Center Of Mass Acceleration Research Articles

Evaluation of instability in patients with chronic vestibular syndrome using dynamic stability indicators.

Gait abnormalities are common in patients with chronic vestibular syndrome (CVS), and stability analysis and gait feature recognition in CVS patients have clinical significance for diagnosing CVS. This study explored two-dimensional dynamic stability indicators for evaluating gait instability in patients with CVS. The Center of Mass acceleration (COMa) peak of CVS patients was significantly faster than that of the control group (p < 0.05), closer to the back of the body, and slower at the Toe-off (TO) moment, which enlarged the Center of Mass position-velocity combination proportion within the Region of Velocity Stability (ROSv). The sensitivity, specificity, and accuracy of the Center of Mass velocity (COMv) or COMa peaks were 75.0%, 93.7%, and 90.2% for CVS patients and control groups, respectively. The two-dimensional ROSv parameters improved sensitivity, specificity, and accuracy in judging gait instability in patients over traditional dynamic stability parameters. Dynamic stability parameters quantitatively described the differences in dynamic stability during walking between patients with different degrees of CVS and those in the control group. As CVS impairment increases, the patient's dynamic stability decreases. This study provides a reference for the quantitative evaluation of gait stability in patients with CVS.

Gait balance recovery after tripping: The influence of walking speed and ground inclination on muscle and joint function

Reactive lower limb muscle function during walking plays a key role in balance recovery following tripping, and ultimately fall prevention. The objective of this study was to evaluate muscle and joint function in the recovery limb during balance recovery after trip-based perturbations during walking. Twenty-four healthy participants underwent gait analysis while walking at slow, moderate and fast speeds over level, uphill and downhill inclines. Trip perturbations were performed randomly during stance, and lower limb kinematics, kinetics, and muscle contribution to the acceleration of the whole-body centre of mass (COM) were computed pre- and post-perturbation in the recovery limb. Ground slope and walking speed had a significant effect on lower limb joint angles, net joint moments and muscle contributions to support and propulsion during trip recovery (p < 0.05). Specifically, increasing walking speed during trip recovery significantly reduced hip extension in the recovery limb and increased knee flexion, particularly when walking uphill and at higher walking speeds (p < 0.05). Gluteus maximus played a critical role in providing support and forward propulsion of the body during trip recovery across all gait speeds and ground inclinations. This study provides a mechanistic link between muscle action, joint motion and COM acceleration during trip recovery, and underscores the potential of increased walking speed and ground inclination to increase fall risk, particularly in individuals prone to falling. The findings of this study may provide guidelines for targeted exercise therapy such as muscle strengthening for fall prevention.

Comparing the Effects of an Off-Ice Sprint-Change of Direction Task on Trunk Kinematics and Gait Laterality in Collegiate Ice Hockey Players

Laterality preferences are intrinsic in most physical activities, and ice hockey is one domain wherein these preferences might influence performance. Biomechanical laterality between dominant and nondominant (or preferred and nonpreferred) limbs is believed to be an advantageous attribute that is linked with skilled performance. Yet little is known about the implications of motor asymmetries for skilled performers in dynamic, time-constrained, team-based activities in an off-ice environment. This can be extended to when player position is considered, notably for those playing in a defensive or an offensive position. In this study, fourteen semi-professional collegiate male ice hockey players (age: 21.87 ± 2.98 years; BMI: 25.26 ± 3.21 kg/m) performed a randomized repeated 15 m sprint-change of direction task. Assessments of lower limb laterality were carried out as participants commenced the 15 m sprint change of direction task in both a right and left foot rear setback position. Biomechanical laterality between right and left rear foot setback positions was inferred by an ActiGraph GTx3 triaxial accelerometer that was located on the participants’ spinous process, representing the trunk centre of mass (CoM). Overall, ANOVA results indicated significant differences across all sprint split times between the right and left foot rear setback positions, with times significantly quicker when players commenced in a right rear foot setback position (p &lt; 0.001). ANOVA revealed significant differences in trunk CoM acceleration between in a right and left rear setback position, specifically during the initial 0–10 m sprint split, with offensive players observed to have lesser trunk anteroposterior and vertical CoM acceleration (p = 0.05) and during the final 5 m sprint split (p = 0.002, d = 0.7), despite overall smaller effect sizes seen in the left foot rear setback position. It appears that starting with the foot in a right rear setback position results in quicker 15 m performance times and concurrent lower magnitudes of trunk CoM acceleration. Although we demonstrated that offensive players were quicker and displayed less trunk CoM acceleration, we recommend that future studies use a greater number of participants for inter-limb symmetry in these movement tests.

Acute effect of short-duration static stretching exercises on dynamic balance in U-14 female athletes

Purpose The acute effects of static stretching (SS) on dynamic balance, a key fitness component that contributes to injury prevention, has been and is still a subject of significant debate. This study aimed to investigate the acute effect of short-duration SS exercises on dynamic balance following different recovery durations in youth female volleyball players. Methods Thirteen volunteers U-14 female players were included. Eight random assessments were carried-out on separate days. They consisted of 2D-kinematic analysis of frontal and/or sagittal balance of the center of mass (COM) displacement, velocity, and acceleration on wobble board conducted without SS, immediately after and following 2 and 10 minutes of SS. Results Repeated-measures ANOVA showed a significant difference between conditions in the velocity (p=0.002 to 0.049; d=0.844 to 2.200) and the acceleration (p=0.014 to 0.021; d=1.532 to 1.657) of the COM in both frontal and sagittal planes sway. Post-hoc analysis revealed decreased COM velocity (p=0.001 to 0.030; d=2.501 to 6.750) and acceleration (p=0.001 to 0.030; d=2.501 to 6.750) in the frontal plane, regardless of the recovery time. The most prominent decrease in both parameters was observed immediately after SS (p=0.001 to 0.013; d=2.907 to 6.750). However, in the sagittal balance, we observed an immediate increase in COM acceleration following SS (p&lt;0.001; d=4.223). Conclusions Short-duration SS leads to improved dynamic balance, particularly on the frontal plane, with the most favorable effect observed immediately after stretching. Practically speaking, short-duration SS appears to be an effective exercise modality for inducing acute enhancements in dynamic balance among youth female volleyball players.

Development and Validation of a System for Game Control Based on a Force Plate

A force plate is a device that measures the ground reaction force caused by a shift in the human body’s center of mass (CoM). Using a controlled change in the human body’s CoM, the human body’s center of pressure (CoP) is shifted in a 2D plane, along with an acceleration of the CoM along the plane perpendicular to the force plate, which allows for a generation of reference values for game control. In this paper, the development and validation of a system for game control based on a force plate are described. The game control system consists of a force plate, an electronic board used for measuring and PC communication via USB, and a PC application for data acquisition, system calibration, and game control. Based on the measured values of the player’s CoP and the CoM acceleration along a plane perpendicular to the force plate, the game control system simulates pressing the UP, DOWN, RIGHT, LEFT, and SPACE keyboard keys or moving the mouse and clicking the left mouse button, which allows players to control simple games. A mathematical model has been developed for the game control system which includes running system calibration procedures in the system for each individual player. The mechatronic game control system is described in detail, and experiments were run on said system for the purpose of system validation.

Overground walking while using a virtual reality head mounted display increases variability in trunk kinematics and reduces dynamic balance in young adults

AbstractThis study analyzed the effects of walking freely in virtual reality (VR) compared to walking in the real-world on dynamic balance and postural control. For this purpose, nine male and twelve female healthy participants underwent standard 3D gait analysis while walking randomly in a real laboratory and in a room-scale overground VR environment resembling the real laboratory. The VR was delivered to participants by a head-mounted-display which was operated wirelessly and calibrated to the real-world. Dynamic balance and postural control were assessed with (1) the margin of stability (MOS) in the anteroposterior (AP-MOS) and mediolateral (ML-MOS) directions at initial-contact, (2) the relationship between the mediolateral center of mass (COM) position and acceleration at mid-stance with subsequent step width, (3) and trunk kinematics during the entire gait cycle. We observed increased mediolateral (ML) trunk linear velocity variability, an increased coupling of the COM position and acceleration with subsequent step width, and a decrease in AP-MOS while walking in VR but no change in ML-MOS when walking in VR. Our findings suggest that walking in VR may result in a less reliable optical flow, indicated by increased mediolateral trunk kinematic variability, which seems to be compensated by the participants by slightly reweighing sensorimotor input and thereby consciously tightening the coupling between the COM and foot placement to avoid a loss of balance. Our results are particularly valuable for future developers who want to use VR to support gait analysis and rehabilitation.

Intelligent feedforward gust alleviation based on neural network

This paper proposes a neural network-based intelligent feedforward gust alleviation framework, which includes a neural network identification model and a neural network controller. A neural network training dataset is formed by collecting flight data and the gust data encountered during the aircraft flight. A neural network identification model is first trained to accurately predict the aircraft’s output. Then, based on the output of the identification model and the collected flight data, the parameters of the time-delay neural network controller are obtained through a learning process. The simulation results show that the designed intelligent controller has good gust alleviation effects for both continuous turbulence excitation and discrete gust excitation. For example, when the aircraft is 40000 kg and the flight speed is 0.81Ma, the controller achieves a 67.82% reduction in wingtip acceleration and a 35.90% reduction in center of mass acceleration under continuous turbulence excitation. When considering the measurement uncertainties, such as noise existing in the collected data, the trained controller can still achieve an acceptable gust alleviation effect. Finally, considering a flight in which the aircraft mass is constantly changing, the intelligent controller, which continuously learns from new flight data, maintains a good gust alleviation effect throughout the flight.

Absent loading response knee flexion: The impact on gait kinetics and centre of mass motion in individuals with unilateral transfemoral amputation, and the effect of microprocessor controlled knee provision

BackgroundIndividuals with unilateral transfemoral amputation walk with increased levels of asymmetry, and this is associated with reduced gait efficiency, back pain and overuse of the intact limb. This study investigated the effect of walking with a unilateral absence of loading response knee flexion on the symmetry of anterior-posterior kinetics and centre of mass accelerations. MethodsA retrospective cohort study design was used, assessing three-dimensional gait data from individuals with unilateral transfemoral amputation (n = 56). The anterior-posterior gait variables analysed included; peak ground reaction forces, impulse, centre of mass acceleration, as well as rate of vertical ground reaction force increase in early stance. With respect to these variables, this study assessed the symmetry between intact and prosthetic limbs, compared intact limbs against a healthy unimpaired control group, and evaluated effect on symmetry of microprocessor controlled knee provision. FindingsSignificant between-limb asymmetries were found between intact and prosthetic limbs across all variables (p < 0.0001). Intact limbs showed excessive loading when compared with control group limbs after speed normalisation across all variables (p < 0.0001). No improvement in kinetic symmetry following microprocessor controlled knee provision was found. InterpretationThe gait asymmetries for individuals with transfemoral amputation identified in this study suggest that more should be done by developers to address the resultant overloading of the intact limb, as this is thought to have negative long-term effects. The provision of microprocessor controlled knees did not appear to improve the asymmetries faced by individuals with transfemoral amputation, and clinicians should be aware of this when managing patient expectations.

Influence of Damping Particles on the Vibration of Spur Gear Transmission Using Numerical Modelization

The article numerically simulates the vibration reduction of a spur gear transmission by using damping particles placed in technological holes designed on the gear itself. The vibration of the gear transmission is reduced based on friction and inelastic collision which eliminates the vibrational energy by the loss during the motion of the damping particles within the technological holes. The kinematic processing of the gear system is analyzed using Adams software. The displacement acceleration data at the survey site is obtained from the Adams instrument which is valuable for evaluating the vibration level of the gear transmission. The interaction between the damping particles as well as the interaction between the particles with the gear model is simulated using EDEM software based on the discrete element method. The vibration of the gear transmission is assessed by the acceleration of the driven gear’s center of mass. The results show that the center of mass acceleration is remarkably reduced when particles are used at the rotation speed of 500 rpm and of 700 rpm. However, at the rotation speed of 1000 rpm, the vibration reduction is not much. This can be explained by the high speed and high inertia which cause the damping particles to rotate along with the gear, resulting in almost no collision between damping particles. The study also assesses the vibration reduction efficiency of the gear transmission according to the number of damping particles in each cavity and found that the number of particles accounting for 45.5% to 47.2% of the fill volume would reduce vibration most effectively. The three-millimeter diameter damper particles provide the most effective damping effect, at second place are the particles in four-millimeter diameter, and the least effective are those with two-millimeter diameter.

Using Wearables to Monitor Trunk Kinematics and Accuracy in the Sport of Axe Throwing: A Pilot Study

The sport of axe throwing has gained popularity. Axe throwing is defined as a striking sport in which competitors are required to throw an axe with accuracy and appropriate velocity. However, evidence on the role of the trunk center of mass (CoM) in axe throwing, based on in-the-field experimental settings, is lacking. The aim of this study was to understand the variation in the magnitude of trunk CoM acceleration between male and female axe throwers and its relationship to throwing accuracy. The sample consisted of 10 adult axe throwers (five males: 35.9 ± 7.5 years; five females: 25.2 ± 3.2 years) of varying skill level and experience. The axe throwers completed five single-handed overarm axe throws using their right hand. The accuracy of the axe throws was recorded, along with CoM acceleration. The overall magnitudes of trunk CoM acceleration were significantly different between the male and female axe throwers (male CoM acceleration vector: 3.6 ± 1.1; female CoM acceleration vector: 2.2 ± 0.4; p = 0.001), with males recording a higher level of accuracy (males: 76%; females: 36%) in the axe throwing task combined with greater magnitudes of vertical acceleration. Female kinematics of the trunk were observed to have significantly higher magnitudes of mediolateral acceleration (3.55 ± 1.78, p = 0.016). The overall results identified that the vector magnitude of trunk CoM acceleration was significantly correlated (r = 0.87) to performance accuracy in the male throwers. It is suggested that axe throwers should consider using trunk CoM acceleration as a viable performance metric.

Individual muscle contributions to the acceleration of the centre of mass during gait in people with mild-to-moderate hip osteoarthritis

BackgroundPeople with mild-to-moderate hip osteoarthritis (OA) exhibit hip muscle weakness, alterations in hip kinematics and kinetics and hip contact forces during gait compared to healthy controls. However, it is unclear if those with hip OA use different motor control strategies to coordinate the motion of the centre of mass (COM) during gait. Such information could provide further critical assessment of conservative management strategies implemented for people with hip OA. Research questionDo muscle contributions to the acceleration of the COM during walking differ between individuals with mild-to-moderate hip OA and controls? MethodsEleven individuals with mild-to-moderate hip OA and 10 healthy controls walked at a self-selected speed while whole-body motion and ground reaction forces were measured. Muscle forces during gait were obtained using static optimisation and an induced acceleration analysis was performed to determine individual muscle contributions to the acceleration of the COM during single-leg stance (SLS). Between-group comparisons were made using independent t-tests via Statistical Parametric Modelling. ResultsThere were no between-group differences in spatial-temporal gait parameters or three-dimensional whole-body COM acceleration. The rectus femoris, biceps femoris, iliopsoas and gastrocnemius muscles in the hip OA group contributed less to the fore-aft accelerations of the COM (p < 0.05), and more to the vertical COM acceleration with the gluteus maximus (p < 0.05), during SLS, compared to the control group. SignificanceSubtle differences exist in the way people with mild-to-moderate hip OA use their muscles to accelerate the whole-body centre of mass during the SLS phase of walking relative to healthy controls. These findings improve understanding of the complex functional consequences of hip OA and enhance our understanding of how to monitor the effectiveness of an intervention on biomechanical changes in gait in people with hip OA.

Effects of Visual Input Absence on Balance Recovery Responses to Lateral Standing Surface Perturbations in Older and Younger Adults

Although the ability to recover balance in the lateral direction has important implications with regard to fall risk in older adults, the effect of visual input on balance recovery in response to lateral perturbation and the effect of age are not well studied. We investigated the effect of visual input on balance recovery response to unpredictable lateral surface perturbations and its age-related changes. Ten younger and 10 older healthy adults were compared during balance recovery trials performed with the eyes open and eyes closed (EC). Compared with younger adults, older adults showed increased electromyography (EMG) peak amplitude of the soleus and gluteus medius, reduced EMG burst duration of the gluteus maximus and medius, and increased body sway (SD of the body's center of mass acceleration) in EC. In addition, older adults exhibited a smaller % increase (EC-eyes open) of the ankle eversion angle, hip abduction torque, EMG burst duration of the fibularis longus, and a greater % increase of body sway. All kinematics, kinetics, and EMG variables were greater in EC compared with eyes open in both groups. In conclusion, the absence of visual input negatively affects the balance recovery mechanism more in older adults compared with younger adults.

Limited Effects of Age on the Use of the Ankle and Counter-Rotation Mechanism in the Sagittal Plane

During standing the center of mass (CoM) can be controlled relative to the base of support by applying ankle moments to shift the center of pressure (CoP mechanism). An additional mechanism is the counter-rotation mechanism, i.e., changing the angular momentum of segments around the CoM to change the direction of the ground reaction force. In this study, we assessed anteroposterior balance performance and the related use of these postural control mechanisms in children, younger and older adults. Sixteen children (6-9y), 17 younger adults (18-24y) and eight older adults (65-80y) performed bipedal upright standing trials of 16 seconds on a rigid surface and on three balance boards that could freely move in the sagittal plane, varying in height (15-19 cm). Full body kinematics were measured. Performance related outcome measures, i.e., the number of trials with balance loss and the Root Mean Square of the time series of the CoM acceleration (due to the CoP and counter-rotation mechanism) and the contributions of the CoP and counter-rotation mechanism to the CoM acceleration (in %) were calculated. Furthermore, selected kinematic measures, i.e., the orientation of the board and head and the Mean Power Frequency of board orientation and of CoM acceleration were calculated. Compared to younger adults, children and older adults showed a poorer balance performance. Across age groups and conditions, the contribution of the CoP mechanism to the total CoM acceleration was dominant, i.e., 95%-108%. The contribution of the counter-rotation mechanism was limited, i.e., 19%-31% (with totals higher than 100% indicating opposite effects of both mechanisms), since the counter-rotation mechanism would conflict with stabilizing the head in space. Furthermore, children did use the counter-rotation mechanism relatively more to accelerate the CoM compared to younger adults as they are possibly still learning to limit the contribution of the counter-rotation mechanism.

In Deep Water: A Case Study on Kinematics in Deep Water Running

Introduction: This field-based case study assessed linear accelerations of the torso centre of mass (CoM) and the tibia using two wearable sensors in a triathlete performing 20 minutes of continuous deep water running. Methods: One triathlete (36 years; height; 151 cm; weight; 63 kg) participated in this field-based case study. One wearable sensor (an accelerometer) was located on the lumbar five/sacrum one (L5/S1) spinous process as a proxy for the centre of mass (CoM) and on the midpoint of the right tibia to capture linear acceleration magnitudes. The participant then performed 20 minutes of deep water running that was completed at a self-selected pace. Results: No significant differences (p&lt;0.05) in torso CoM and tibia acceleration magnitudes were detected in 20 minutes of deep water running. Despite this, the magnitude of torso CoM and tibia acceleration, notably in the anteroposterior and vertical directions, increased at the midpoint of the deep water run, possibly indicating the onset of fatigue. Conclusions: This field-based case study suggests that a wearable sensor can reliably detect variations to the torso CoM and tibia by way of linear acceleration magnitudes in 20 minutes of continuous deep water running. Based on these results, it is possible that the increased acceleration observed at the tibia were due to the onset of fatigue. Future investigations with a larger number of participants are needed to further explore the relationship between torso and tibia acceleration and fatigue in deep water running.

Motion analysis of dyadic talk during joint search and decision-making – A replication study

Human interaction frequently includes decision-making processes during which interactants call on verbal and non-verbal resources to manage the flow of interaction. In 2017, Stevanovic et al. carried out pioneering work, analyzing the unfolding of moment-by-moment dynamics by investigating the behavioral matching during search and decision-making phases. By studying the similarities in the participant's body sway during a conversation task in Finnish, the authors showed higher behavioral matching during decision phases than during search phases. The purpose of this research was to investigate the whole-body sway and its coordination during joint search and decision-making phases as a replication of the study by Stevanovic et al. (2017) but based on a German population. Overall, 12 dyads participated in this study and were asked to decide on 8 adjectives, starting with a pre-defined letter, to describe a fictional character. During this joint-decision task (duration: 206.46 ± 116.08 s), body sway of both interactants was measured using a 3D motion capture system and center of mass (COM) accelerations were computed. Matching of body sway was calculated using a windowed cross correlation (WCC) of the COM accelerations. A total of 101 search and 101 decision phases were identified for the 12 dyads. Significant higher COM accelerations (5.4*10−3 vs. 3.7*10−3 mm/s2, p < 0.001) and WCC coefficients (0.47 vs. 0.45, p = 0.043) were found during decision-making phases than during search phases. The results suggest that body sway is one of the resources humans use to communicate the arrival at a joint decision. These findings contribute to a better understanding of interpersonal coordination from a human movement science perspective.

Young adults use whole-body feedback and ankle proprioception to perceive small locomotor disturbances

To prevent a fall when a disturbance to walking is encountered requires sensory information about the disturbance to be sensed, integrated, and then used to generate an appropriate corrective motor response. Prior research has shown that feedback of whole-body motion (e.g., center-of-mass kinematics) drives this corrective response. Here, we hypothesized that young adults also use whole-body motion to perceive locomotor disturbances. 15 subjects performed a locomotor discrimination task in which the supporting leg was slowed during stance every 8–12 steps to emulate subtle slips. The perception threshold of these disturbances was determined using a psychometrics approach and found to be 0.08 ± 0.03 m/s. Whole-body feedback was examined through center-of-mass (CoM) kinematics and whole-body angular momentum (WBAM). Perturbation-induced deviations of CoM and WBAM were calculated in response to the two perturbation levels nearest each subject's perception threshold. Consistent with our hypothesis, we identified significantly higher perturbation induced deviations for perceived perturbations in sagittal-plane WBAM, anteroposterior CoM velocity, and vertical CoM velocity and acceleration. Because whole body motion is not sensed directly but instead arises from the integration of various sensory feedback signals, we also explored local sensory feedback contributions to the perception of locomotor disturbances. Local sensory feedback was estimated through kinematic analogues of vision (head angle), vestibular (head angular velocity), proprioception (i.e., sagittal hip, knee, and ankle angles), and somatosensation (i.e., anterior-posterior & mediolateral center-of-pressure, COP). We identified significantly higher perturbation induced deviations for perceived perturbations in sagittal-plane ankle angle. These results provide evidence for both whole-body feedback and ankle proprioception as important for the perception of subtle slip-like locomotor disturbances in young adults. Our interpretation is ankle proprioception is a dominant contributor to estimates of whole-body motion to perceive locomotor disturbances.

Increased muscle responses to balance perturbations in children with cerebral palsy can be explained by increased sensitivity to center of mass movement

BackgroundBalance impairments are common in children with cerebral palsy (CP). Muscle activity during perturbed standing is higher in children with CP than in typically developing (TD) children, but we know surprisingly little about how sensorimotor processes for balance control are altered in CP. Sensorimotor processing refers to how the nervous system translates incoming sensory information about body motion into motor commands to activate muscles. In healthy adults, muscle activity in response to backward support-surface translations during standing can be reconstructed by center of mass (CoM) feedback, i.e., by a linear combination of delayed (due to neural transmission times) CoM displacement, velocity, and acceleration. The level of muscle activity in relation to changes in CoM kinematics, i.e., the feedback gains, provides a metric of the sensitivity of the muscle response to CoM perturbations. Research questionCan CoM feedback explain reactive muscle activity in children with CP, yet with higher feedback gains than in TD children? MethodsWe perturbed standing balance by backward support-surface translations of different magnitudes in 20 children with CP and 20 age-matched TD children and investigated CoM feedback pathways underlying reactive muscle activity in the triceps surae and tibialis anterior. ResultsReactive muscle activity could be reconstructed by delayed feedback of CoM kinematics and hence similar sensorimotor pathways might underlie balance control in children with CP and TD children. However, sensitivities of both agonistic and antagonistic muscle activity to CoM displacement and velocity were higher in children with CP than in TD children. The increased sensitivity of balance correcting responses to CoM movement might explain the stiffer kinematic response, i.e., smaller CoM movement, observed in children with CP. SignificanceThe sensorimotor model used here provided unique insights into how CP affects neural processing underlying balance control. Sensorimotor sensitivities might be a useful metric to diagnose balance impairments.

Improving Walking Autonomy of People with Paraplegia wearing Powered Exoskeletons

Normal walking involves shifting the body's center of mass (CoM) forward in order to walk more efficiently. Unfortunately, people with paraplegia cannot voluntarily control their CoM due to their inability to move their legs or waist. Powered exoskeletons have been considered as one of the major lower limb assistive devices and developed to assist people with paraplegia to walk again. However, powered exoskeletons have limited degrees of freedom (DoFs), so they cannot fully assist with CoM control without the aid of physical therapists. Therefore, it is challenging for people with paraplegia to completely control their CoM for walking, even with the assistance of a powered exoskeleton.To address this issue, this paper focused on improving the walking autonomy of people with paraplegia wearing powered exoskeletons. Therefore, we propose a new gait pattern method that utilizes a leaning posture to effectively shift the body's CoM forward of people with paraplegia wearing powered exoskeletons. By taking advantage of the height difference between the leading and trailing leg, the proposed method facilitates the movement of the body's CoM forward during walking. To assess the efficacy of the proposed gait pattern method, the user's trunk was tilted up to 2 degrees. During the preswing phase, for every one-degree increase in the angle of the trunk tilt, the initial frontal acceleration of the user's CoM maximally rose up to 16%.

Sway and Acceleration Changes of the Center of Mass during Walking Stance Phase before and after Total Knee Arthroplasty

Elucidating the sway and changes in the acceleration of center of mass (COM) during walking is important for effective gait training and rehabilitation. The objective of this study was to verify the improvement in gait before and after total knee arthroplasty (TKA) from COM sway and the changes in the acceleration of COM during the stance phase of walking. This study included 13 patients (1 male and 12 females) with medial knee osteoarthritis who were hospitalized for TKA. The COM sway during the stance phase of walking was evaluated using root mean square (RMS) normalized by walking speed, and the changes in acceleration were further verified. Lateral and vertical RMS showed significant differences between preoperative and postoperative states and demonstrated low values after TKA. The lateral acceleration at the latter part of the early stance phase demonstrated a significant difference between preoperative and postoperative states. A significant difference was also observed in the lateral acceleration in the late stance phase between the two groups. Improvement in pain and alignment after TKA reduced the lateral sway of COM and the changes in acceleration during the gait stance phase, which is speculated to lead to improvement in gait and prevention of falls.

Contribution of lower extremity muscles to center of mass acceleration during walking: Effect of body weight

Overweight or obesity is known to be associated with altered activations of lower extremity muscles. Such changes in muscular function may lead to the development of mobility impairments or joint diseases. However, little is known about how individual lower extremity muscles contribute to the whole-body center of mass (COM) control during walking and the effect of body weight. This study examined the contribution of individual lower extremity muscle force to the COM accelerations during walking in overweight and non-overweight individuals. Musculoskeletal simulations were performed for the stance phase of walking with data collected from 11 overweight and 13 non-overweight adults to estimate lower extremity muscle forces and their contributions to the COM acceleration. Mean time-series data from each parameter were compared between body size groups using Statistical Parametric Mapping. Compared to the non-overweight group, the overweight group revealed a greater gastrocnemius contribution to the mediolateral (p = 0.006) and vertical (p < 0.001) COM accelerations during mid-stance, and had a lower vastus contribution to the anteroposterior COM acceleration (p < 0.001) during pre-swing. Increased contributions from the large posterior calf muscles to the mediolateral COM acceleration may be related to efforts to alleviate COM sway in overweight individuals.