Mediolateral Center Of Mass Displacement Research Articles

Evaluation of Skipping in College Students with and without Autism Spectrum Disorder.

Children with Autism Spectrum Disorder (ASD) demonstrate motor skill deficits in comparison to their neurotypically developing peers. However, it is unknown whether these motor skill deficits persist into adulthood. We evaluated skipping kinematics and motor performance in college students with and without ASD. We collected kinematic data from 20 college students, 10 with ASD and 10 without ASD, using a 12-camera three-dimensional motion capture system while participants completed three skipping trials. We scored skipping performance using Everyone Can! and the Halverson Developmental Sequences for Skipping, and we processed data using Cortex, Visual 3D, and MATLAB. We extracted data for center of mass excursion, peak velocity of joint extension, and peak joint angles of the hip, knee, and ankle of the dominant leg. Independent t-tests and Mann-Whitney U tests were used to examine differences between groups with an alpha level of p 0.05. We found no statistically significant differences for peak sagittal plane joint angles, velocities, or vertical center of mass excursion. However, the ASD group demonstrated greater medio-lateral center of mass displacement (ASD M = .08, SD = .1m; Control M = .03, S = .03m; p = .026) and greater frontal plane knee excursion (ASD M = 11.49, SD = 6.23°; Control M = 5.29, SD = 2.44°; p = .01) than participants without ASD. Similarly, the ASD group performed less proficiently in skipping than the group without ASD, as assessed by the developmental scoring methods (Everyone Can! composite score medians [interquartile range]: ASD M = 10.5, SD = 8; Control M = 15.0, SD = 0, p = .008). Despite many similarities in skipping kinematics between groups, participants with ASD were less proficient in skip performance than participants without ASD. Interventions for individuals with ASD addressing skipping proficiency or the performance of other locomotor skills, such as running and jumping, may promote participation in activities that involve complex motor skills and help individuals with ASD lead more physically active lives.

Comparison of ground reaction force and marker-based methods to estimate mediolateral center of mass displacement and margins of stability during walking

Dynamic balance control during human walking can be described by the distance between the mediolateral (ML) extrapolated center of mass (XCoM) position and the base of support, the margin of stability (MoS). The ML center of mass (CoM) position during treadmill walking can be estimated based on kinematic data (marker-based method) and a combination of ground reaction forces and center of pressure positions (GRF-based method). Here, we compare a GRF-based method with a full-body marker-based method for estimating the ML CoM, ML XCoM and ML MoS. Fifteen healthy adults walked on a dual-belt treadmill at comfortable walking speed for three minutes. Kinetic and kinematic data were collected and analyzed using a GRF-based and marker-based method to compare the ML CoM, ML XCoM and ML MoS. High correlation coefficients (r > 0.98) and small differences (Root Mean Square Difference < 0.0072 m) in ML CoM and ML XCoM were found between the GRF-based and marker-based methods. The GRF-based method resulted in larger ML XCoM excursion (0.0118 ± 0.0074 m) and smaller ML MoS values (0.0062 ± 0.0028 m) than the marker-based method, but these differences were consistent across participants. In conclusion, the GRF-based method is a valid method to determine the ML CoM, XCoM and MoS. One should be aware of higher ML XCoM and smaller ML MoS values in the GRF-based method when comparing absolute values between studies. The GRF-based method strongly reduces measurement times and can be used to provide real-time CoM-CoP feedback during treadmill gait training.

Evaluation Of Skipping In College Students With And Without Autism Spectrum Disorder

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder that affects social interactions and behaviors. Children with ASD demonstrate motor skill deficits in comparison to their neurotypically developing peers. However, it is unknown whether these motor skill deficits translate into adulthood. PURPOSE: Skipping performance and kinematics were evaluated in college students with and without ASD. METHODS: 20 college students, 10 with ASD and 10 without, participated in this study. Following a demonstration, each participant completed three skipping trials. Data was collected using a three-dimensional 12-camera motion capture system at 120 Hz using retro-reflective markers that were placed on the participants’ upper and lower extremities. Developmental scoring of skipping performance was performed using a combination of Everyone Can! and the Halverson Developmental Sequences for Skipping. Data were processed using Cortex, Visual 3D, Matlab, and SPSS software. Center of mass excursion, the peak velocity of joint extension, and peak joint angles of the hip, knee, and ankle of the dominant leg were extracted. Independent t-tests were used to compare normally distributed kinematic variables and Mann-Whitney U test were used to examine the center of mass excursion and developmental scores between groups with an alpha level of 0.05. RESULTS: Individuals with ASD performed less proficiently in skipping than individuals without ASD as assessed by the developmental scoring (Everyone Can! composite score median (interquartile range): ASD: 10.5(8), Control: 15.0(0), p = 0.008). However, there were no statistically significant differences for the peak joint angles, velocities, or vertical center of mass excursion. The ASD group demonstrated greater medio-lateral center of mass displacement (ASD 0.08(0.1) m; Control 0.03(0.03) m; p = 0.026). CONCLUSION: Participants with ASD were less proficient in their skip performance in comparison to participants without ASD. Given that skipping is a motor skill used in many common sports and leisure activities, interventions addressing the ability to skip proficiently may promote participation in these activities and help individuals with ASD lead more physically active lives.

Gait balance control after fatigue: Effects of age and cognitive demand

BackgroundFatigue is a commonly mentioned symptom in older adults, and walking under the influence of fatigue frequently occurs in daily activities. Studies have reported individual effects from fatigue or cognitive demand on gait performance. However, the information on how fatigue and cognitive demand interact to affect gait balance control is still lacking. Research QuestionHow does fatigue affect walking balance control in young and older adults with and without performing a concurrent cognitive task? MethodsWe collected and analyzed motion data from 17 young and 17 older adults, who performed over-ground walking with and without a concurrent working memory test, before and after been fatigued by performing repetitive sit-to-stand movements. Three-way ANOVAs were used for statistical analysis with Age (young and older adults), Fatigue (pre- and post-fatigue), and Task (single-task and dual-task) as factors. ResultsFrom pre- to post-fatigue, an increased gait velocity was observed during dual-task walking regardless of age (p = .02). Only young adults demonstrated a significant increase in mediolateral center of mass displacement (M-L CoM) at post-fatigue (p = .019). Accuracies of the working memory test were not affected by Age, Task, or Fatigue. SignificanceOur findings revealed that gait balance control, as measured by the M-L CoM, deteriorated post-fatigue in young adults. Older adults maintained their mediolateral body sway from pre-fatigue to post-fatigue. Fatigue effects were not further exacerbated during dual-task walking, and similar cognitive performance was maintained as performance fatigability increased.

Research on Knee Joint Load and Influencing Factors of Typical Tai Chi Movements.

Background Tai chi is recognized worldwide for its rehabilitation abilities and healthcare benefits. However, in recent years, some movements associated with tai chi have been shown to damage the lower limb joints. The purpose of this study was to investigate and compare the effects of different movements, postures, center of mass (COM) movements, and range of knee movement of tai chi exercises on knee joint load. Methods Fourteen professional tai chi practitioners in two postures (high and low) were enrolled to perform the following four typical tai chi movements: wild horse's mane (WHM), repulse monkey (RM), wave-hand in cloud (WHIC), and grasp the bird's tail (GBT). Kinematic and kinetics data were synchronously collected using the Vicon infrared high-speed motion capture system and a three-dimensional (3D) force measurement platform. Variance analysis and partial correlation analysis were performed to investigate factors influencing peak knee joint moment and vertical ground reaction force (VGRF). Results The results showed that the peak knee extension and abduction moment were larger in WHM and RM than those in WHIC and GBT (p < 0.05). WHM was associated with greater rotation moment than the other typical movements (p < 0.05). VGRF and joint moment among different poses were significantly different. Low-pose tai chi typical movements were associated with greater VGRF, knee joint extension and abduction, and rotation moments than high-pose movements (p < 0.05). The anteroposterior and mediolateral COM displacements were strongly and positively associated with VGRF (p < 0.001), while the mediolateral COM displacement was negatively associated with knee extension moment (p < 0.001). The knee internal-external rotation ROM and anteroposterior and mediolateral COM displacements were positively associated with knee abduction moment (p < 0.01). Conclusion For long-term tai chi exercises, choosing a suitable posture based on an individual exercise level and reasonable control of knee ROM and COM displacement can reduce the risk of knee injury during exercise.

Abnormal Gait Movements Prior to a Near Fall in Individuals After Stroke

ObjectiveTo investigate the abnormal kinematic and kinetic movements in the last gait cycle before a near fall in individuals poststroke, where a near fall is defined as a physical therapist feeling the need to stabilize a patient. DesignRetrospective study. SettingA rehabilitation center. ParticipantsTwenty-five adults (22 men, 3 women; N=25) with an average age of 66.3 years and mean duration from stroke of 4 months who required manual assistance for a sudden imbalance during routine 3-dimensional motion analysis. InterventionsNot applicable. Main Outcome MeasuresWe compared the averaged usual gait cycle and the last cycle before the near-falling gait cycle (pre–near-falling gait cycle). We obtained the following spatiotemporal parameters: gait velocity, gait cycle duration, mediolateral center of mass displacement, step length, step width, joint moments, and angular displacement of the trunk in a cycle. Peak values of joint moments and trunk angle displacement were calculated. ResultsEtiology for near falls included toe trip, mediolateral perturbation, and knee collapse. We found the following significant differences in the pre–near-falling gait cycle compared with the usual gait cycle: decreased gait velocity, prolonged total cycle time, and excessive mediolateral center of mass displacement. ConclusionsDecreased gait velocity, prolonged cycle time, and excessive mediolateral center of mass displacement may be a sign of an impending fall in people with impaired gait after stroke.

Spatiotemporal and Kinematic Comparisons Between Anthropometrically Paired Male and Female Soldiers While Walking With Heavy Loads.

Limited work comparing the effect of heavier carried loads (greater than 30 kg) between men and women has attributed observed differences to sex with the possibility that anthropometric differences may have contributed to those discrepancies. With the recent decision permitting women to enter Combat Arms roles, knowledge of sex-based differences in gait response to load carriage is more operationally relevant, as military loads are absolute and not relative to body weight. The purpose of this study was to describe differences in gait parameters at light to heavy loads between anthropometrically similar male and female soldiers. Eight female and 8 male soldiers, frequency-matched (1-to-1) on height (±0.54 cm) and mass (±0.52 kg), walked at 1.34 m∙s-1 for 10-min bouts on a level treadmill while unloaded (BM) and then carrying randomized vest-borne loads of 15, 35, and 55 kg. Spatiotemporal and kinematic data were collected for 30 s after 5 min. Two-way repeated measures analyses of variance were conducted to compare the gait parameter variables between sexes at each load. As load increased, overall, the percent double support increased, step frequency increased, stride length decreased, hip and ankle range of motion (ROM) increased, and vertical center of mass (COM) displacement increased. Sex-based significant differences were observed in knee ROM and mediolateral COM displacement. Among the male participants, knee ROM increased significantly for all loads greater than BM. For mediolateral COM displacement, male remained constant as load increased, whereas female values decreased between BM and 35 kg. Spatiotemporal and kinematic differences in gait parameters were primarily because of increases in load magnitude. The observed sex-related differences with increasing loads suggest that women may require a more stable gait to support the additional load carried.

Fear Priming: A Method for Examining Postural Strategies Associated With Fear of Falling.

Fear of falling influences postural strategies used for balance, and is key in the maintenance of independent living and quality of life as adults age. However, there is a distinct need for methodology that aims to specifically address and prime fear under dynamic conditions, and to better determine the role of fear in movement preparation. This preliminary study investigated how fear priming influences fear of falling in young and older individuals, and assessed how changes in fear of falling map to movement behavior. Young (21.5 ± 1.7 years, n = 10) and older (58.1 ± 2.2 years) participants matched for height, weight, and sex were repeatedly exposed to four different and incrementally challenging laboratory-based slipping perturbations during a self-initiated, goal-directed step and reach task. Both younger and older cohorts showed similar heightened perceptions in fear of falling after fear priming, and changes in peak joint excursions including reduced ankle flexion, and increased lumbar flexion after fear priming. Age-related changes were only evident in total mediolateral center of mass displacement, with younger participants showing greater displacement after fear priming. Despite clear differences in preparatory muscle onsets relative to reach onset seen in older participants, muscle timings or co-contraction indices were not significantly different. Methods utilizing repeated exposure to varying increases of a slip-based postural challenge can successfully prime fear of falling in individuals, regardless of age.

Motor adjustments during time-constrained sit-to-walk in people with Parkinson's disease

Sit-to-walk (STW) is a sequential task and a merge of sit-to-stand (STS) and gait initiation that are impaired in people with Parkinson's disease (PD). Performing sequential task under time constraint (e.g., stand up and walk to answer an urgent call) might influence people with PD due to their deficits on internal regulation of continuous, rhythmic and fast movements. It is known the PD behavior during STS and gait initiation tasks are impaired, however, little is known regarding PD behavior on STW. Thus, the aim of this study was to assess the motor behavior of people with PD and healthy older adults during the STW task under time constraint. Fourteen people with idiopathic PD and 14 healthy older adults (OA) participated in this study. They performed the STW task under a time constraint. STW performance (STW total duration, duration of each of the 4 phases of the STW, and the drop in the center of mass (COM) momentum, identified as Fluidity Index - FI), kinematics and kinetics outcomes were assessed throughout the task. The PD group showed increased STW total time and lower FI, longer seat-off (Phase 1) time and first step (Phase 4) when compared to the OA group. Furthermore, the PD group showed more motor impairments (kinematics and kinetics) than the OA group throughout the task from seat-off until heel-off. Also, people with PD exhibited larger mediolateral COM displacement in the standing phase (Phase 2) and greater ground reaction force (GRF) in Phases 1 and 3. We observed that people with PD exhibited more restrictions when compared with healthy older adults on their STW performance, COM and GRF parameters during the STW under time constraint. Some clinical impairments usually observed in people with PD might explain their STW performance such as, motor planning deficits, less automatic motor control and mediolateral balance impairments.

Trunk lean gait decreases multi-segmental coordination in the vertical direction.

[Purpose] The strategy of trunk lean gait to reduce external knee adduction moment (KAM) may affect multi-segmental synergy control of center of mass (COM) displacement. Uncontrolled manifold (UCM) analysis is an evaluation index to understand motor variability. The purpose of this study was to investigate how motor variability is affected by using UCM analysis on adjustment of the trunk lean angle. [Subjects and Methods] Fifteen healthy young adults walked at their preferred speed under two conditions: normal and trunk lean gait. UCM analysis was performed with respect to the COM displacement during the stance phase. The KAM data were analyzed at the points of the first KAM peak during the stance phase. [Results] The KAM during trunk lean gait was smaller than during normal gait. Despite a greater segmental configuration variance with respect to mediolateral COM displacement during trunk lean gait, the synergy index was not significantly different between the two conditions. The synergy index with respect to vertical COM displacement during trunk lean gait was smaller than that during normal gait. [Conclusion] These results suggest that trunk lean gait is effective in reducing KAM; however, it may decrease multi-segmental movement coordination of COM control in the vertical direction.

Effects of Alexander Technique training experience on gait behavior in older adults

Heightened fall risk, potentially caused by aging-related changes in gait, is a serious health issue faced by older adults. The Alexander Technique is thought to improve balance and motor function; however, the technique's effect on gait has not been studied. The purpose of this study was to examine the effect of Alexander Technique training in older adults on the temporospatial characteristics of gait and medio-lateral center of mass displacement during fast and comfortably paced over-ground walking. Six licensed Alexander Technique teachers and seven controls between the ages of 60 and 75 years of age participated in the study. Alexander Technique teachers exhibited a reduction in medio-lateral center of mass displacement during fast paced walking compared to comfortably paced walking that was not present in controls. Due to this difference Alexander Technique teachers displayed a smaller medio-lateral Center of Mass displacement compared to controls during fast paced walking. Alexander Technique teachers also demonstrated significantly smaller stride width and lower gait timing variability compared to controls. These findings, which suggest superior control of dynamic stability during gait and potentially reduced fall risk in Alexander Technique teachers, warrant further study.

A neuromechanical strategy for mediolateral foot placement in walking humans.

Stability is an important concern during human walking and can limit mobility in clinical populations. Mediolateral stability can be efficiently controlled through appropriate foot placement, although the underlying neuromechanical strategy is unclear. We hypothesized that humans control mediolateral foot placement through swing leg muscle activity, basing this control on the mechanical state of the contralateral stance leg. Participants walked under Unperturbed and Perturbed conditions, in which foot placement was intermittently perturbed by moving the right leg medially or laterally during the swing phase (by ∼50-100 mm). We quantified mediolateral foot placement, electromyographic activity of frontal-plane hip muscles, and stance leg mechanical state. During Unperturbed walking, greater swing-phase gluteus medius (GM) activity was associated with more lateral foot placement. Increases in GM activity were most strongly predicted by increased mediolateral displacement between the center of mass (CoM) and the contralateral stance foot. The Perturbed walking results indicated a causal relationship between stance leg mechanics and swing-phase GM activity. Perturbations that reduced the mediolateral CoM displacement from the stance foot caused reductions in swing-phase GM activity and more medial foot placement. Conversely, increases in mediolateral CoM displacement caused increased swing-phase GM activity and more lateral foot placement. Under both Unperturbed and Perturbed conditions, humans controlled their mediolateral foot placement by modulating swing-phase muscle activity in response to the mechanical state of the contralateral leg. This strategy may be disrupted in clinical populations with a reduced ability to modulate muscle activity or sense their body's mechanical state.

Coordination of Dynamic Balance During Gait Training in People With Acquired Brain Injury

Clark RA, Williams G, Fini N, Moore L, Bryant AL. Coordination of dynamic balance during gait training in people with acquired brain injury. ObjectiveTo investigate movement of the center of mass (COM) during different gait training methods in people with neurologic conditions. DesignCoordination of the gait cycle, represented by mediolateral COM displacement amplitude, timing, and stability, was assessed during a variety of gait training methods performed in a single session. SettingGait laboratory. ParticipantsPeople who were unable to walk unassisted due to an acquired brain injury (n=17) and healthy control subjects (n=25). InterventionsThe participants performed 7 alternative gait training methods in a randomized order. These were therapist manual facilitation, the use of a gait assistive device, treadmill walking with handrail support, and 4 variations of body weight–support treadmill training with combinations of handrail and/or therapist support. Main Outcome MeasuresMediolateral COM movement was analyzed in terms of displacement amplitude (overall range of motion), timing (relative to stride time), and stability (steadiness of the movement). Normative values for these measures were acquired from 25 healthy participants walking at a self-selected comfortable pace. ResultsBody weight–support treadmill training without any additional support resulted in significantly (P<.05) greater amplitude, altered timing, and reduced movement stability compared with nonpathologic gait. Allowing handrail support or therapist facilitation reduced this effect and resulted in treadmill training (± body weight support) having lower movement amplitudes when compared with the other training methods. Therapist manual facilitation most closely matched nonpathologic gait for timing and stability. ConclusionsIn the context of overall dynamic gait coordination, no single method of training provides the optimal stimulus. A training program that uses a variety of techniques may provide a beneficial rehabilitation response.

Do mechanical gait parameters explain the higher metabolic cost of walking in obese adolescents?

Net metabolic cost of walking normalized by body mass (C(W.BM(-1)); in J.kg(-1).m(-1)) is greater in obese than in normal-weight individuals, and biomechanical differences could be responsible for this greater net metabolic cost. We hypothesized that, in obese individuals, greater mediolateral body center of mass (COM) displacement and lower recovery of mechanical energy could induce an increase in the external mechanical work required to lift and accelerate the COM and thus in net C(W.BM(-1)). Body composition and standing metabolic rate were measured in 23 obese and 10 normal-weight adolescents. Metabolic and mechanical energy costs were assessed while walking along an outdoor track at four speeds (0.75-1.50 m/s). Three-dimensional COM accelerations were measured by means of a tri-axial accelerometer and gyroscope and integrated twice to obtain COM velocities, displacements, and fluctuations in potential and kinetic energies. Last, external mechanical work (J.kg(-1).m(-1)), mediolateral COM displacement, and the mechanical energy recovery of the inverted pendulum were calculated. Net C(W.BM(-1)) was 25% higher in obese than in normal-weight subjects on average across speeds, and net C(W.BM(-67)) (J.kg(-0.67).m(-1)) was significantly related to percent body fat (r(2) = 0.46). However, recovery of mechanical energy and the external work performed (J.kg(-1).m(-1)) were similar in the two groups. The mediolateral displacement was greater in obese subjects and significantly related to percent body fat (r(2) = 0.64). The mediolateral COM displacement, likely due to greater step width, was significantly related to net C(W.BM(-67)) (r(2) = 0.49). In conclusion, we speculate that the greater net C(W.BM(-67)) in obese subjects may be partially explained by the greater step-to-step transition costs associated with wide gait during walking.

The effect of walking speed on center of mass displacement

The movement of the center of mass (COM) during human walking has been hypothesized to follow a sinusoidal pattern in the vertical and mediolateral directions. The vertical COM displacement has been shown to increase with velocity, but little is known about the mediolateral movement of the COM. In our evaluation of the mediolateral COM displacement at several walking speeds, 10 normal subjects walked at their self-selected speed and then at 0.7, 1.0, 1.2, and 1.6 m/s in random order. We calculated COM location from a 15-segment, full-body kinematic model using segmental analysis. Mediolateral COM displacement was 6.99 +/- 1.34 cm at the slowest walking speed and decreased to 3.85 +/- 1.41 cm at the fastest speed (p < 0.05). Vertical COM excursion increased from 2.74 +/- 0.52 at the slowest speed to 4.83 +/- 0.92 at the fastest speed (p < 0.05). The data suggest that the relationship between the vertical and mediolateral COM excursions changes substantially with walking speed. Clinicians who use observational gait analysis to assess walking problems should be aware that even normal individuals show significant mediolateral COM displacement at slow speeds. Excessive vertical COM displacement that is obvious at moderate walking speeds may be masked at slow walking speeds.