Body Angular Momentum Research Articles

Age related differences in whole body and body part angular momentum in the frontal plane during walking

The contribution of body part angular momentum (BPAM) to whole body angular momentum (WBAM) in the frontal plane during walking differs across age groups. We investigated age related differences in BPAM and WBAM during walking. We used marker coordinate data from a publicly available database for 54 individuals aged 20–30 years and 78 aged 60–70 years. Angular momentum in the frontal plane was calculated as the sum of the translational component and the rotational component for each segment. The angular momentum of each segment was categorized into five BPAM: right and left lower limbs (foot, shank, and thigh), right and left arms (hand, forearm, and upper arm), and torso (head, thorax, and pelvis). BPAM at WBAM peak frames during stride cycles was compared between older and younger adults. The peak WBAM, angular momentum of the stance-and swing side upper limbs, and torso in older adults was significantly larger than that in younger adults, with increases of 74.6% in the stance-side upper limb, 127.5% in the swing-side upper limb, and 30.9% in the torso. These results suggest that interventions aimed at improving torso control could decrease the amplitude of WBAM in the frontal plane in older adults.

Walking balance control in different settings: Effects of walking speed and biological sex

BackgroundPrevious research has suggested that spatiotemporal step parameters differ between settings; however, it remains unclear how different settings influence walking balance control. Research questionHow do settings and sex influence walking balance control during walking at different speeds for young adults? MethodsForty-two adults (21 male (23 ± 4 years), 21 female (24 ± 5 years)) completed overground walking trials in four settings: laboratory (10 m), hallway, indoor open, and outdoor pathway (all 20 m) at three self-selected speeds (slow, preferred, fast) following verbal instructions. Participants wore 17 inertial sensors (Xsens Awinda, Movella, Henderson, NV) to capture total body kinematics. The number of included strides was matched across all conditions, with six strides included in each condition for all participants. Medial-lateral and anterior-posterior total body angular momentum range over each stride was calculated (HML range and HAP range). Setting × speed × sex mixed factorial analysis of variance with repeated measures on setting and speed were used for statistical analysis (α =.05). ResultsSignificant setting × speed interactions (p <.001) were present for both outcomes. HML range was greater in the laboratory and hallway compared to the indoor open and outdoor pathway settings for slow walking speed only. HAP range was lower in the outdoor pathway compared to all indoor settings at slow and preferred walking speeds. Differences in HAP range between settings was more pronounced at the slow speed condition. Across setting and speed conditions, HML range was greater for males compared to females. SignificanceYoung adults may alter their balance control strategy depending on the setting (laboratory, indoor open and outdoor pathway), particularly at slow speeds. Researchers and clinicians are cautioned not to assume walking in laboratory settings reflects walking in all settings nor that males and females can be examined as a single group.

A comparison of the effects of mediolateral surface and foot placement perturbations on balance control and response strategies during walking

BackgroundBalance perturbation studies during walking have improved our understanding of balance control in various destabilizing conditions. However, it is unknown to what extent balance recovery strategies can be generalized across different types of mediolateral balance perturbations. Research questionDo similar mediolateral perturbations (foot placement versus surface translation) have similar effects on balance control and corresponding balance response strategies? MethodsKinetic and kinematic data were previously collected during two separate studies, each with 15 young, healthy participants walking on an instrumented treadmill. In both studies, medial and lateral balance perturbations were applied at 80% of the gait cycle either by a treadmill surface translation or a pneumatic force applied to the swing foot. Differences in balance control (frontal plane whole body angular momentum) and balance response strategies (hip abduction moment, ankle inversion moment, center of pressure excursion and frontal plane trunk moment) between perturbed and unperturbed gait cycles were evaluated using statistical parametric mapping. ResultsBalance disruptions after foot placement perturbations were larger and sustained longer compared to surface translations. Changes in joint moment responses were also larger for the foot placement perturbations compared to the surface translation perturbations. Lateral hip, ankle, and trunk strategies were used to maintain balance after medial foot placement perturbations, while a trunk strategy was primarily used after surface translations. SignificanceSurface and foot placement perturbations influence balance control and corresponding response strategies differently. These results can help inform the development of perturbation-based balance training interventions aimed at reducing fall risk in clinical populations.

A pilot study comparing prosthetic to sound limb gait mechanics during a turning task in people with transtibial amputation

BackgroundObservational gait analysis is frequently used by clinicians to subjectively assess straight walking but is not often used to examine turning. Interlimb comparisons of phase- specific turning biomechanics in people with unilateral lower limb amputation has not previously been documented. MethodsA retrospective examination of gait kinematics and kinetics from five participants with unilateral transtibial amputation was performed. Data were collected during 90° step and spin turns capturing three distinct turning steps. Gait metrics of interest included: total turn time, stance time, peak knee flexion angle during Pre-Swing and Initial Swing gait phases, peak hip flexion and extension, ground reaction impulse, and whole body angular momentum. Statistical comparisons were made based on turn type between sound and prosthetic limbs. FindingsDuring the three turn steps (approach, apex, depart), participants spent significantly more time (P < 0.01) on their sound limb compared to their prosthetic limb regardless of turn type. Additionally, the prosthetic limb hip and knee exhibited more flexion (P < 0.05) during the apex step of turns, and whole body angular momentum was higher when the sound limb was used during the apex step of a turn (P < 0.05). InterpretationThis descriptive study offers the first phase-specific quantification of turning biomechanics in people with lower limb amputation. Results indicate that people with unilateral transtibial amputation spend more time on and experience higher impulses through their sound compared to their prosthetic limb during 90° turns, and that the prosthetic limb is performing differently than the sound limb, potentially increasing risks of injury or falls.

CARACTERÍSTICAS DO MOVIMENTO DOS MEMBROS SUPERIORES EM ATLETAS DE VOLEIBOL

ABSTRACT Introduction Passing and serving are the most direct and efficient tactics for scoring points in volleyball. The recoil of the upper limbs in dominating the ball requires strength and muscular explosion, where the effect of the body's angular momentum accompanies a joint and rhythmic action. Objective This study aims to analyze muscle strength in upper limb movements in volleyball athletes. Methods Several volleyball players volunteered for the research. The movement when the athlete hits the ball was analyzed using kinematic analysis. The relationship between muscle strength and ball movement was also analyzed. Results Body muscle tissue can be effectively trained during volleyball practice. The compound movements also help in the elasticity of the abdominal muscles. The stimulation of other muscle groups was observed in the participation of the movements. Conclusion In modern volleyball training, athletes should strengthen their training with rapid trunk muscle swing exercises to improve the coordination ability of the sets of muscle groups. The protocols presented can assist in improving players’ skills and performance. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

A simplified model for whole-body angular momentum calculation.

The capability to monitor gait stability during everyday life could provide key information to guide clinical intervention to patients with lower limb disabilities. Whole body angular momentum (Lbody) is a convenient stability indicator for wearable motion capture systems. However, Lbody is costly to estimate, because it requires monitoring all major body segment using expensive sensor elements. In this study, we developed a simplified rigid body model by merging connected body segments to reduce the number of body segments, which need to be monitored. We demonstrated that the Lbody could be estimated by a seven-segment model accurately for both people with and without lower extremity amputation.

Effects of Trunk Functional Capacity on the Control of Angular Momentum During Manual Wheelchair Braking

Background: Manual wheelchair braking induces an upper body angular impulse which must be controlled by joint moments to prevent a forward fall. Objective: The purpose of this study was to determine the effects of trunk functional capacity (low, high) on the rate of change in sagittal plane upper body angular momentum during manual wheelchair braking. Methods: Eight wheelchair users (4 low function, 4 high function) completed 10 trials of abrupt wheelchair braking. Trunk segment angles and abdominal joint angles, and normalized upper-body angular impulses were computed for each trial. Linear mixed effects models with initial velocity as a covariate were used to determine differences between groups. Results: The low function group had a higher angular impulse than the high function group with a mean difference (MD) ± SE of 1.59 ± 0.65 N∙m∙s/kg/m2, with a 95% CI 0.287 to 2.89, p = 0.018. The low function group also had a higher trunk segment extension angle, MD = –13.98 degrees, 95% CI: –26.27 to –1.69, p = .027. The low function group employed a greater trunk segment range of motion during braking when compared to the high function group, MD = 12.14 degrees, 95% CI: –24.48 to 0.21, p = 0.054. Lower trunk functional capacity wheelchair users had a higher fall risk during braking. Conclusion: Wheelchair users with less trunk function may be at increased risk of suffering a fall when bringing their wheelchair to an abrupt stop due to an impaired ability to arrest angular momentum.

Manual stabilization reveals a transient role for balance control during locomotor adaptation.

A fundamental feature of human locomotor control is the need to adapt walking patterns in response to changes in the environment. For example, when people walk on a split-belt treadmill, which has belts that move at different speeds, they adapt to the asymmetric speed constraints by reducing spatiotemporal asymmetry. Here, we aim to understand the role of balance control as a potential factor driving this adaptation process. We recruited 24 healthy, young adults to adapt to walking on a split-belt treadmill while either holding on to a handrail or walking with free arm swing. We measured whole body angular momentum and step length asymmetry as measures of dynamic balance and spatiotemporal asymmetry, respectively. To understand how changes in intersegmental coordination influenced whole body angular momentum, we also measured segmental angular momenta and the coefficient of cancellation. When participants were initially exposed to the asymmetry in belt speeds, we observed an increase in whole body angular momentum that was due to both an increase in the momentum of individual segments and a reduction in the coefficient of cancellation. Holding on to a handrail reduced the perturbation to asymmetry during the early phase of adaptation and resulted in a smaller aftereffect during early postadaptation. In addition, the stabilization provided by holding on to a handrail led to reductions in the coupling between angular momentum and asymmetry. These results suggest that regulation of dynamic balance is most important during the initial, transient phase of adaptation to walking on a split-belt treadmill.NEW & NOTEWORTHY We investigated the role of dynamic balance during adaptation to a split-belt treadmill by measuring whole body angular momentum with or without holding on to a handrail. The initial step length asymmetry and associations between balance and asymmetry reduced when holding on to a handrail during early adaptation. These findings indicate that dynamic balance mostly contributes to the initial phase of adaptation when people are exposed to an asymmetric walking constraint.

Severity of Unconstrained Simultaneous Bilateral Slips: The Impact of Frontal Plane Feet Velocities Relative to the Center of Mass to Classify Slip-Related Falls and Recoveries.

Targeted interventions to prevent slip-related falls may be informed by specific kinematic factors measured during the reactive response that accurately discriminate recoveries from falls. But reactive responses to diverse slipping conditions during unconstrained simultaneous bilateral slips, which are closely related to real-world slips, are currently unknown. It is challenging to identify these critical kinematic factors due to the wide variety of upper and lower body postural deviations that occur following the slip, which affect stability in both the sagittal and frontal planes. To explore the utility of kinematic measurements from each vertical plane to discriminate slip-related falls from recoveries, we compared the accuracy of four Linear Discriminant Analysis models informed by predetermined sagittal or frontal plane measurements from the lower body (feet velocities relative to the center of mass) or upper body (angular momentum of trunk and arms) during reactive responses after slip initiation. Unconstrained bilateral slips during over-ground walking were repeatedly administered using a wearable device to 10 younger (24.7 ± 3.2 years) and 10 older (72.4 ± 3.9 years) adults while whole-body kinematics were measured using motion capture. Falls (n = 20) and recoveries (n = 40) were classified by thresholding the dynamic tension forces measured in an overhead harness support system and verified through video observation. Frontal plane measurements of the peak feet velocities relative to the center of mass provided the best classification (classification accuracy = 73.3%), followed by sagittal plane measurements (classification accuracy = 68.3%). Measurements from the lower body resulted in higher accuracy models than those from the upper body, but the accuracy of all models was generally low compared to the null accuracy of 66.7% (i.e., predicting all trials as recoveries). Future work should investigate novel models that include potential interactions between kinematic factors. The performance of lower limb kinematics in the frontal plane in classifying slip-related falls demonstrates the importance of administering unconstrained slips and measuring kinematics outside the sagittal plane.

Recovery from sagittal-plane whole body angular momentum perturbations during walking

Healthy individuals highly regulate their whole body angular momentum (WBAM) during walking. Since WBAM regulation is essential in maintaining balance, a better understanding is required on how healthy individuals recover from WBAM perturbations. We therefore studied how healthy individuals recover WBAM in the sagittal plane. WBAM can be regulated by adjusting the moment arm of the ground reaction force (GRF) vector with respect to the whole-body centre of mass (CoM). In principle this can be done by centre of pressure (CoP) modulation and/or adjustments of the GRF direction. Two simultaneous perturbations of the same magnitude were applied in opposite direction to the pelvis and upper body (0.34m apart) to perturb WBAM but not the whole body linear momentum (WBLM), while participants walked on a treadmill. The perturbations were given at toe off right, had a magnitude of 4, 8, 12 and 16% of the participant’s body weight, and lasted for 150ms. A recovery of the WBAM was seen directly after the perturbations, induced by adapting the moment arm of the GRF with respect to the CoM. The hip joint of the stance leg played an important role in achieving the WBAM recovery. A change in the direction of the GRF vector and not a contributing CoP modulation, caused the change in moment arm. However, the change in GRF direction came from a change in the horizontal GRF, which also affects the WBLM. This suggest that regulating WBAM may take precedence over the WBLM in early recovery.

Does restricting arm motion compromise short sprint running performance?

BackgroundSynchronized arm and leg motion are characteristic of human running. Leg motion is an obvious gait requirement, but arm motion is not, and its functional contribution to running performance is not known. Because arm-leg coupling serves to reduce rotation about the body’s vertical axis, arm motion may be necessary to achieve the body positions that optimize ground force application and performance. Research questionDoes restricting arm motion compromise performance in short sprints? MethodsSprint performance was measured in 17 athletes during normal and restricted arm motion conditions. Restriction was self-imposed via arm folding across the chest with each hand on the opposite shoulder. Track and field (TF, n = 7) and team sport (TS, n = 10) athletes completed habituation and performance test sessions that included six counterbalanced 30 m sprints: three each in normal and restricted arm conditions. TS participants performed standing starts in both conditions. TF participants performed block starts with extended arms for the normal condition and elevated platform support of the elbows for the crossed-arm, restricted condition. Instantaneous velocity was measured throughout each trial using a radar device. Average sprint performance times were compared using a Repeated Measures ANOVA with Tukey post-hoc tests for the entire group and for the TF and TS subgroups. ResultsThe 30 m times were faster for normal vs. restricted arm conditions, but the between-condition difference was only 1.6% overall and < 0.10 s for the entire group (4.82 ± 0.46 s vs. 4.90 ± 0.46 s, respectively; p < 0.001) and both TF (4.55 ± 0.34 vs. 4.63 ± 0.32 s; p < 0.001) and TS subgroups (5.01 ± 0.46 vs. 5.08 ± 0.47 s; p < 0.001). SignificanceOur findings suggest that when arm motion is restricted, compensatory upper body motions can provide the rotational forces needed to offset the lower body angular momentum generated by the swinging legs. We conclude that restricting arm motion compromised short sprint running performance, but only marginally.

Recovery from Whole Body Angular Momentum Perturbations During Walking

Recovery from Whole Body Angular Momentum Perturbations During Walking

Two-Week Rehabilitation with Auditory Biofeedback Prosthesis Reduces Whole Body Angular Momentum Range during Walking in Stroke Patients with Hemiplegia: A Randomized Controlled Trial.

Walking rehabilitation is challenging in stroke patients with sensory impairments. In this study, we examined the two-week effect of an auditory biofeedback prosthesis, Auditory Foot (AF), on the change in the frontal whole body angular momentum (WBAM) range, before and after a two-week walking rehabilitation. We conducted a pilot randomized controlled trial (RCT). We employed statistical Bayesian modeling to understand the mechanism of the rehabilitation effect and predict the expected effect in new patients. The best-performing model indicated that the frontal WBAM range was reduced in the AF group by 12.9–28.7%. This suggests that the use of kinesthetic biofeedback in gait rehabilitation contributes to the suppression of frontal WBAM, resulting in an improved walking balance function in stroke patients.

Minimal centre of pressure adjustments for recovering whole body angular momentum in gait

EMG-driven modeling has been mostly used offline and on powerful desktop computers, limiting the application of this technique to neurorehabilitation settings. In this paper, we demonstrate the use of EMG-driven modeling in online (i.e. in real-time) running on a fully portable embedded system and interfaced concurrently with a powered lower limb exoskeleton. This work provides evidence of the feasibility of real-time model-based control of complex multi-joint exoskeleton system, thus opening new avenues for personalised robot-aided rehabilitation interventions.

Full attitude state reconstruction of tumbling space debris TOPEX/Poseidon via light-curve inversion with Quanta Photogrammetry

The tumbling motion of defunct satellite TOPEX/Poseidon (T/P) is governed by the μ-scale Solar Radiation Pressure (SRP) torque that spun up the satellite from the initial, nadir-pointing to the current fast spinning state [1]. In this paper, we advance the methods of Quanta Photogrammetry (QPM) in an effort to determine satellite attitude parameters – the inertial orientation of the body angular momentum vector L, the rotational phase and rate as well as the object pole coordinates with respect to L; the determined pole offset is 3.52°. The presented data support the hypothesis that the full characteristics of the satellite attitude dynamics can be obtained from a single radiant photogram measured by the photon-counting system of the Graz Satellite Laser Ranging (SLR) Observatory during an overhead pass.The analysis of the observed radiant signature of T/P gives the elevation angle of the normal vector to the solar array front surface at −1.7°, RMS = 0.63°, in the spacecraft body-centered reference frame. This information, along with the pole position, is used to model the SRP forces and torques on the satellite and determine the T/P moment of inertia I=69728,σI=75.2[kgm2], by best-fitting long-term spin simulation to the observed trend.

Unconstrained slip mechanics and stepping reactions depend on slip onset timing

Slips can occur at any time during stance. Accordingly, time-dependent tangential ground reaction forces likely produce a diverse range of slipping foot mechanics when traction is lost, thus requiring flexible recovery strategies to prevent falls. However, previous research has focused on slip onset in early stance, often with experimental anteroposterior constraints on the slipping foot, despite the diversity of environmental slips and falls. This study aimed to determine the effects of slip onset time on slip direction, severity (distance and velocity), and compensatory stepping responses. Ten young adults received slipping perturbations at different times during the stance phase of walking via a wearable device that reduces available friction while allowing the slipping foot to slide freely within the horizontal plane. Slip direction, distance, and peak velocity, compensatory step direction and distance, and upper body angular momentum magnitude and plane of rotation were derived from kinematic data. All outcome measurements significantly correlated with the time of slip onset. Slip direction and the plane of rotation of angular momentum deviated widely from the sagittal plane, exhibiting laterally-directed components exceeding those in the anteroposterior direction. As slip onset occurred later in stance, slip severity decreased while compensatory steps became longer and progressed from a posterior to anterior placement. These results provide insight into critical times within stance when slips are most severe, and into the diversity of slipping mechanics caused by changes in slip onset time.

The influence of lateral stabilization on walking performance and balance control in neurologically-intact and post-stroke individuals

BackgroundIndividuals post-stroke have an increased risk of falling, which can lead to injuries and reduced quality of life. This increased fall risk can be partially attributed to poorer balance control, which has been linked to altered post-stroke gait kinematics (e.g. an increased step width). The application of lateral stabilization to the pelvis reduces step width among neurologically-intact young and older adults, suggesting that lateral stabilization reduces the need for active frontal plane balance control. This study sought to determine if lateral stabilization is effective at improving common measures of gait performance and dynamic balance in neurologically-intact and post-stoke individuals who responded to the stabilization by reducing their step width. MethodsGait performance was assessed by foot placement and propulsion symmetry while dynamic balance was assessed by peak-to-peak range of frontal plane whole body angular momentum (HR) and pelvis and trunk sway. FindingsControls and post-stroke Responders who reduced their step width in response to stabilization also reduced their mediolateral pelvis sway, but did not exhibit changes in gait performance. Contrary to expectations, both groups exhibited an increased HR, possibly indicative of decreased balance control. This increase was the result of increased relative velocity between the pelvis and head, arms and trunk segment. InterpretationThese results suggest that a reduction in pelvis motion alone, as opposed to relative motion between the pelvis and upper body, may increase HR, decrease balance control and diminish gait performance. This finding has important implications for locomotor therapies that may seek to reduce pelvis motion.

Contradictory Postulates of Singularity

Modification of rigid body angular momentum permits controlled rotational maneuvers, and one common momentum-exchange actuator contains challenging mathematical singularities that occur when the actuator geometrically aligns perpendicularly to the commanded torque direction. Substantial research has arisen toward singularity avoidance, singularity escape (when avoidance fails), and singularity penetration which permits safe flight through regions of singularity. The latter two in particular, singularity escape and penetration require mathematical calculations of singular and near-singular quantities (very large numbers) using constituent numbers that are sometimes very small. This dichotomy leads to interesting peculiarities in some specific geometries. This short communication critically evaluates three often spoke postulates for defining singularity and the axioms that accompany the postulates. Researchers using disparate postulates arrive at contradictory conclusions about singularities, and we examine these peculiarities, leading to a few conclusions. Singular conditions must never be declared in the abstract without consideration for the commanded maneuver (e.g. the claim &amp;ldquo;the CMG system is singular&amp;rdquo;). Seeking the true angular momentum capability at near-planar skew angles, this research concludes that performance prediction is difficult installations at low skew angles should be avoided whenever permissible to enhance abilities of mathematical calculations. It will be shown that maximum momentum performance is easily predicted at very high and very low skew angles, and performance will be shown to be lowest at mid-values of skew angle. Meanwhile, maximum singularity-free performance remains elusive at even modestly low skew-angles.

Variational-Based Optimal Control of Underactuated Balancing for Dynamic Quadrupeds

This paper presents a control strategy for quadruped balancing that enables postural control in underactuated contact configurations (e.g., when standing on two point feet). Underactuated balancing has received considerable attention with prototype control models such as the cart pendulum or acrobot. Yet, when attempting to transition these solutions to balance in legged robots, technical challenges related to friction-limited contacts and the underlying manifold structure of the configuration space prevent straightforward application. This paper presents a new balance control framework that combines constrained optimal control strategies with recent variational-based linearization approaches to solve the balancing problem for a common simplified quadruped model. The controller is implemented as a convex quadratic program (QP) that uses an unconstrained optimal control solution to approximate a friction-constrained optimal policy. Unlike state-of-the-art QP-based balance controllers, the method is able to handle balance in underactuated regimes. Via comparison to model-predictive control strategies, the proposed formulation is highly compact, requiring less computation, while still showing the ability to handle extreme friction limitations. Simulation and hardware results with the MIT Mini Cheetah demonstrate the capabilities of the controller to exploit body angular momentum for disturbance recovery on two feet, and to recover from cases where the center of mass exits the support polygon. These results and the generality of the formulation suggest exploration for further application to bipeds and humanoids.

Balancing Using Vertical Center-of-Mass Motion: A 2-D Analysis From Model to Robot

Balancing strategies for humanoid robots often include the center-of-pressure control (“ankle” strategies), change of body's angular momentum (e.g., “hip” strategies), and taking a step. In this letter, we propose using vertical center-of-mass motion as an additional input for balance control. First, we specify analytic, theoretical capture regions under unilateral contact and height constraints only. Second, we add a vertical acceleration constraint and come to a simple control law for implementation. Third, we implement the control law in our momentum-based whole-body control framework. We test push recovery while standing on the NASA's Valkyrie humanoid robot and compare with a constant height controller, and we show that recovery can be improved using vertical motion. Furthermore, we discuss the differences that can be observed after the application of a simple model on a robot.