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Slips and falls often occur in the industrial environments. They are not only caused by environmental hazards but also by some biomechanical factors related to deficient ability of postural control to arrest impending falls. The purpose of this study is to simulate the slip condition in human walking and to find out the possible related factors of biomechanics.

Eleven male and 9 female recruited were healthful without any musculoskeletal and neurological impairments. In order to provide different disturbance level, three lean angles of tilting boards were designed as 10, 20, 30 degrees with respect to horizontal plane. Subjects wore a safety harness, stood on the tilting board and were released without awareness. A forceplate applied a soap patch was in front of the tilting board to serve the slippery perturbation and to measure the fool/floor reactions. Movements of body segments were measured using the motion analysis system.

The results were shown that lean angle had a significant effect to all parameters except step length, response time, maximum ankle forward velocity, hip forward velocity, and ankle flex angle. The gender significantly affected on the step length, response time, maximum ankle forward velocity, and knee forward velocity. Larger lean angle made subjects to take a more rapid step. In order to absorb the shock in foot strike, subjects flexed more their knee and increased the foot landing angle in larger lean angle. Male tended to adopt the long step-length strategy to respond to the slippery perturbation and female tended to use the short step-length strategy instead. The results of maximum ankle forward velocity suggested that short step-length strategy could be belter to reduce the foot slip than long step-length strategy.

This study scientifically measures the dynamic gait characteristics and energy cost of six male below-knee amputees, three vascular and three traumatic, while wearing SACH, single axis and multiple axis prosthetic feet via six-camera motion analysis, metabolic measurement cart and heavy-duty treadmill. Subjective results are additionally determined via questionnaire after testing. Motion analysis showed statistically significant differences at p < 0.05 between the solid ankle cushion heel (SACH), single axis and multiple axis foot in the velocity, cadence, stride length end gait cycle. Significant differences were found in energy cost among the prosthetic feet tested, and significant changes in walking under different speeds and different inclines. Results provide quantitative and qualitative information about the dynamic performance of the various feet which can be helpful in prescribing the optimal prosthetic foot for individual amputees.

Elbow joint loading was evaluated during a forward fall at various elbow initial flexion angles, in order to determine which is the best elbow initial flexion angles to prevent the elbow injury during a fall. Subjects were asked to perform a forward fall and followed by a push-up motion in different elbow initial flexion angles: 0°, 20°, 40° and unrestricted group. Fall on the outstretched hand is the leading cause of upper extremity injury. There are far more extension type of supra-condylar fracture of the elbow than flexion type. Flexion of the elbow may represent the effects of damper and spring. Using the motion analysis system, the kinematics and kinetics of the elbow joint were investigated under various elbow initial flexion angles. The loading biomechanics of the elbow joint differed with various elbow initial flexion angles. The ground reaction forces decrease with increase of elbow flexion upon impact. Different initial elbow flexion angles would affect the biomechanics of upper extremities during falls. Forward fall with elbow in extension is more dangerous. Knowledge of elbow kinematics and kinetics may be helpful in preventing injuries by reducing the ground reaction force with changes of the elbow initial flexion angles during a fall.

The purposes of the present study were to (1) investigate the effects of the arm movement and initial knee joint angle employed in standing long jump by the ground reaction force analysis and three-dimensional motion analysis; and (2) investigate how the jump performance of the female gender related to the body configuration. Thirty-four healthy adult females performed standing long jump on a force platform with full effort. Body segment and joint angles were analyzed by three-dimensional motion analysis system. Using kinetic and kinematic data, the trajectories on mass center of body, knee joint angle, magnitude of peak takeoff force, and impulse generation in preparing phase were calculated. Average standing long jump performances with free arm motion were +1.5 times above performance with restricted arm motion in both knee initial angles. The performances with knee 90° initial flexion were +1.2 times above performance with knee 45° initial flexion in free and restricted arm motions. Judging by trajectories of the center mass of body (COM), free arm motion improves jump distance by anterior displacement of the COM in starting position. The takeoff velocity with 90° knee initial angle was as much as 11% higher than in with 45° knee initial angle. However, the takeoff angles on the COM trajectory showed no significant differences between each other. It was found that starting jump from 90° bend knee relatively extended the time that the force is applied by the leg muscles. To compare the body configurations and the jumping scores, there were no significant correlations between jump scores and anthropometry data. The greater muscle mass or longer leg did not correlated well with the superior jumping performance.

The wrist and thumb postures adopted during the use of three different types of computer mouse (mini mouse; standard mouse; MouseMan) to perform eight standardized tasks were evaluated. Thirty elementary students between seven to twelve years of age were studied using a magnetic tracking system. The peak value and angular range of motion of the wrist and thumb extension/flexion and radial/ulnar deviation were measured during performing 8 standard tasks. There were statistically significant larger values in the standard mice with regard to extreme wrist extension. Angular range of wrist extension observed for the standard mice were also much higher than the mini mouse and MouseMan. There were statistically significant larger values in the MouseMan with regard to extreme wrist ulnar deviation, and an average decrease in extreme thumb flexion and angular range of thumb flexion. The results from the questionnaire showed that most elementary students preferred to use the standard mouse (40%) next was the MouseMan (37%); and the last the mini mouse (23%). The recommendation of mouse types based on the hand length for elementary students was not statistically significant in our study.

Recently, there are more people jogging with a treadmill at the gym or the home setting. The main available selected modes for treadmill jogging are speed and slope of incline. Increased speeds and incline slopes will not only increase the cardiopulmonary loading but may also alter the lower extremity (LE) movement patterns. There are few systematic investigations of the effect of the speed and incline on LE kinematics. Most studies have used 2D methods which focused on movements in sagittal plane only and this has limitations in the acquired data since lower extremity movements also include frontal and transverse planes. The current study aimed to investigate LE movement during jogging at different speeds and incline slopes using a high speed three-dimensional (3D) motion analysis system.

Eighteen young healthy males were recruited. The video-based motion capture system with six CCD cameras, HIRES Expert Vision System (Motion Analysis Corporation, CA, USA), was used to collect kinematic data at a sampling frequency of 120Hz. Nineteen passive reflective markers were attached to bilateral lower extremities of the subject. The joint angle is calculated by Euler angle using the rotation sequence: 2-1-3 (y-x′-z″). Four speeds were selected: 2 m/s, 2.5 m/s, 3 m/s, 3.5 m/s with the slope at 0, and four slopes were selected: 0%, 5%,10%,15% at a speed of 3 m/s. Repeated-measures ANOVA was used to test hypotheses regarding changes in jogging condition on LE kinematic variables. The significance level was set at 0.05.

As the jogging slope increased, the hip, knee and ankle demonstrated a significantly greater maximum flexion in swing phase (p<0.001), but the maximum extension angles in stance phase were relatively unchanged. Increased LE flexion during swing phase is important to ensure foot clearance with increased slope. For increased speed, the hip and ankle joints had significantly greater maximum joint extension angles during stance phase and the hip and knee joint had significantly larger maximum flexion angles in swing phase (p<0.001). Increased motion during swing phase account for a larger step length and increased motion during stance phase may facilitate the generation of power during forward propulsion as the jogging speed increased. As the slope and speed increased, LE movement patterns were changed in the transverse plane: the significantly increased (p<0.01) internal hip rotation at terminal stance, the increased toe-in of foot (p<0.001) during terminal stance phase and decreased (p<0.05) toe-out during swing phase. Increased hip motion in transverse plane could lengthen the stride distance and increase foot toe-in for providing a stable lever for push off to increase propulsion force as speed or slope is increased. By way of systematic 3D kinematic investigation of the LE in jogging, the results further elucidate the effect of changing speed and incline on LE joints movements. This information could provide guidelines for rehabilitation clinicians or coaches to select an appropriate training mode for jogging.

Flexion of the index finger is a fairly complex process requiring the coordination of different joints. This study is the first attempt to investigate how the angular velocity profile of the three right index joints (DIP, PIP, and MCP) varies with respect to time during the course of flexion. Ten right-handed subjects (healthy college students between 21 and 23 years old) were recruited to participate in the experiment. Each of these human subjects was instructed to perform a flexion task with his/her right hand. Five miniaturized (5-mm diameter) reflective markers were applied to each human subject: three placed at the DIP, PIP, and MCP joints of the index finger on the side close to thumb, and the rest at the predetermined landmarks on dorsum of thumb. A high-speed camera was used to record the motion of the index finger during a paced flexion, and the instantaneous angular velocity of each joint was determined by relating the marker displacement to the frame frequency (~5 ms between two consecutive frames). Opposite to the general belief that the speed is constant throughout a flexion cycle, to our best knowledge, this study, for the first time, has revealed that the speed of multi-joint movement actually varies with time. It has been identified that during one full flexion cycle, the angular velocity of the three joints of interest undergoes five distinguishable phases, referred as phases P1 (slow), P2 (fast), P3 (slow), P4 (fast), and P5 (slow), respectively. It has also been observed that duration of each of phases P1, P2, P4, or P5 accounts for approximately 10–15% of the whole flexion cycle, while P3 lasts for nearly half a cycle. Furthermore, although the flexions of DIP, PIP, and MCP joints cycle through the same five phases, the starts of their respective phases tend to vary. In P2 and P5, flexion of MCP takes place considerably later than those of PIP and DIP, whereas DIP flexes earlier than PIP in P2. The angular velocity of each joint reaches its peaks in P2 and P4; the peak velocity of DIP occurs earlier than that of PIP or MCP in P2, whereas peak of MCP is reached later than that of PIP. Moreover, the three joints of index finger flex with different angular velocities in each of the five phases: PIP moves significantly faster than MCP in P2, whereas DIP moves faster than MCP in P4. The results from our study indicate that the multi-joint motion of index finger is an uneven course, i.e. different joints flex with different angular velocities during the flexion. The temporal features of the velocity due to a single joint or multi-joint motion provide useful information to further clarify the dexterity of finger movement.

Total Knee Arthroplasty (TKA) using standard artificial knee implant has a limitation in restriction in the range of motion and freedom of movements'. This study was worked out to compare the kinematics of a reconstructed 3D knee with standard and high flexion artificial knee designs. A CT bone model reconstructed with MIMICS for a 3D normal knee joint and the simulation was done for normal knee, standard version of artificial knee as well as the high flexion knee designs. The results of the analyses, provides us an insight that high flexion designs were most suited and gives increased range of motion and also provides an additional degree of freedom so that it almost mimics the normal knee movement.

The high flexion design when tested under simulated environment provided a better functionality and increased movements. It was concluded that the normal knee has 6 degrees of freedom (DOF); the standard version has 1 rotation and 1 translation. The high flexion design provides 2 rotations and 1 translation.

Measurement of the three-dimensional (3D) motions and surface kinematics of total knee replacements (TKR) during different kinetic activities helps provide necessary knowledge for a better use of these activities for rehabilitation purposes. The 3D kinematics of the knee in eight patients with posterior cruciate ligament-retaining (PCL-retaining) mobile-bearing TKR were measured during sit-to-stand, a closed kinetic chain (CKC) activity, and active knee flexion/extension, an open kinetic chain (OKC) activity, using a single-plane, 3D fluoroscopy method. Angular, translational motions as well as the contact patterns of the prosthesis components were calculated. The joint angular motion patterns were not statistically different between the OKC and CKC activities, but different contact patterns were found. The knee joint center translated more anteriorly during OKC than during CKC activities. Compared to the CKC activity, the more anterior contact positions and smaller total displacements of the medial contact in the OKC activity may indicate a greater loading in PCL and a smaller contact area on the medial tibial plateau. Rehabilitation of patients with mobile-bearing TKR may have to consider the potential negative effects of the greater loadings in the PCL and greater stresses in the medial tibial plateau when using OKC as a training exercise.

Few studies have concurrently investigated the accuracy and repeatability of an optical and electromagnetic (EM) system during dynamic motion. The purposes of this study were to: (1) assess the accuracy of both an EM and optical system when compared to a gold standard and (2) to compare the intra- and inter-day repeatability during 3D kinematic motion of both systems. The gold standard used for accuracy assessment was a robot programmed to manipulate a carbon fiber beam through pre-defined motions within the capture volume of both systems at 30, 45 and 60°/s. A total of 12 healthy young adults were tested for intra- and inter-day repeatability of hip, knee and ankle joint angles during a sit-to-stand movement. Marker trajectories were captured using an 8-camera Motion Analysis system and a Polhemus Liberty system. Optical markers for both portions of the study were precisely marked to allow for digitization by the EM system, with collections taken at 120 Hz. Accuracy and repeatability were assessed using the RMS error and coefficient of multiple correlations (CMC), respectively. The optical system demonstrated a 1–2.5° lower RMS error in tracking the robot movements in the transverse and sagittal planes when compared to the EM system. However, it was possible that metal interference affected the accuracy of the EM system. High intra-day and inter-day repeatability was demonstrated by both systems during the sit-to-stand task. The optical system did demonstrate slightly higher CMC values for between day trials, though skin motion artifact might have affected the EM system to a greater extent. Overall, both systems demonstrated an adequate ability to track dynamic motion.

Back pain can affect up to 65% of the American population and cost the health care system approximately fifty billion dollars each year. Due to the difficulty with recording spine/trunk movement, several methods and models exist. The myriad of methods and the need for understanding of spine/trunk motion has led to a lack in a ‘gold-standard’ of treatment for individuals with back pain. Therefore, the purpose of this study was to examine the effect of different activities of daily living on the kinematics of individual trunk segments in young adults to determine how common ambulatory tasks will alter trunk motion compared to level walking.

Young healthy adults completed, in a random order, four activities of daily living: level walking, obstacle crossing, stair ascent and descent using a previously validated model. Subjects were outfitted with a full body marker set which included a segmented trunk. Multi-segmented trunk angles between the three inferior segments, sacrum to lower lumbar [SLL], lower lumbar to upper lumbar [LLUL] and upper lumbar to lower thorax [ULLT], were calculated and compared between tasks. Peak flexion angles, instance of peak angle and range of motion were analyzed.

The overall hypothesis that different spine levels will have altered kinematics during various activities of daily living was supported. Stair descent had smaller peak flexion angles than obstacle crossing and stair ascent. The instance of peak angle were different depending on trunk angle and daily task. The most inferior trunk angle — Sacrum-to-Lower Lumbar — had the largest range of motion during all four tasks in all three (sagittal, frontal and transverse) planes of motion.

This study was able to show how various activities of daily living produce different motions in the three inferior segments of a multi-segmented trunk method. The results of this study are the first steps in understanding how the trunk responds on a daily basis and how those responses could lead to back pain.

The passive extensibility of skeletal muscles is an important health-related component of physical fitness. Tight gastrocnemius is a common orthopedic problem and frequently leads to overuse injuries of the lower extremity. Moreover, gastrocnemius tightness is commonly associated with lower back pain. Previous studies have reported that tight gastrocnemius results in kinematic and kinetic deviations of the ankle and knee during gait and a greater hip flexion at the moment of maximal ankle dorsiflexion. Accordingly, this study performs an experimental investigation into the effects of tight gastrocnemius on the hip and pelvic movements in gait. Sixteen subjects with tight gastrocnemius (defined as $<10^{\circ }$ of ankle dorsiflexion with knee extended) and 16 healthy individuals matched by age and gender participated in the study. The three-dimensional angles of the hip and pelvis and moments of the hip were obtained for both groups during the stance phase of gait using force plates and a motion analysis system. Compared with the control group, the peak hip flexion angle is significantly higher in the tight group ($p=0.001$), while the peak hip extension angle is significantly lower ($p=0.001$). Moreover, the peak pelvic anterior tilt is significantly higher than that of the control group ($p=0.001$), while the peak pelvic posterior tilt is significantly lower ($p=0.001$). Finally, the peak extensor moment of the tight group is significantly higher than that of the control group ($p=0.049$), while the peak flexor moment is significantly lower ($p=0.003$). The results confirm that tight gastrocnemius leads to changes in the three-dimensional hip and pelvic angles and hip moments during gait. Disturbance of the hip and pelvic movement is thus a critical clinical consideration when evaluating soft tissue injuries in patients with tight gastrocnemius.