Center Of Gravity Displacement Research Articles

Baduanjin is Better Balance Training Compared to Walking: A Cross-Sectional Study Based on Center of Gravity Trajectories.

It has already been demonstrated by previous studies that Baduanjin training can improve the body's balance. However, its biomechanical mechanism remains unknown. Center of gravity (COG) trajectory analysis is an essential biomechanical test to explore the balance ability of the human body.Previous studies have not used the COG trajectory analysis technique to research Baduanjin training. The study utilizes COG trajectory analysis to analyze the trajectory of COG during Baduanjin training and compare it with that of walking, which is a common exercise for improving balance and aerobic ability, to determine if Baduanjin exercises affect the COG more than walking. Eight healthy female college students performed the walking and the eight forms of Baduanjin, a total of nine motions. The lower body kinematics were captured by the Vicon Motion Capture and Analysis System, while the kinetic data were acquired by the Kistler 3D Force Platform. The data were imported into Visual 3D to process the trajectory of the COG displacement amplitude, velocity, and accelerationofeachmotion. The COG horizontal envelope areas were calculated by Origin 9.0 Software (Origin Lab, Northampton, Massachusetts, USA). Specific motions of Baduanjin provided significantly higher COG displacement amplitude, velocities, and acceleration training than walking. The F2 and F5 motions could provide a larger COG horizontal envelope area than walking. On the x-axis, F2 provided a greater COG displacement amplitude than walking, F1, F2, and F5 provided greater velocities, while all the motions provided greater accelerations. On the y-axis, all the motions except F2 provided greater COG displacement velocities and accelerations than walking. On the z-axis, F1-7 provided a greater COG displacement amplitude than walking, all the motions providedgreater velocities, while all the motions except F2 provided greater accelerations. Baduanjin training provides a more intense COGperturbation than walking, which may be a more challenging balance training than walking.

Effect of initial foot angle (IFA) on kinematics and dynamics of body during sit-to-stand transfer.

Sit-to-stand (STS) is considered the most common functional activities in daily life and the basis for other activities. The elderly and patients with lower limb disorders could not complete the STS motion very well due to limb pain and muscle weakness. Physiotherapist find that specific STS transfer strategies can make patients more easily to complete this task. However, few researchers pay attention to the effect of initial foot angle (IFA) on STS motion. Twenty-six healthy subjects were randomly selected to perform STS transfer experiment. The motion characteristic parameters of subjects under 4 different IFAs (nature, 0°, 15°, and 30°) were obtained, including the percentage of duration in each phase, the velocity of joints, rotation angle and angular velocity of joints (shoulder, hip and knee), center of gravity (COG) trajectory. the change of plantar pressure parameters, and dynamic margin of stability. By comparing the motion characteristic parameters obtained under different IFAs and carrying out statistical analysis, the influence of different IFAs on body kinematics and dynamics during STS task was further explored. The kinematic parameters obtained under different IFAs are significantly different. The percentage of duration in each phase of the STS transfer was different with different IFA, the main differences were in phase I and phase II. The phase I of U15 took 24.5% T, while phase I of N, U0 and U30 took about 20% T, and the maximum difference was (U15-U0) 5.4%. The phase II of U15 took the least time, about 30.8% T. When the IFA is nature (N) and 15°(U15), the trajectories of COG are basically in coincidence; when the IFA is 0°(U0) and 30°(U30), the displacement of COG in anterior-posterior direction is larger. The larger the IFA, the smaller the plantar pressure parameter. When the IFA is 15°, the COG is close to the center of limits of stability, which can provide a better stability. This paper summarizes the influence under 4 different experimental conditions of IFAs on STS transfer, so as to provide a starting point and bases for clinicians to develop rehabilitation training protocols and STS motion strategies for patient.

Compare the Differences of Head Strike Techniques between Different Standing Tobikomi Men Methods of Elite Female Kendo Athletes

<p>目的 : 針對不同重心站立法對女子劍道選手面部打擊技術之差異進行分析，以提升國內女子劍道選手技術水準。方法：以十名女子劍道選手為研究參與者，平均年齡 25.9 ± 7.1歲、平均身高 160.2 ± 4cm、平均體重 56.3 ± 9.6kg、運動年齡 11.5 ± 7.4年。在測力板上分別使用重心在前與重心在後兩種站立法，進行面部打擊，並同步使用 6部高速攝影機分析打擊過程。以成對樣本 t 檢定，分析重心水平位移、重心垂直位移、下蹲期重心垂直位移、竹劍垂直擺盪位移、整體打擊時間、離地瞬間重心水平速度、離地瞬間重心垂直速度、最大推蹬力等參數，以標準差、平均數、t值與 p值呈現結果，顯著水準設為 α = .05。結果：不同重心站立法在重心垂直 (p = .005)和水平 (p = .010)位移達顯著差異、後腳推蹬反作用力有顯著差異 (p = .022)，重心在前站立法推蹬地面反作用力 (1.63 BW%) 大於重心在後站立法 (1.55 BW%)，重心在後站立法進行攻擊，有較小的重心垂直位移 (8.90cm)，和較大的重心水平位移 (53.90cm)。結論：重心在後站立法是較合適選擇的站立法，攻擊動作較為穩定，而重心在前站立法則是能提供較大的推蹬力。在比賽場上採用重心在後站立法時，有較好的攻擊動作穩定性，且在重心水平位移與重心垂直位移表現皆優於重心在前站立法，此結果提供教練或選手作訓練及比賽參考，以提升運動表現。</p> <p> </p><p>Purpose: This study is to analyze the differences of head strike techniques between different Standing Tobikomi Men Methods of female kendo athletes in order to improve the development of domestic kendo. Methods: 10 female kendo athletes were recruited in this study, with an average age of 25.9 ± 7.1 years, an average height of 160.2 ± 4 cm, an average weight of 56.3 ± 9.6 kg, and an average sports age of 11.5 ± 7.4 years. All participants conducted head strikes on the force plate with 2 different standing methods, one with body weight on the front foot (front standing), the other with body weight on the back foot (back standing), and 6 high-speed cameras were used to analyze the strike at the same time. Paired sample T test was used to analyze the following parameters: horizontal and vertical displacement of center of gravity (COG), the vertical displacement of the center of gravity during the squatting period, the vertical displacement of the bamboo sword, the overall strike time, the horizontal instantaneous speed of COG at the moment of leaving the ground, the maximum pushing force. Data was presented as standard deviation, mean, t-value, and p-value, with the level of significance set at α = .05. Results: There were significant differences in vertical (p = .005) and horizontal (p = .010) displacement of the center of gravity, and in the reaction force of the back foot (p = .022). The ground reaction force during pushing off is greater in the front standing (1.63 BW%) than the back standing (1.55 BW%). The back standing had smaller vertical displacement of COG (8.90 cm) and larger horizontal displacement of COG than the front standing method. Conclusions: The back standing is more suitable to conduct head strike with the strikes being more stable. While front standing could provide greater pushing force. The back standing makes the strike more stable and both the horizontal and vertical displacement of COG were smaller than front standing. The founding of this study could provide coaches and athletes a reference to improve performance when training and competing</p> <p> </p>

Design, development and experimental validation of a lightweight dual-arm aerial manipulator with a COG balancing mechanism

In this work, we present the design, fabrication, and experimental validation of a lightweight, low inertia dual-arm manipulator with a center of gravity (COG) balancing mechanism, specifically designed for aerial manipulation missions. The developed system, consisting of the dual-arm base and two arms with 6 degrees of freedom (DOFs) each, weighs 2.5 kg in total with a maximum payload of 1.0 kg per arm. The dual-arm system is designed such that it can be attached to different multirotors without making major design modifications. In addition, the design of the arms is conceived to decrease the inertia of the arms by utilizing a timing belt-based transmission mechanism. Moreover, the proposed dual-arm design employs prismatic joints to introduce the following distinctive features: 1) ability of each arm to dynamically adjust its COG for better flight performance; 2) fully independent control of each arm for performing different tasks simultaneously; 3) extended workspace and reach of the arms for enhancing operational capability and improving safety during aerial manipulation missions. Since the proposed design has low inertia and a compensation mechanism to deal with the disturbances caused by the COG change, the developed dual-arm system can be mounted on multirotors equipped with standard autopilots, opening the door for the widespread use of dual-arm manipulators with the commercially available UAV platforms. To ensure the robustness of the mechanical structure, an analysis using finite element methods (FEM) is conducted. Extensive experimental flight tests are performed to evaluate the proposed dual-arm design with a hexarotor equipped with a common off-the-shelf autopilot. The experimental results show that the influence of the arms motion over the hexarotor stability is minor in contactless flight due to the low weight and inertia of the proposed dual-arm design. Furthermore, better hovering performance is achieved by exploiting the ability of the proposed design to compensate the dual-arm COG displacement.

Dimensionless Model-Based System Tracking Via Augmented Kalman Filter for Multiscale Unmanned Ground Vehicles

In recent years, many unmanned vehicle designs and autonomous driving functions have been introduced in the automotive industry to increase the safety and versatility of multiple vehicle designs. It is critical to select a plant vehicle model and a compact uncertainty representation regardless of the vehicle scale for vast deployment. This article introduces a dimensionless representation of a dynamic vehicle model that is suitable for generalized dynamic analysis. Demonstrations included in this article showed that the compact uncertainty bounds of the dimensionless parameters could be used to generate an adaptive observer suitable for full-sized and corresponding scaled vehicles. The proposed dimensionless model-based observer can assess motion states, mass, center of gravity displacement, and the tire stiffness online with common onboard inertial measurement unit (IMU). The effectiveness and sensitivity of the proposed technique are highlighted through simulations and experiments on scaled test vehicles.

Ankle taping and bracing does not change static and dynamic balance in volleyball players

The purpose of this study was to compare the effects of nonelastic adhesive tape, dynamic bracing, and no-tape/brace on static and dynamic balance during single-leg stance in women’s college volleyball. Seventeen young uninjured players (18.94 ± 2.49 years; 1.71 ± 0.05 m; 65.45 ± 9.49 kg; 9.2 ± 4.1 years played; 4 ± 1 weekly training frequency) were submitted to three conditions presented in randomized order: dynamic bracing; nonelastic adhesive tape and no-tape/brace. In all conditions, the center of gravity displacement (total displacement, TD; anteroposterior displacement, APD and mediolateral displacement, MLD) of the dominant and non-dominant lower limb (DLL and NDLL) was assessed using the static and dynamic platform of the Biodex Balance System. The ANOVA (three-way) test with repeated measures was applied, considering a 5% significance level. The results showed no interaction between any of the independent factors in all displacements (p > 0.05). However, there was a significant main level effect for TD (p = 0.001, mean difference = 1.1°) and MLD (p = 0.013, mean difference = 0.30°), with greater displacement in the dynamic level compared to its static counterpart. There was also a significant main limb effect for APD (p = 0.003, mean difference = 0.73°) and MLD (p ≤ 0.001, mean difference = 0.60°), with a higher degree of instability in MND when compared to MD. In conclusion, the data indicated that the use of nonelastic tape and bracing was not superior to the no-tape/brace condition in controlling center of gravity displacement during single-leg stance.

Relationship between Leg Stiffness and Kinematic Variables According to the Load while Running

Objective: This study aimed to investigate the relationship between leg stiffness and kinematic variables according to load while running. Method: Participants included eight healthy men (mean age, <TEX>$22.75{\pm}1.16years$</TEX>; mean height: <TEX>$1.73{\pm}0.01m$</TEX>; mean body weight, <TEX>$71.37{\pm}5.50kg$</TEX>) who ran with no load or a backpack loaded with 14.08% or 28.17% of their body weight. The analyzed variables included leg stiffness, ground contact time, center of gravity (COG) displacement and Y-axis velocity, lower-extremity joint angle (hip, knee, ankle), peak vertical force (PVF), and change in stance phase leg length. Results: Dimensionless leg stiffness increased significantly with increasing load during running, which was the result of increased PVF and contact time due to decreased leg lengths and COG displacement and velocity. Leg length and leg stiffness showed a negative correlation (r = -.902, <TEX>$R^2=0.814$</TEX>). COG velocity showed a similar correlation with COG displacement (r = .408, <TEX>$R^2=.166$</TEX>) and contact time (r = -.455, <TEX>$R^2=.207$</TEX>). Conclusion: Dimensionless leg stiffness increased during running with a load. In this investigation, leg stiffness due to load increased was most closely related to the PVF, knee joint angle, and change in stance phase leg length. However, leg stiffness was unaffected by change in contact time, COG velocity, and COG displacement.

Integration Frequency Response of Human Dynamic Balance Under Passive Motion Stimulus by Using Center of Gravity

This study investigated the frequency response of body oscillations in the medio-lateral (M-L) direction during upright stance and proposes an M-L balance assessment method. Previous investigations have commonly used a visual tracking task and measured the displacement of the center of pressure, but these methods are affected by the body’s subjective factors and do not reliably represent human dynamic balance. In this study, 10 subjects were settled on a 6-DOF motion platform in a specific posture, and the passive motion stimulus was tracked using a sinusoidal waveform with a frequency range of 0.05-1.5 Hz. The Bode diagram, which consisted of the magnitude and phase-shift between the motion of platform and the body’s center of gravity (COG), was obtained by measuring the COG displacement. The results show that, at 0.5-1.0 Hz, the subjects had a higher probability of losing their balance. The mean cut-off frequency (COF) was 0.62 Hz, so the bandwidth of the body oscillation was 0.1-0.6 Hz. Furthermore, the COF could be used to quantify balance ability, i.e. a higher COF corresponded to better balance ability. Additionally, the mean resonance frequency was 0.44 Hz, which reflected spontaneous body sway. In conclusion, this study determined the integration frequency response of human dynamic balance under passive motion stimulus using COG, and proposed a more objective and accurate method for evaluating balance ability.

Anxiety provokes balance deficits that are selectively dopa-responsive in Parkinson’s disease

Previous research has suggested that balance impairments may be linked to anxiety in PD, yet there is little empirical evidence to support this link in PD. This study aimed to evaluate the influence of anxiety on balance, and also examine whether dopaminergic treatment modulates the influence of anxiety on balance. Forty-two participants (10 high anxious PD [HA–PD]; 11 low anxious PD [LA–PD], 21 controls [HC]) performed 10 quiet standing trials on a force platform in two virtual environments: LOW threat; on a plank located on the ground; HIGH threat; on an elevated plank. After each 30-s trial, participants rated their anxiety. PD participants were tested both ON and OFF dopaminergic medication, and center of gravity (COG) deviations in anterior–posterior (AP) and medio-lateral (ML) directions were recorded. Results showed that all groups reported significantly greater levels of anxiety when standing in the HIGH condition compared to the LOW and HA–PD reported greater levels of anxiety compared to both other groups. All participants significantly reduced their COG position to be closer to center in the ML plane during the HIGH compared to LOW threat condition. HA–PD participants were the only group to reduce their lean significantly in the AP plane while standing in the HIGH compared to the LOW condition. HA–PD participants also had significantly greater variability in the COG displacement in both the AP and ML planes compared to LA–PD participants. Although dopaminergic medication significantly reduced self-reported anxiety, it had limited effects on balance. In conclusion, this study provides strong evidence that anxiety does influence balance control in PD, especially those who are highly anxious. Dopamine appears to modulate anxiety, but further research is needed to evaluate whether dopaminergic treatment is optimal for anxiety induced balance deficits.

Postural Control in Healthy Young Adults with and without Chronic Motion Sensitivity

Background: Postural control requires complex processing of peripheral sensory inputs from the visual, somatosensory and vestibular systems. Motion sensitivity and decreased postural control are influenced by visual-vestibular con flicts. The purpose of this study was to measure the difference between the postural control of healthy adults with and without history of sub-clinical chronic motion sensitivity using a computerized dynamic posturography in a virtual reality environment. Sub-clinical chronic motion sensitivity was operationally defined as a history of avoiding activities causing dizziness, nausea, imbalance, and/or blurred vision without having a related medical diagnosis. Methods: Twenty healthy adults between 22 and 33 years of age participated in the study. Eleven subjects had sub-clinical chronic motion sensitivity and 9 subjects did not. Postural control was measured in both groups using the Bertec Balance Advantage-Dynamic Computerized Dynamic Posturography with Immersion Virtual Reality (CDP-IVR). The CDP-IVR reports an over-all equilibrium score based on subjects’ center of gravity displacement and postural sway while immersed in a virtual reality environment. Subjects were tested on stable (condition 1) and unstable (condition 2) platform conditions. Results: There was no significant difference between the two groups in terms of mean age, height, weight, body mass index in kg/m2, postural control scores for conditions 2, and average (p>0.05). However, significant differences were observed in mean postural control for condition 1 between groups (p=0.03). Conclusions: Results of this study suggest that healthy young adults without chronic sub-clinical motion sensitivity have better postural control than those with chronic sub-clinical motion sensitivity. Further investigation is warranted to explore wider age ranges with larger samples sizes as well as intervention strategies to improve postural control.

A Kinematic Approach to Understanding Performance in Upper-Extremity Function during a Goal-Directed Man-Machine Interface Task in a Submariner Environment.

In December of 2014, the United States Congress funded a fundamental shift in the recruiting policy of the US Navy Submarine Force to include the integration of women. As a result, design modifications became necessary, especially those that facilitate integration without inflating costs. Current cost levels associated with new submarine design(s) are maintained through the use of legacy components and systems. Additionally, many of the systems aboard are computer controlled, necessitating man-machine interfaces. As common practice, military activities that involve man-machine interfaces have always focused on the dexterity of the hands, often neglecting the role of movement in the task; therefore, there is a need to understand upper-extremity kinematics issues associated with man-machine interfaces. Joint kinematics of the right upper extremity of 10 subjects was measured using an optoelectronic motion capture system. Center of gravity displacements were measured using a force plate during touchscreen movement tasks paced by six different movement frequencies from a metronome (0, 1.0, 1.3, 1.7, 2.0, and 2.7 Hz). Results showed no significant difference in touch accuracy, task completion time, shoulder and elbow angular displacements, and shoulder and elbow flexion/extension velocity; however, a significant difference (0.002; p ≤ 0.05) in shoulder adduction/abduction velocity was observed. In arranging systems and components in submarine and surface vessel environments, consideration in not only providing a means of adjustability (e.g., height, proximity, and orientation) but in the dimensions of the systems and components themselves must also be considered based on the required operation.

Generation and Analyses of the Reinforced Wave Gait for a Mammal-Like Quadruped Robot

The statically stable gait control of a mammal-like quadruped robot that provides an adequate or stable manner of traversing over irregular terrain was addressed. The reinforced wave gait which integrates new parameters of the lateral offset and displacements of the center of gravity (COG) based on the profiles of standard wave gait was investigated. The continuous and discontinuous motion trajectory of a robot's COG in the periodic reinforced wave gait could be realized. The longitudinal and lateral stability margins of a reinforced wave gait were formulated for the gait generation and control of a quadruped robot. Moreover, the effects of the lateral offset on the stability, velocity and the energy efficiency were studied in details. The reinforced wave gait with lateral sway motion adequately improved the stability, and two particular gait patterns that involve the lateral sway motion for a maximal velocity and maximum achievable stability were described. With consideration of a quadruped robot with asymmetric carrying loads on its body, a scheme that relates to the gait parameters of the displacement of a robot's COG to avoid losing stability was proposed. The simulation and experimental results about the effects of lateral offset added in the reinforced wave gait on the minimum power consumption during a quadruped robot walking on a flat terrain indicated that the reinforced wave gait with a larger lateral offset would generate a better wave gait with a higher velocity and energy efficiency.

Kinematic, Cardiopulmonary, and Metabolic Responses of Overweight Runners While Running at Self-Selected and Standardized Speeds

ObjectiveTo determine the differences in kinematic, cardiopulmonary, and metabolic responses between overweight and healthy weight runners at a self-selected and standard running speed. DesignComparative descriptive study. SettingTertiary care institution, university-affiliated research laboratory. ParticipantsOverweight runners (n = 21) were matched with runners of healthy weight (n = 42). MethodsParticipants ran at self-selected and standardized speeds (13.6 km/h). Sagittal plane joint kinematics were captured simultaneously with cardiopulmonary and metabolic measures using a motion capture system and portable gas analyzer, respectively. Main Outcome MeasurementsSpatiotemporal parameters (cadence, step width and length, center of gravity displacement, stance time) joint kinematics, oxygen cost, heart rate, ventilation and energy expenditure. ResultsAt the self-selected speed, overweight individuals ran slower (8.5 ± 1.3 versus 10.0 ± 1.6 km/h) and had slower cadence (163 versus 169 steps/min; P < .05). The sagittal plane range of motion (ROM) for flexion-extension at the ankle, knee, hip, and anterior pelvic tilt were all less in overweight runners compared to healthy weight runners (all P < .05). At self-selected speed and 13.6 km/h, energy expenditure was higher in the overweight runners compared to their healthy weight counterparts (P < .05). At 13.6 km/h, only the frontal hip and pelvis ROM were higher in the overweight versus the healthy weight runners (P < .05), and energy expenditure, net energy cost, and minute ventilation were higher in the overweight runners compared to the healthy weight runners (P < .05). ConclusionAt self-selected running speeds, the overweight runners demonstrated gait strategies (less joint ROM, less vertical displacement, and shorter step lengths) that resulted in cardiopulmonary and energetic responses similar to those of healthy weight individuals.

Soccer-specific Fatigue Decreases Reactive Postural Control with Implications for Ankle Sprain Injury

To quantify the influence of soccer-specific fatigue on reactive dynamic balance, ten male professional soccer players (age 24.7 ± 4.4 yr, body mass 77.1 ± 8.3 kg, VO2max 63.0 ± 4.8 ml·kg·min–1) completed an exercise protocol replicating the activity profile of match-play. Pre-exercise, and at 15 min intervals, players completed three balance tasks requiring response to a system perturbed to induce either plantar flexion of the ankle or inversion of the ankle (by rotation or translation). ANOVA revealed a significant main effect for exercise duration in each task, with both reaction time and total centre of gravity displacement tending to increase during each half. In all three trials there was a significant increase in medio-lateral and anterior-posterior displacement, the planar perturbation of the platform evoking a multi-angular response. Dynamic balance performance decreased as a function of time during each half, suggesting a greater risk of injuries at these specific times, in accord with epidemiological observations of ankle sprain injury.

체감형 스키 시뮬레이터 개발을 위한 플루크보겐 동작의 운동역학적 비교

The purpose of this study was to compare pflugbogen's biomechanical characteristics between on the ski simulator and snowed ski slope to develop interactive ski simulator. Nine ski instructors(sex: male, age: <TEX>$29.6{\pm}5.4yrs$</TEX>, height: <TEX>$176.0{\pm}5.6cm$</TEX>, body mass: <TEX>$76.0{\pm}14.0kg$</TEX>) belong to Korean Ski Instructors Association participated in this research. 24 Infrared cameras for snowed ski slope experiment and 13 infrared camera for ski simulator experiment were installed near by path of pflugbogen. The participants did pflugbogen on the snowed ski slope and the ski simulator both. During the experiment, the participants weared motion capture suit with infrared reflective makers on it, and plantar pressure sensors in ski boots, so that ski motion and plantar pressure data were collected together. Displacement of COG(center of gravity) movements, trunk flexion/extension angle, adduction/abduction angle, and plantar pressure data were significantly different between on the simulator and ski slope. However, percentage of time of COG movement in the phases during medial/lateral and anterior/posterior movement were not significantly different. Findings indicate that the difference between two groups occurred because the ski simulator's drive mechanism is different from ski motion on the slope. In order to develop the ski simulator more interactively for pflugbogen, the ski simulator's drive mechanism need to be reflected 3D motion data of pflugbogen on the slope that were purposed in this research.

석문일월무예 음양보법의 숙련성에 따른 보행 패턴의 하지 운동학 및 운동역학적 특성

The purpose of this study was to quantify kinematic and kinetic characteristics of Yin-yang Bo gait according to their motor expertise, one of the Seokmun Ilwol martial art gait patterns. Yin-yang Bo gait pattern shows initial forefoot contact instead of heel contact, and increased time of stance phase time, internal-external rotation of ankle-knee-hip joints and pelvic. It aims to produce and store the more energy through continuous homeostasis of center of gravity (COG) and performance of stretch-shortening cycle. Some of these characteristics also were similar to the gait modification strategies for reducing knee adduction moment such as toe-out progression, medial thrust, internal rotation of hip joint. To identify the characteristics, four factors of expert Yin-yang Bo gait performance group were compared to that of none expert group; 1) angles of COG displacement and rotation 2) distal joint pre-rotation in internal-external rotation of ankle-knee-hip joints and pelvic, 3) invariability pelvic potential and pelvic segment total energy 4) knee abduction moment. Six healthy(three male) subjects participated in the experiment to perform Yin-yang gait pattern. Three-dimensional and force plate data were collected. Kinematic and kinetic data were compared between two groups using t-tests. Results showed that 1) the peak point of COG internal rotation angle was reduced in expert group, 2) kneeexternal and hip joint -internal and pelvic rotation angle peak frames were more near points in expert group.

Metabolic, Cardiopulmonary, and Gait Profiles of Recently Injured and Noninjured Runners

ObjectiveTo examine whether runners recovering from a lower body musculoskeletal injury have different metabolic, cardiopulmonary, and gait responses compared with healthy runners. DesignCross-sectional study. SettingResearch laboratory at an academic institution. MethodsHealthy runners (n = 50) were compared with runners who were recently injured but had returned to running (n = 50). Both groups were participating in similar cross-training modalities such as swimming, weight training, biking, and yoga. Running gait was analyzed on a treadmill using 3-dimensional motion capture, and metabolic and cardiopulmonary measures were captured simultaneously with a portable metabolic analyzer. Main Outcome MeasuresRate of oxygen consumption, heart rate, ventilation, carbohydrate and fat oxidation values, gait temporospatial parameters and range of motion measures (ROM) in the sagittal plane, energy expenditure, and vertical displacement of the body's center of gravity (COG). ResultsThe self-selected running speed was different between the injured and healthy runners (9.7 ± 1.1 km/h and 10.6 ± 1.1 km/h, respectively; P = .038). No significant group differences were noted in any metabolic or cardiopulmonary variable while running at the self-selected or standard speed (13.6 km/h). The vertical displacement of the COG was less in the injured group (8.4 ± 1.4 cm and 8.9 ± 1.4, respectively; P = .044). ROM about the right ankle in the sagittal plane at the self-selected running speed during the gait cycle was less in the injured runners compared with the healthy runners (P < .05). ConclusionsRunners with a recent lower body injury who have returned to running have similar cardiopulmonary and metabolic responses to running as healthy runners at the self-selected and standard speeds; this finding may be due in part to participation in cross-training modes that preserve cardiopulmonary and metabolic adaptations. Injured runners may conserve motion by minimizing COG displacement and ankle joint ROM during a gait cycle.

Unilateral upper extremity lymphedema deteriorates the postural stability in breast cancer survivors.

Aim of the studyThere is little known about any change in postural balance caused by asymmetrical volume increase due to unilateral upper extremity lymphedema in patients who underwent breast surgery. The aim of this study was to determine whether there is a change in postural balance by measuring postural sway velocity (PSV), center of gravity (CoG) displacement and directional control (DCL) in patients with unilateral upper extremity lymphedema in breast cancer survivors.Material and methodsEighteen females 38–60 (M = 53) years old diagnosed with upper extremity lymphedema due to breast cancer surgery, and 18 healthy females with similar ages (M = 52.5) were assessed using the Balance Master system (Neuro Com, Clackamas, USA). Unilateral stance (US) and bilateral stance (BS) tests in eyes open and closed conditions and the limit of stability (LOS) test were applied to quantify postural sway velocity (PSV), CoG displacement, and directional control (DCL).ResultsThe lymphedema group showed a significant increase in PSV in the US test on the ipsilateral leg with eyes open (p = 0.02) and eyes closed (p = 0.005) as well as on the contralateral leg with eyes open (p = 0.004) and eyes closed (p = 0.0001). Average displacement and position of the CoG were 25% of LOS (p = 0.0001) towards the lymphedema side and 60.6 degrees respectively. DCL in the lymphedema group was significantly lower in forward (p = 0.0001), back (p = 0.003), ipsilateral (p = 0.002), and contralateral (p = 0.03) directions.ConclusionsThese findings suggest that unilateral upper extremity lymphedema may have challenging effects on postural balance.

Particular adaptations to potentially slippery surfaces: The effects of friction on consecutive postural adjustments (CPA)

This research deals with the postural adjustments that occur after the end of voluntary movement (“consecutive postural adjustments”: CPAs). The influence of a potentially slippery surface on CPA characteristics was considered, with the aim of exploring more deeply the postural component of the task-movement. Seven male adults were asked to perform a single step, as quickly as possible, to their own footprint marked on the ground. A force plate measured the resultant reaction forces along the antero-posterior axis (Rx) and the centre of pressure (COP) displacements along the antero-posterior and lateral axes (Xp and Yp). The velocity of the centre of gravity (COG) along the antero-posterior axis and the corresponding impulse (∫Rxdt) were calculated; the peak velocity (termed “progression velocity”: VxG) was measured. The required coefficient of friction (RCOF) along the progression axis (pμx) was determined. Two materials, differing by their COF, were laid at foot contact (FC), providing a rough foot contact (RoFC), and a smooth foot contact (SmFC) considered to be potentially slippery. Two step lengths were also performed: a short step (SS) and a long step (LS). Finally, the subjects completed four series of ten steps each. These were preceded by preliminary trials, to allow them to acquire the necessary adaptation to experimental conditions. The antero-posterior force time course presented a positive phase, that included APAs (“anticipatory postural adjustments”) and step execution (STEP), followed by a negative one, corresponding to CPAs. The backward impulse (CPI) was equal to the forward one (BPI), independently of friction and progression velocity. Moreover, VxG did not differ according to friction, but was faster when the step length was greater. Last CPA peak amplitudes (pCPA) were significantly greater and CPA durations (dCPA) shorter for RoFC and conversely for SmFC, contrary to APA. Finally, the results show a particular adaptation to the potentially slippery surface (SmFC). They suggest that adherence modulation at foot contact could be one of the rules for controlling COG displacement in single stepping. Consequently, the actual coefficient of friction value might be implemented in the motor programme at a higher level than the voluntary movement specific parameters.

Three-Dimensional Kinematic Analysis of the Snatch Technique for Lifting Different Barbell Weights

The purpose of this study was to investigate the effects of increased barbell loads on barbell and body kinematics of the snatch lifts at 60, 80, and 100% of 1 repetition maximum and to evaluate the biomechanics of snatch technique. The study was performed on 7 elite male weightlifters of the Turkish national team. Four cameras operating at 50 fields per second were used to record the lifts. For 3D kinematic analysis of center of gravity (CG) and barbell movement, the points on the body and the barbell were digitized by using an Ariel Performance Analysis System. There were significant differences between the vertical work values (p < 0.05). The power values of the 3 snatch lifts were also found to be significantly different (p < 0.05). Another significant difference (p < 0.05) was observed between maximum vertical displacement of the barbell, maximum vertical velocity of the barbell, maximum vertical displacement of CG, the vertical velocity of CG during the turnover under the barbell. The results demonstrated that vertical and horizontal kinematics of the barbell and body decreased at the pull phase of the snatch technique as the barbell load increased. The power output during the second pull increased although the work done did not change, whereas work and power output increased during the first pull phase depending on the increase in the barbell weight. The finding of this study suggested that weightlifters had to perform the turnover under the barbell and the catch phase faster, because when the barbell weight was increased at snatch lift, vertical kinematics of the barbell decreased.