Video-based Motion Analysis Research Articles

Dynamic Modeling of the Human Arm with Video-Based Experimental Analysis

The quantitative assessment of human joint torque capability has manyimportant applications. By means of a multibody approach, the authorsdescribed a formulation for 3D inverse dynamic analysis of a human armduring voluntary free movement. In particular, it is presented as a testcase where the kinematics of the arm is obtained by means of a video-based human motion analysis system.

Biomechanical Analysis of Postural Sway in Elderly Adults on Ramps

This study investigated the effects of ramp angles on postural deviation as a function of age. Five ramp inclinations (1:8, 1:10, 1:12, 1:16, and 1:20) were examined in both ascent and descent directions. Five younger (22 to 28 years) and five older (78 to 88 years) adults participated in the study. Video-based motion analysis was used to measure torso and hip angles while participants walked on an adjustable inclined ramp. Both young and older participants had a significant increase in torso angle across ramp slopes from ascent to descent. In addition, the data indicated that older participants tended to lean to the right while walking while the young participants leaned to the left. Measurements of hip angle revealed that young participants had significantly greater hip movement than older participants and that hip angle decreased significantly as participants transitioned from descent to ascent trials. Based on the data observed, it is possible that ramp descent is more problematic for elderly adults. However, within the ramp conditions evaluated, the data were unable to clearly discriminate between ramp slopes beyond identifying differences between slopes of ascent and descent.

The effect of component placement on knee kinetics after arthroplasty with an unconstrained prosthesis

The mechanical success of a total knee replacement demands stable patellar tracking without subluxation and, stable tracking, in turn, can depend largely on the medial–lateral forces restraining the patella. Patellar button medialization has been advocated as a means of reducing subluxation, and experimental evidence has shown femoral component rotation also affects medial–lateral forces. Surgeons have choices in femoral component rotation and patellar button medialization and must frequently make intra-operative decisions concerning component placement because of anatomical variations among patients. Thus, in seeking to minimize medial–lateral patellar force, we examined the effects of patellar button medialization and external femoral component rotation. The study used an unconstrained total knee system implanted in nine cadaveric specimens tested on a knee simulator operating through flexion angles up to 100°. Tests included all combinations of external femoral component rotation of 0°, 2.5°, and 5° and patellar placement at the geometric center and at 3.75 mm medial to the geometric center. A video-based motion analysis system tracked patellar and tibial kinematics while a six-component load cell measured patellofemoral loads. Repeated measures analysis of variance revealed a statistically significant decrease in the average medial–lateral force with button medialization but no significant change with femoral component rotation. Neither femoral component rotation nor patellar button medialization had an effect on the normal component of the patellar reaction force. External femoral component rotation did cause significant increases in lateral patellar tilt, in tibial varus angle, and in external tibial rotation. Button medialization caused significant increases in lateral patellar tracking, lateral patellar tilt and external tibial rotation. The results in medial–lateral patellar forces quantify the benefit of patellar button medialization and discount any benefit of femoral rotation. The change in tibial kinematics with patellar button medialization and femoral component rotation cannot be measured in vivo with current technology, and the precise clinical implications are unknown.

Throwing accuracy in the vertical direction during prism adaptation: not simply timing of ball release.

In a previous study, others have hypothesized that the variance in vertical errors that occurs while throwing at visual targets is caused by changes in any of three throw parameters: hand location in space, hand translational velocity, and hand orientation. From an analysis of skilled throwers, those authors concluded that vertical error is best correlated with variance in hand orientation, which in turn is related to the timing of ball release. We used a vertical prism adaptation paradigm to investigate which of these throwing parameters subjects use when adapting to external perturbation. Our subjects showed no correlation between hand position or hand translational velocity and ball impact height in normal, over-practiced throwing. However, video-based motion analysis showed that modifications both of position and speed of the hand play an important role when subjects are forced to compensate for a vertically shifting prism perturbation during a dart-like throw (these factors contribute approximately 30% of the adaptation). We concluded that, during adaptation, more degrees of freedom and more sources of potential error are modified to achieve the gaze-throw recalibration required to hit the target than are employed in this type of throw during normal conditions.

A Method for the Long-Term Gait Assessment Utilizing Accelerometers and Gyroscopes.

This paper describes an alternative method for the assessment of locomotion, based on the combination of the advanced wearable instruments and a simple kinematic model. The advantage of the method is that it does not require special laboratory equipments and can be used for field studies with a completely body-mounted recording system. Multiaxis accelerometers and gyroscopes were attached to each segment of lower extremities. The process included detection of temporal parameters of locomotion, calculation of joint angles, and estimation of the ground reaction force in the sagittal plane. In addition, inter segmental joint moments and powers were calculated by inverse dynamical analysis. Finally we obtained an index of energy expenditure. Validation of the method was evaluated in comparison with a conventional gait analysis system such as video-based motion analysis system and force plate. Initial results show that it is possible to use this method for the long-term assessment of locomotion during normal level walking.

Interaction of the body, head, and eyes during walking and turning.

Body, head, and eye movements were measured in five subjects during straight walking and while turning corners. The purpose was to determine how well the head and eyes followed the linear trajectory of the body in space and whether head orientation followed changes in the gravito-inertial acceleration vector (GIA). Head and body movements were measured with a video-based motion analysis system and horizontal, vertical, and torsional eye movements with video-oculography. During straight walking, there was lateral body motion at the stride frequency, which was at half the frequency of stepping. The GIA oscillated about the direction of heading, according to the acceleration and deceleration associated with heel strike and toe flexion, and the body yawed in concert with stepping. Despite the linear and rotatory motions of the head and body, the head pointed along the forward motion of the body during straight walking. The head pitch/roll component appeared to compensate for vertical and horizontal acceleration of the head rather than orienting to the tilt of the GIA or anticipating it. When turning corners, subjects walked on a 50-cm radius over two steps or on a 200-cm radius in five to seven steps. Maximum centripetal accelerations in sharp turns were ca.0.4 g, which tilted the GIA ca.21 degrees with regard to the heading. This was anticipated by a roll tilt of the head of up to 8 degrees. The eyes rolled 1-1.5 degrees and moved down into the direction of linear acceleration during the tilts of the GIA. Yaw head deviations moved smoothly through the turn, anticipating the shift in lateral body trajectory by as much as 25 degrees. The trunk did not anticipate the change in trajectory. Thus, in contrast to straight walking, the tilt axes of the head and the GIA tended to align during turns. Gaze was stable in space during the slow phases and jumped forward in saccades along the trajectory, leading it by larger angles when the angular velocity of turning was greater. The anticipatory roll head movements during turning are likely to be utilized to overcome inertial forces that would destabilize balance during turning. The data show that compensatory eye, head, and body movements stabilize gaze during straight walking, while orienting mechanisms direct the eyes, head, and body to tilts of the GIA in space during turning.

A deficient anterior cruciate ligament does not lead to quadriceps avoidance gait.

Without an intact anterior cruciate ligament (ACL) to resist anterior tibial translation, it is commonly believed that ACL-deficient patients employ alterations in walking. Although there is no consensus in the literature about the specific kinematic and kinetic adaptations in these patients with ACL tears, the gait adaptation of quadriceps avoidance is perhaps the one most popularized. The purpose of our study was to determine whether quadriceps avoidance is common in patients with ACL-deficiency. We used a video-based motion analysis system and surface electromyography (EMG) to study 18 patients with ACL-deficiency. All patients demonstrated an internal knee extension moment during early mid-stance (similar to normal subjects). Quadriceps EMG activity was noted throughout most of stance. No patients demonstrated an internal knee flexion moment, a decreased internal knee extension moment or a decreased duration of quadriceps EMG activity during stance. The findings of this study would suggest that quadriceps avoidance as a gait adaptation in ACL-deficient patients may be less common than previously reported.

Effects of walking velocity on vertical head and body movements during locomotion.

Trunk and head movements were characterized over a wide range of walking speeds to determine the relationship between stride length, stepping frequency, vertical head translation, pitch rotation of the head, and pitch trunk rotation as a function of gait velocity. Subjects (26-44 years old) walked on a linear treadmill at velocities of 0.6-2.2 m/s. The head and trunk were modeled as rigid bodies, and rotation and translation were determined using a video-based motion analysis system. At walking speeds up to 1.2 m/s there was little head pitch movement in space, and the head pitch relative to the trunk was compensatory for trunk pitch. As walking velocity increased, trunk pitch remained approximately invariant, but a significant head translation developed. This head translation induced compensatory head pitch in space, which tended to point the head at a fixed point in front of the subject that remained approximately invariant with regard to walking speed. The predominant frequency of head translation and rotation was restricted to a narrow range from 1.4 Hz at 0.6 m/s to 2.5 Hz at 2.2 m/s. Within the range of 0.8-1.8 m/s, subjects tended to increase their stride length rather than step frequency to walk faster, maintaining the predominant frequency of head movement at close to 2.0 Hz. At walking speeds above 1.2 m/s, head pitch in space was highly coherent with, and compensatory for, vertical head translation. In the range 1.2-1.8 m/s, the power spectrum of vertical head translation was the most highly tuned, and the relationship between walking speed and head and trunk movements was the most linear. We define this as an optimal range of walking velocity with regard to head-trunk coordination. The coordination of head and trunk movement was less coherent at walking velocities below 1.2 m/s and above 1.8 m/s. These results suggest that two mechanisms are utilized to maintain a stable head fixation distance over the optimal range of walking velocities. The relative contribution of each mechanism to head orientation depends on the frequency of head movement and consequently on walking velocity. From consideration of the frequency characteristics of the compensatory head pitch, we infer that compensatory head pitch movements may be produced predominantly by the angular vestibulocollic reflex (aVCR) at low walking speeds and by the linear vestibulocollic reflex (1VCR) at the higher speeds.

The motion analysis system and goniometry of the finger joints

The application of a video-based motion analysis system for goniometry of finger joints during measurement of the fingertip motion area has been assessed. The results indicate that the motion analysis system is reliable for angular measurements of finger joints that are comparable with those obtained by conventional goniometer. The advantages of using the motion analysis system is that it can record and show the changes in angle of all finger joints continuously during finger motion.

Determination of joint functional axes from noisy marker data using the finite helical axis

When video-based motion analysis systems are used to measure segmental kinematics, the finite helical displacement computed between two adjacent body segments in two successive positions i, i + 1 is often used to approximate the instantaneous joint movement. The measured trajectories of the external markers glued on the skin are very perturbed compared to the real displacement of the bony structure, and the inaccuracy in the measurement leads to stochastic errors in the position and direction of the finite helical axis of motion (FHA). As the errors associated with the FHA estimates are inversely proportional to the rotaion magnitude (Woltring, H.J., Huiskes, R., de Lange, A., 1983. Measurement error influence on helical axis accuracy in the description of 3D finite joint movement in biomechanics. In: Woo, S.L., Mates, R.E. (Eds.), Biomechanics symposium AMD 56 (FED 1), New York ASME, pp. 19–22), it is illusive to expect to assess the helical displacement between two neighbouring positions, and so to describe the joint evolution using FHA theory in such a context. A quantification of the errors on the FHA parameters computed between two successive positions i, i + 1 is proposed in this paper, using a numerical simulation of the knee joint evolution during gait. This case has been chosen because previous studies (Cappozzo, A., Catani, F., Leardini, A., 1993. Skin movement artifacts in human movement photogrammetry. Proceedings of the 14th Congress of the International Society of Biomechanics. Paris, France, pp. 238–239) have experimentally described skin and soft tissues perturbations. The results obtained from this simulation lead to two conclusions: first, they confirm the relative FHA cannot be used to represent accurately the joint kinematics during a given movement; and second, they allow a prediction of the minimum joint displacement required in order to have a reliable determination of the helical axis. The aim of this paper is not to present a new calculation method for the FHA, but to propose an alternative use of the FHA. It is generally assumed to describe a joint displacement using a sequence of rotations about three successive axes. In this case, the difficulty for clinical applications is to correctly locate these axes, in order that they coincide with the functional axes of the considered joint. If the FHA theory is used to determine the location and orientation of these functional axes from corresponding pure movement recording, then the results can be very accurate provided that the measured displacement between the two finite positions i and j be sufficient with respect to the perturbing noise. One consequence of this remark is that the rotation axis of the considered, joint may remain stable in the range of motion between these positions. An example of this altenative use of the FHA is displayed in this paper which concerns the determination of the flexion/extension axis of the elbow joint. The elbow joint has been chosen for two reasons: first, it deals with a stable joint rotation axis and second, experimental data were available on a fleshless upper-limb on which the flexion/extension axis of the elbow was marked by an anatomy specialist.

Three-dimensional motion analysis of the voluntary elbow movement in subjects with spasticity.

The purpose of this study was to quantitatively compare the difference in voluntary upper extremity movements between subjects with and without spasticity. Eight normal subjects (mean 26.7 +/- 2.8 years, four males and four females) and seven subjects with spasticity (mean 25.9 +/- 4.3 years, three males and four females) were involved in this study. The subjects sat in an adjustable chair and performed two voluntary tasks involving the elbow joint. Task A was to move the hand between two touch-plates which were mounted 28 cm apart on the surface of the table. Task B was to flex and extend the elbow joint in the sagittal plane with the forearm in neutral position. Reflective markers were attached on the shoulder, the elbow and the wrist. A Peak5 video-based motion analysis system was used to record the positions of the markers in the three-dimensional (3-D) space during the movement tasks. A set of quantitative parameters were used to document the elbow movement. The results revealed that in comparison to normal subjects, subjects with spasticity exhibited a higher average jerk, a larger standard deviation of the coordinates of the markers along the movement path, a larger standard deviation of the angle between the plane of the elbow joint and the horizontal plane, and a longer 3-D path length. The characteristics of spastic elbow movement and the usage of quantitative parameters were discussed.

Inverse dynamics as a tool for motion analysis: arm tracking movements in cerebellar patients

Kinematic analysis of limb movements can be used to evaluate motion of patients with movement disorders. Those with clinically mild to moderate impairment, however, often show only small, insignificant deviations in the measured trajectories compared to those of healthy controls. Furthermore, kinematic data alone do not give sufficient information about internal quantities such as muscle activation or joint moments. In order to improve the sensitivity of motion analysis of limb movements, we propose the use of inverse dynamics, since it allows biomechanical quantities to be determined without restricting movement. We developed an inverse dynamic model of the upper limb with 9 degrees of freedom. Spatial positions (Cartesian coordinates) of anatomical landmarks, which were recorded by an infrared video-based three-dimensional motion analysis system, are transformed into body-related Cardan angles. The model determines joint moments and powers at the shoulder, elbow, and wrist. Arm tracking movements in a patient with a mild cerebellar ataxia and a healthy control demonstrate that the model allows a clear differentiation between normal and abnormal limb movements, even if no significant differences are noted in the recorded trajectories. We conlude that inverse dynamic modeling can be an effective tool for motion analysis in patients with cerebellar disorders. It also gives further insight into the parameters that may be controlled by the central nervous system.

Nonlinear Dynamic Stability of Normal and Arthritic Greyhounds

In this paper the dynamic stability of greyhound gait was analyzed within the framework of nonlinear dynamics theory. A video based motion analysis system was utilized to obtain the kinematic data of the hindlimb joints of greyhounds at trot. Phase plane portraits and first return maps for the coxofemoral, femorotibial, and the tarsal joints were calculated from averaged kinematic data for each dog. The analysis was based on the assumption that the steady state dog locomotion could be represented as a nonlinear periodic system. Using the Floquet theory, the dynamic stability of gait was quantified by computing the characteristic multipliers from experimental data. A stability index based on multipliers was used for comparison between normal and arthritic dogs. Phase plane portraits and first return maps of the dogs with transient synovitis were compared with the averaged portraits of the normal dogs. It was observed that the coxofemoral angle exhibited the maximum difference while the femorotibial and the tarsal joints showed little or no difference from those of the normals. Comparison of the Floquet multipliers indicated that the dogs with synovitis had a less stable gait than that of the normal dogs.

Abnormal tactile experience early in life disrupts active touch

The importance of early tactile experience in the development of discriminative somatomotor function was assessed by examining the proficiency and movement strategies of rats raised without normal sensory inputs provided by their mystacial vibrissae. Infant-trimmed animals had their whiskers clipped daily from birth to 45 d of age, after which they were allowed to regrow for 60-70 d before initiation of behavioral training, which lasted as long as several months. Adult-trimmed animals had their whiskers trimmed for comparable periods during adulthood. Rats were tested on one of two tactile discriminations, rough versus smooth or rough versus rough, that differed with respect to the overall size of their surface features. Whisker movements during task performance were examined in detail using video-based motion analysis software. Infant-trimmed animals performed rough versus smooth discriminations as well as adult-trimmed rats or normally reared animals. Except for one subject, infant-trimmed rats were severely impaired in their ability to distinguish rough versus rough surfaces. Deficits persisted in spite of months of training with the regrown vibrissae. The animals that failed to master this task displayed whisking patterns that notably lacked frequencies in the normal range of 6-12 Hz. Thus, abnormal tactile experience early in life substantially, and perhaps permanently, impairs sensorimotor integration underlying active touch.

A solidification procedure to facilitate kinematic analyses based on video system data

When video-based motion analysis systems are used to measure segmental kinematics, the major source of error is the displacement of skin-fixed markers relative to the underlying skeletal structure. Such displacements cause the marker representation of the segment to deform, thereby decreasing the accuracy of subsequent three-dimensional kinematic calculations. We have developed a two-step solidification procedure to address this problem. First, the mean rigid shape is computed which best represents the time-varying marker configuration of each segment. Second, a least-squares minimization is used to replace the measured marker coordinates with those corresponding to the best-fit mean rigid shape. Rigid body theory can then be applied unambiguously to perform kinematic analyses. To evaluate this approach, we defined an unperturbed three-dimensional reference movement using kinematic data from the swing phase of gait. After perturbing the marker coordinates with artificial noise, the rotation matrix and translation vector (absolute and relative movement) between each pair of successive images were computed using (1) reference frames fixed directly to the perturbed marker coordinates, (2) a least-squares minimization procedure found in the literature, and (3) the proposed solidification procedure. The least-squares and solidification procedures produced extremely similar results which, relative to the direct calculation, reduced kinematic errors on average by 20–25% when the maximum distance between markers was small (e.g. < 15 cm). The solidification methodology therefore combines the numerical benefits of the least-squares method with the conceptual benefits of a rigid body method.

Effect of an abdominal binder during wheelchair exercise

The purpose of this study was to determine whether use of an abdominal binder would affect oxygen uptake, trunk range of motion, and duration of the stroke phase during wheelchair propulsion. The subjects were six paraplegic wheelchair athletes with T1-T6 injuries and no abdominal muscle function. Each subject performed two trials, one while wearing the binder and one without the binder. Each trial consisted of submaximal and maximal exercise tests conducted on wheelchair rollers. Oxygen uptake was determined by open circuit spirometry while heart rate was determined by telemetry. Max VO2 values averaged 2.51 l.min-1 while average maximum heart rate values were 190 b.min-1. A 3-D video-based motion analysis system was used to obtain kinematic parameters of wheelchair propulsion. In general, 30% of the cycle time was comprised of the stroke phase, while 70% was comprised of the recovery phase across speeds. There were no statistically significant effects of the abdominal binder on any of the cardiovascular or kinematic variables at submaximal or maximal levels of exercise. Under the conditions of this laboratory investigation, it appears that an abdominal binder does not alter physiological or selected biomechanical measures in highly trained athletes.

Correlation between physical activity and the gait characteristics and ankle joint flexibility of the elderly

The correlation between the type, duration and intensity of physical activity on the gait characteristics and the range of active ankle joint motion of the elderly were investigated in this study. Three-dimensional (3D) kinetic and kinematic assessments were performed on the normal walking patterns of 59 healthy elderly male and female subjects (aged 60–79 years). Gait analysis was performed using a high-speed video-based (3D) motion analysis system with synchronized ground-reaction force measurements. The maximal active range of motion (RoM) of the ankle joint complex of each subject was determined using an external six-degree-of-freedom flexibility assessment device. Physical activity levels were classified based on energy expenditure requirements. In general the results suggest that habitual level of physical activity did not have a significant effect on the kinetic or kinematic variables during walking, or the maximal ankle joint range of motion. Differences in ankle joint RoM and gait variables were found based on gender. No distinct benefit with respect to ankle joint range of motion or gait characteristics was provided with participation in higher-energy intensive physical activities in comparison to physical activities requiring low to moderate energy expenditures. It is speculated that the benefits of physical activity may be more pronounced in activities which demand rapid muscular strength and control movements such as recovering from a fall or obstacle avoidance.

Evaluation of lens distortion for video-based motion analysis

Evaluation of lens distortion for video-based motion analysis

Aging, vertebral density, and disc degeneration alter the tensile stress-strain characteristics of the human anterior longitudinal ligament.

The mechanical properties of the human lumbar anterior longitudinal ligament were investigated, and the influence of aging, disc degeneration, and vertebral bone density on these properties was determined. Tensile mechanical properties of the vertebra-anterior longitudinal ligament-vertebra complex were determined for 16 segments from cadavera of individuals who had been 21-79 years old (mean, 52.1 years) at the time of death. Regional strain patterns associated with three sites across the width and three sites along the length of the anterior longitudinal ligament were measured with use of a video-based motion analysis system. In the young, normal anterior longitudinal ligament, the elastic moduli of the insertion and substance regions of the ligament were similar (approximately 500 MPa). During aging (21-79 years), the elastic modulus of the substance region increased 2-fold, whereas the elastic modulus of the insertion decreased 3-fold; this resulted in an approximately 5-fold difference in elastic modulus between these regions in the older spine. The strength of the bone-ligament complex decreased approximately 2-fold (from 29 to 13 MPa) over this same age range. The outer portion of the anterior longitudinal ligament consistently had the highest peak tensile strains (11.8 +/- 2.7%) in all of the specimens examined. Preparations with nondegenerated discs and high bone density were significantly stronger (66%) and failed in the ligament substance; in contrast, segments from older individuals with degenerated discs and lower bone density failed in the ligament insertion regions.

Elbow joint restriction: Effect on functional upper limb motion during performance of three feeding activities

This study was conducted to quantify and compare changes in upper limb joint motion during different feeding tasks when the elbow joint was restricted. Ten male and nine female volunteer subjects age 18 to 50 years participated; all were healthy, right dominant, with no upper limb pathology. A splint was used to restrict elbow joint motion. Three feeding tasks under both unrestricted and restricted conditions were randomly assigned; motion was recorded by a video-based three-dimensional motion analysis system. Elbow restriction resulted in significantly (p < .05) larger arcs of motion in shoulder flexion and internal rotation. Differences between feeding types were similar during both unrestricted and restricted conditions. Increased shoulder joint motion resulting from elbow joint restriction may require greater activity of shoulder girdle muscles increasing the risk of soft tissue problems and degenerative joint disease. Decisions regarding elbow immobilization should take into consideration potential effects upon total upper limb motion.