by the present multi-segment foot model would be very useful to diagnose patients with various foot diseases.