COM Displacement Research Articles

Mobility Assessments

While many organizations have adopted various forms of movement screens, designers of these assessment tools fail to understand the difference between skill and mobility. Numerous studies within the motor control and learning literature demonstrate how proper verbal instructions and demonstration enhance skill acquisition. The cumulative result of these studies reinforces the importance for movement screens to include instructional descriptions of test-items in a manner in which the results isolate skill from mobility. PURPOSE: To compare performance on a common movement screen with limited instructions and with instructions including verbal instruction, demonstration, and practice. METHODS: 22 individuals (14 males, 8 females; 22 ± 1.4 years) participated. Each participant performed three overhead squats under three different conditions: baseline with no instruction, instructions taken from the Functional Movement Screen (FMS), and instructions including demonstration, and practice (IDP). Whole body kinematics were recorded using a 12-camera motion capture system. Center of mass vertical displacement, ankle flexion, trunk forward lean, and bar to body distance were extracted. Differences between conditions were assessed using a one-way ANOVA. RESULTS: COM displacement was greater in IDP (0.45 ± 0.10m.) than FMS condition (0.32 ± 0.20m.; p = 0.003), but not different than baseline (0.39 ± 0.12m.; p = 0.047). Forward trunk lean was also greater in IDP (0.33 ± 0.65m.) than FMS condition (0.29 ± .096m.; p =0.013) but not different than baseline (0.30 ± 0.07m., p = 0.048). Ankle dorsiflexion was greater in IDP (21.33° ± 5.22) than FMS condition (17.62° ± 6.26; p = 0.01) but not different than baseline (20.94° ± 4.7; p = 0.035). Bar to body distance was not different between any conditions. CONCLUSION: The results of this study suggest that practitioners using movement screens to identify movement dysfunction strongly consider whether they are seeing actual dysfunction or a lack of movement skill.

배구경기 세터 토스 동작의 운동학적 비교분석

Purpose : The purpose of this study was to analyze setter toss motion kinematically according to toss types. Method : Dependent variables were elapsed time, vertical displacement of the body center, the projected speed of the ball, and differences of the joint angle to the target for four setters positioning. Result : There was no significant difference in the time but the ball contact time was shorter when the toss distance of P3 was longer. There was significant difference in the vertical displacement of COM (p<.05). The vertical displacement of COM showed that the vertical movement gradually decreased when the quick distance was longer. The vertical displacement of COM was difference (p<.05), also there was difference of the ball speed (p<.001) at the Release point(E4). There was significant difference in the knee joint angle at a certain moment among the Release(E4) and Landing point(E5)(p<.05). The hip joint was significant difference among the Apex(E2), Ball Touch(E3), Release(E4), and the Landing point(E5) on the surface(E2, E3, E4 p<.05; E5 p<.005). The shoulder angle was significant difference among the Ball Touch(E3), Release(E4) and the Landing point(E5) on the surface(E3, E4 p<.05; E5 p<.001). The elbow was significant difference in the Apex(E2) (p<.05). The wrist was significant difference in the Release(E4) (p<.05). Conclusion : If we find the clue to expect the direction of the setter’s ball, we have to fine the clues in the Apex(E2) that hip join and elbow, Ball Touch(E3) that hip joint and shoulder joint, Release(E4) that wrist, elbow, hip joint, and knee joint.

드롭랜딩 시 착지형태에 따른 충격흡수구간의 운동역학적 특성

Objective : The purpose of this study was to investigate the biomechanical properties of shock absorption strategy and postural stability during the drop landing for each types. Methods : The motions were captured with Vicon Motion Capture System, with the fourteen infra-red cameras (100Hz) and synchronized with GRF(ground reaction force) data(1000Hz). Ten male soccer players performed a drop landing with single-leg and bi-legs on the 30cm height box. Dependent variables were the CoM trajectory and the Joint Moment. Statistical computations were performed using the paired t-test and ANOVA with Turkey HSD as post-hoc. Results : The dominant leg was confirmed to show a significant difference between the left leg and right leg as the inverted pendulum model during Drop Landing(Phase 1 & Phase 2). One-leg drop landing type had the higher CoM displacement, the peak of joint moment with the shock absorption than Bi-leg landing type. As a lower extremity joint kinetics analysis, the knee joint showed a function of shock absorption in the anterior-posterior, and the hip joint showed a function of the stability and shock absorption in the medial-lateral directions. Conclusion : These findings indicate that the instant equilibrium of posture balance(phase 1) was assessed by the passive phase as Class 1 leverage on the effect of the stability of shock absorption(phase 2) assessed by the active phase on the effect of Class 2 leverage. Application : This study shows that the cause of musculo-skeletal injuries estimated to be focused on the passive phase of landing and this findings could help the prevention of lower damage from loads involving landing related to the game of sports.

Effects of a light touch on fixed or mobile supports on gait parameters in visually restricted young adults

We investigated the effects of lightly touching fixed and mobile supports on gait parameters and center of mass oscillations in visually restricted young adults. Fourteen healthy male and female adults of mean=23.6 years (SD=1.6 years). Twelve walking conditions were completed on the GAITRite measurement system, resulting from crossing 3 conditions of visual restriction (no restriction, partial restriction, blindfolded) and 4 conditions of haptic supplementation (no supplementation, with a cane used as “light touch”, with a cane sliding on the ground, while touching a soft elastic handrail). Gait speed, stance time, step length and the basis of support were measured. Accelerations of center of mass were also recorded through an accelerometer and the displacements of center of mass were analyzed. Results showed that visual restriction decreased in gait speed, reduced step length, while it increased the base of support and the amplitude of CoM displacements. In the full restriction condition, haptic supplementation provided by the use of the classic cane improved normalized stance time (%). In addition, in the no vision condition, both the classic cane and the soft handrail increased step length and reduced medio-lateral oscillations of the CoM. These results suggest that in visually restricted healthy adults, lightly touching a fixed (soft handrail) or a mobile (classic cane) support contributes to adaptation of gait parameters and postural control during locomotion.

컴퓨터 디자인 기반 모노스키 버킷 사용에 따른 장애인 알파인 스키 선수의 운동학적 특성 변화 연구: 사례 연구

ssistive Technology Service Center of Seoul, Republic of KoreaReceived 15 November 2014 Received in revised form 3 December 2014 Accepted 10 December 2014 ABSTRACT The purpose of the study was to investigate the effect of CAD (Computer Aided Design) based alpine mono-ski bucketdesign on disabled ski athletes’ kinematic characteristics. Two national team ski athletes with LW11 disabilities (Loco-motion Winter Classification) category for sit ski participated in both pre and post experiment. Both of the subjects per-formed 3 trials of carved turn on a ski slope under two conditions. Where, subject “A” performed pre experiment withpersonal bucket and post experiment with the newly developed CAD based bucket whereas, Subject “B” as control subjectperformed both pre and post experiment with his personal bucket. For the experiment, 24 Infrared cameras were positionedon the ski slope which covered the path of the ski turn. Also, motion capture suit with reflective markers were worn byboth subjects. In the result, decrement in medial/lateral displacement of COM, anterior/posterior displacement of COM,flexion/extension angle of trunk as well as velocity losing rate of COM was observed in subject “A” when using the newlydeveloped CAD based bucket. In contrast, no larger effect on performance was observed when using personal buckets. Inconclusion, the findings obtained from the study indicated effectiveness of newly developed CAD based bucket by reducingexcessive movement of hip and trunk which is an important factor to perform an effective turn. Keywords :

정상인에서 유도된 첨족에 따른 신체 보행의 특성

The purposes of this study was to investigate the physical compensation for gait on induced equinus in normal subjects. Ten subjects were participate in the experiment (age: 23.8±2.8 yrs, height: 177.3±4.3 cm, weight: 70.8±4.6 kg). The study method adopted 3D analysis with six cameras and ground reaction force with two force-plate. Induced equinus were classify as gait pattern on unilateral and bilateral equinus. The results were as follows; In displacement of COM, medio-lateral and anterior-posterior COM were no significant, but in vertical COM, unilateral equinus gait was higher than bilateral equinus gait. In displacement hip joint, left hip joint was more extended in FC1 and FC2 during unilateral equinus gait. In displacement knee joint, left knee joint was more extended in FC2, right knee joint was more extended in all event during unilateral equinus gait. In trunk tilt, unilateral equinus gait was more forward tilt in TO1 and TO2. ROM of each joint was no significant. In Displacement of pelvic tilt angle, X axis of unilateral equinus gait was more increase than bilateral equinus gait at FC2, TO2 and MS2. Y axis of unilateral equinus gait was more increase than bilateral equinus gait at MS1, FC2 and MS2. Z axis was no significant in both equinus gait. In GRF, right Fx and Fy were no significant in both equinus gait, Fz was more bigger vertical force in bilateral equinus gait. Left Fx was more bigger internal force in unilateral equinus gait, Fy and Fz were no significant in both equinus gait.

Estabilidade da marcha de adultos em diferentes condições visuais: estudo piloto

The visual system is fundamental for the control of gait stability. Visual deprivation or impairment can deteriorate walking stability in adults; however, in daily life, adults are exposed to different light intensities rather than visual deprivation. The objective of this study was to investigate gait stability in young adults exposed to different visual conditions. Ten adults without visual problems participated in the study. The subjects walked at two speeds (self-selected and 30% faster) under four visual conditions: normal vision and using three different masks covered with automotive film to reduce the passage of light to the eye (50% > 20% > 5% - lowest light passage). Stability parameters (margin of stability - MOS, center of mass separation - COMSEP, and time-to-contact - TtC) obtained by analysis of the COM displacement relative to the base of support, and spatiotemporal parameters (step length, gait velocity, and support time) were assessed. The different visual conditions did not affect gait stability or spatiotemporal parameters at the two walking speeds studied. The variations in stability between visual conditions relative to normal vision were not expressive for MOS (< 4%), COMSEP (< 7%), or TtC (< 6%) at the two walking speeds. This lack of changes in stability may have been due to maintenance of the spatiotemporal characteristics because of the strong association between these characteristics. The adults studied can control stability without changing their gait patterns under different visual conditions, and lower light intensities do not increase the risk of falls

Comparative Analysis of the Change CoM Displacement, CoM Velocity and Foot-Pressure in Draw and Takeout Curling Skills

Comparative Analysis of the Change CoM Displacement, CoM Velocity and Foot-Pressure in Draw and Takeout Curling Skills

Locomotory Diseases Influence on Body Equilibrium and Balance

The paper describes a new method of body equilibrium evaluation applied for different human subjects, the principal aim being to demonstrate to what extent any locomotory diseases could influence the body stability and equilibrium. The research refers to identify some persons with different locomotory diseases and to find both the influence on equilibrium and stability and if possible to improve them. Our research stage, synthesized in this paper, explains the body equilibrium evaluation in orthostatic posture done for different subjects, aged between 20 and 40 years. A number of 10 relevant persons were considered to be evaluated, 2 of them having some locomotory diseases. The first person presents any neuro-motor stability problems in case of long standing case. The other person has both Achilles tendons torn and operated. All subjects were tested in orthostatic posture, in 3 distinct positions, using a Kistler force plate. The experiments referred to the body mass center (COM) displacement in sagittal and lateral planes, representing an interesting characteristic for its equilibrium. It was shown that the person with diseases affecting stability presented a loss of equilibrium when standing for 10-20 seconds, i.e. higher COM displacements in both planes reported to the other tested subjects.

Effects of the type and direction of support surface perturbation on postural responses

BackgroundPostural control is organized around a task goal. The two most frequently used types of tasks for postural control research are translational (translation along the anterior-posterior axis) and rotational (rotation in sagittal plane) surface perturbations. These types of perturbations rotate the ankle joint, causing different magnitudes and directions of body sway. The purpose of this study was to investigate the effects of the type (translation vs. rotation) and direction (forward/toe up vs. backward/toe down) of the perturbation on postural responses.MethodNineteen healthy subjects were tested with four perturbations, i.e., forward and backward translation and toe up and toe down rotation. The onset latency and magnitude of muscle activations, angular changes, and COM displacements were measured. In addition, the kinematic data were divided into two phases. The initial phase reflected the balance disturbance induced by the platform movement, and the reversal phase reflected the balance reaction.ResultsThe results showed that, in the initial phase, rotational perturbation induced earlier ankle movement and faster and larger vertical COM displacement, while translational and forward/toe up perturbations induced larger head and trunk angular change and faster and larger horizontal COM displacement. In the reversal phase, balance reaction was attained by multi-joint movements. Translational and forward/toe up perturbations that induced larger upper body instability evoked faster muscle activation as well as faster and larger hip or knee joint movements.ConclusionsThese findings provide insights into an appropriate support surface perturbation for the evaluation and training of balance.

Postural responses to yaw rotation of support surface

The purposes of this study were to investigate EMG and kinematic responses to yaw rotation of a support surface. Twenty people participated in four conditions, i.e., two velocities (240°/s, 120°/s) and two amplitudes (30°, 15°). Longer latency and smaller muscle responses were induced for yaw rotation, and distal ankle and knee muscles were activated earlier than trunk and neck muscles. Joint kinematics demonstrated larger angular displacements in axial rotation. Velocity and amplitude did not affect onset latency or magnitude of muscle activation but had significant effects on joint movements and COM displacements. Preliminary information about normative data of healthy subjects was obtained, and questions were generated about optimal velocity and amplitude test protocols that require further investigation.

Effect of high-heeled shoes on three-dimensional body CoM displacement during walking

Mobility limitations and cognitive impairments, each common with aging, reduce levels of physical and mental activity, are prognostic of future adverse health events, and are associated with an increased fall risk. The purpose of this study was to examine whether divided attention during walking at a constant speed would decrease locomotor rhythm, stability, and cognitive performance. Young healthy participants (n = 20) performed a visuo-spatial cognitive task in sitting and while treadmill walking at 2 speeds (0.7 and 1.0 m/s).Treadmill speed had a significant effect on temporal gait variables and ML-COP excursion. Cognitive load did not have a significant effect on average temporal gait variables or COP excursion, but variation of gait variables increased during dual-task walking. ML and AP trunk motion was found to decrease during dual-task walking. There was a significant decrease in cognitive performance (success rate, response time and movement time) while walking, but no effect due to treadmill speed. In conclusion walking speed is an important variable to be controlled in studies that are designed to examine effects of concurrent cognitive tasks on locomotor rhythm, pacing and stability. Divided attention during walking at a constant speed did result in decreased performance of a visuo-spatial cognitive task and an increased variability in locomotor rhythm.

Gait Pattern in Inherited Cerebellar Ataxias

Our aim was to perform a comprehensive analysis of the global and segmental features of gait in patients with genetically confirmed inherited ataxias. Sixteen patients with autosomal dominant (spinocerebellar ataxia, SCA1 or 2) or recessive (Friedreich's ataxia, FRDA) ataxia were studied. We used a motion analysis system to record gait kinematic and kinetic data. We measured the mean values of global (time-distance parameters, COM displacement, support moment) and segmental gait parameters (joint displacement and inter-joint coordination), as both discrete and continuous variables, and their variability and correlations with International Cooperative Ataxia Rating Scale (ICARS) scores. We found a marked difference in all global gait parameters between the ataxic patients and the controls and close correlations between longer stride and stance duration and lower gait, posture and total ICARS scores. The only difference between the two patient groups was a shorter step length in the FRDA patients. As regards the segmental features, we found a significantly different waveform shape for all continuous kinematic and kinetic measures between the ataxic patients and the healthy controls, but only minor differences for the discrete measures. Intersegmental coordination evaluated using the continuous relative phase method revealed an irregular alternating joint behaviour without clear evidence of the synchronous pattern of alternating proximal/distal joint seen in healthy subjects. For almost all gait parameters we observed a markedly higher intra-subject variability in the ataxic patients versus the controls, which was strongly related to the clinical ICARS scores. Patients with chronic, progressive inherited ataxias lose the ability to "stabilize" a walking pattern that can be repeated over time. The most peculiar aspect of the gait of inherited ataxia patients, regardless the different genetic forms, seems to be the presence of increased variability of all global and segmental parameters rather than an invariant abnormal gait pattern.

인라인 스케이트 활주속력에 따른 T-Stop의 운동학적 분석

The purpose of this study was to investigate the kinematical analysis of T-stop motion by inline skate rolling speed. Six subjects were participated in the experiment(age: <TEX>$35.0{\pm}3.3$</TEX> yrs, weight: <TEX>$72.70{\pm}5.1\;kg$</TEX>, height: <TEX>$176.30{\pm}3.1\;cm$</TEX>, career: <TEX>$10.00{\pm}2.5$</TEX> yrs). The study method adopted 3-dimensional analysis and 2 cameras for filming to analyze the required displacement of center of mass, displacement of right and left hip joint, displacement of right and left knee joint, displacement of trunk tilt using by APAS. The results were as follows; In anterior-posterior displacement of COM, the faster rolling speed, the longer displacement at phase 2. In vertical displacement of COM, the faster rolling speed, the lower displacement. In medial-lateral displacement of COM, there was no significant on rolling speed. In angular displacement of right thigh segment, the faster rolling speed, the bigger displacement in X and Z axis. In angular displacement of left thigh segment, the faster rolling speed, the lower displacement in X axis. In angular displacement of right shank segment, the faster rolling speed, the bigger displacement in Z axis. In angular displacement of left shank segment, the faster rolling speed, the bigger displacement in X and Y axis. In angular displacement of trunk segment, the faster rolling speed, the bigger displacement in Z axis.

2A1-A05 ヒトの全身運動に対する外乱付加装置の開発

We developed a translational disturbance device for an analysis of stabilization mechanism about human whole body movement. The device can not only provide a direct disturbance on a subject, but also provide it via the other experimental devices like a treadmill. Moreover, it can be used in combination with a 3D motion capture system. In order to verify the validity of the experiment system, we measured the frequency response of the device and also we added a ramp disturbance against a subject using the device. The objective whole body movement was quiet standing. According to a bode diagram of the frequency response, the device has almost 0[dB] until 2.5[Hz], loading 100[kg]. As the human response to the ramp disturbance, we calculated the displacement of COM from the 3D motion data.

택견 기본 차기동작의 수행시간, 신체중심의 이동변위 및 발속도 비교 분석

택견 기본 차기동작의 수행시간, 신체중심의 이동변위 및 발속도 비교 분석

초등학교 학생들의 발달단계에 따른 던지기 동작의 운동역학적 분석

The purpose of this study was to examine the characteristics of throwing motion in the elementary school students from the developmental point of view. For the purpose of this, total of nine subjects(each of three students in five, third, and first grades) were participated. They were asked to throw the ball as far as they can and the motions were videotaped with the 30frames/sec and 1/500 shutter speed. The successful motions for each subject were selected for three dimensional analysis. The collected data were analyzed using DV express 1.0 and Kwon3D 3.0 softwares. The results obtained from this study were as follows; 1. Total time for the throwing motion of the first grade was longer than that of the fifth and third grades. 2. The resultant displacement and velocity of COM for the fifth and third grades were greater than that of the frist grade. 3. The first grade tended to flex the trunk forward excessively during the throwing motion. 4. The fifth grade tended to place the upper arm close to the sagital plane and move the forearm and hand freely. 5. Looking at the greater variability of the angular velocity of the hand segment, the fifth grade seemed to have faster and more flexible movement of the wrist. 6. There were somewhat differences in the patterns and magnitudes of ground reaction forces among the different grades.

Organization of postural responses following a rotational support surface perturbation, after TKA: Sagittal plane rotations

Proprioceptive dysfunction, related to osteoarthritis and total knee arthroplasty (TKA) may be related to changes in gait, and may result in balance impairment. This study examined the organization of postural responses to rotational support surface perturbations after TKA. Eight TKA patients and nine control participants volunteered. EMG was collected bilaterally from lower limb muscles. Kinematic data were collected using an OPTOTRAK system. The temporal pattern of muscle activation was preserved in both the surgical and sound limbs of the patient groups, while muscle activation amplitude was reduced. Knee joint angular displacement was reduced in both limbs among patients. COM displacement was not different. Patients demonstrated a different method in recovering posture control following a postural perturbation. Bilateral changes appear to reflect a simplification in the organization of the motor response, in response to the needs of the injured, or previously injured limb.

발레 숙련도에 따른 센터에서 Grand Battement Jeté á la seconde 동작의 운동학적 비교 분석

The purpose of this study was to investigate time of the phase, angle of the right ankle, knee, and hip joint, lateral angle of the trunk, mediolateral displacement of COM, and vertical displacement of COM between two groups while executing grand battement la seconde in a center exercise setting through 3D video analysis. The subjects participated in this study were skilled and unskilled 6 female ballet majors in Busan, respectively. The conclusions are as follows: 1. The time of the phase 2 was faster than P3. It shows a significant difference(p