Limb Velocity Research Articles

Human micro-doppler detection and classification studies at Mersin University using real outdoor experiments via C-band FMCW radar

In this work, a unique radar hardware is introduced for human-gait micro-Doppler studies. The developed radar sensor operates in C-band microwave frequencies. We share several outdoor experiments at Mersin University facilities to detect and characterize human walking and running movements. In these experiments, various walking and running movements were performed with different people. To examine the Doppler properties of human motion, raw data gathered is transformed onto 2D joint-time-frequency plane. The generation of micro-Doppler signatures in the transformed data is the first step in the extraction of features of the walking/running human motion. It is shown that the directions, durations, range distances as well as torso and limb velocities of walking and running human movements in each experiment are successfully obtained from these micro-Doppler signatures.

The Impact of Limb Velocity Variability on Mallet Accuracy in Marimba Performance

The present study examined spatial accuracy of mallet endpoints in a marimba performance context. Trained percussionists performed two- (i.e., Experiment 1) and four-mallet (i.e., Experiment 2) excerpts in three tempo conditions including slow, intermediate, and fast. Motion capture was utilized to gather data of upper-limb and mallet movements, as well as to compute velocities of the upper-limb joints. Mallet spatial accuracy was assessed by comparing mallet endpoints to a visual target positioned on the marimba. It was hypothesized that mallet spatial accuracy would be reduced as tempo condition increased, with effects on joint kinematics potentially revealing sensorimotor mechanisms underlying optimal sound production in marimba. Across both experiments, mallet accuracy was reduced as tempo condition increased. Interestingly, velocity variability in the elbows, wrists, and hands increased as mallet accuracy decreased. Such a pattern of effects suggested that sound production in marimba is suboptimal at fast relative to slow tempi. In addition, the velocity variability effects highlight the impact of motor planning mechanisms on sound production. Overall, the results shed new light on sensorimotor control in percussion which can be leveraged to enhance the training of percussionists.

Effect of velocity and acceleration in joint angle estimation for an EMG-Based upper-limb exoskeleton control

Most studies on estimating user's joint angles to control upper-limb exoskeleton have focused on using surface electromyogram (sEMG) signals. However, the variations in limb velocity and acceleration can affect the sEMG data and decrease the angle estimation performance in the practical use of the exoskeleton. This paper demonstrated that the variations in elbow angular velocity (EAV) and elbow angular acceleration (EAA) associated with normal use led to a large effect on the elbow joint angle estimation. To minimize this effect, we proposed two methods: (1) collecting sEMG data of multiple EAVs and EAAs as training data and (2) measuring the values of EAV and EAA with a gyroscope. A self-developed upper-limb exoskeleton with pneumatic muscles was used in the online control phase to verify our methods' effectiveness. The predicted elbow angle from the sEMG-angle models which were trained in the offline estimation phase was transferred to control signal of the pneumatic muscles to actuate the exoskeleton to move to the same angle. In the offline estimation phase, the average root mean square error (RMSE) between predicted elbow angle and actual elbow angle was reduced from 22.54° to 10.01° (using method one) and to 6.45° (using method two), respectively; in the online control phase, method two achieved a best control performance (average RMSE = 6.87°). The results showed that using multi-sensor fusion (sEMG sensors and gyroscope) achieved a better estimation performance than using only sEMG sensor, which was helpful to eliminate the velocity and acceleration effect in real-time joint angle estimation for upper-limb exoskeleton control.

Sliding mode control for offshore parallel antenna platform with large orientation workspace

A novel sliding mode control strategy is proposed to solve the trajectory tracking control problem of an offshore antenna platform, which uses a Stewart-type parallel mechanism and has a large orientation workspace. To obtain comprehensive posture parameters of the offshore antenna platform, a posture compensation algorithm using the information of azimuth and elevation is proposed. Considering known limb lengths, a state observer which based on a super-twisting algorithm is presented to obtain limb velocities. To solve the trajectory-tracking control problem of the platform, a modified nonsingular terminal integral sliding mode controller is proposed. To reduce chattering, the sliding mode controller is equipped with a higher order super-twisting algorithm. The Lyapunov theory was used to prove its stability. Simulation results on a large-orientation workspace offshore antenna platform demonstrate its superiority over three other controllers. Compared with the traditional sliding mode controller with super-twisting algorithm, the integral of the squared error of the proposed control strategy is 49.49% lower.

Hamstring Torque, Velocity and Power Elastic Band Measurements during Hip Extension and Knee Flexion

The quantitative dynamic monitoring of the performance of hamstring muscles during rehabilitation and training cannot currently be undertaken using elastic resistance bands. Hip extension with a fully extended knee involves hamstring agonists, while knee flexion involves only the hamstring. The purpose of this study is to provide normative values of torque, velocity and power involving hamstring muscles opposing elastic bands. Twenty amateur athletes aged 25.7 ± 4.9, were studied during two motor tasks—hip extension and knee flexion, both isometric & dynamic—with an elastic resistance band and DINABANG portable instrument. We compared the peak isometric torque in hip extension with agonists (2.93 Nm/kg) and without them (1.21 Nm/kg): the difference is significant. The peak angular limb velocity—starting at 50% of the maximum torque—is smaller in hip extension with agonists (215.96°/s) than in a knee flexion without them (452.56°/s). The combination of peak torque and peak velocity estimates power and there is no difference (p = 0.051) with and without agonists: 452.56°Nm/s.kg without agonists and 542.13°Nm/s.kg with them. This study opens the possibility of monitoring torque–velocity–power profiles for hamstring exercise in open chain.

Isometric and Anisometric Contraction Relationships with Surface Electromyography.

The isometric contraction is the most investigated muscle contraction, however most tasks in daily life involve anisometric contractions. Most hand prostheses studies [1] use sEMG features to directly relate the exerted force as a means of intuitive control. It may thus be expected that similar sEMG-velocity relationships characterizing anisometric contractions may also contribute towards intuitive prosthetic hand control. While different contraction type relationships have been studied separately, in this work anisometric and isometric contraction experiments on the biceps brachii muscle were carried out using the same sEMG electrode system and the motor unit activity was then related to limb velocities and limb forces, to respectively characterize the isometric and anisometric contractions. This muscle was chosen as a simpler alternative to the synergistic hand muscles as an initial test of the general concept.Clinical Relevance- These contraction characterizations with sEMG may be used to afford prosthetic intuitive control and to assist in motor impairment diagnosis and rehabilitation.

Contribution of Retinal Motion to the Impulse Control of Target-Directed Aiming

Abstract Contemporary models of sensorimotor control contend that visually regulated movement adjustments may unfold early during a target-directed limb movement through an impulse control process that makes use of anticipatory forward models. To date, evidence surrounding impulse control has involved adjustments to a purported misperception in limb velocity following the unexpected onset of a moving background. That is, the limb is perceived to move faster and undershoots more when there is an incongruent moving background and vice versa. However, this particular behavior may manifest from an independent oculo-manual-following response. The present study aimed to deconstruct these proposals and, with them, the processes that underlie impulse control. Participants had to rapidly reach upward to land their index finger accurately on a target. On 33% of trials, the background, over which the movement was made, moved either up, down, right, or left. Displacements in the primary and perpendicular directions of movement showed spatial trajectories that were consistent with the directions of the moving backgrounds. This behavior was most prevalent in measurements taken at the movements’ peak negative acceleration and endpoints. Moreover, analysis of standardized displacements in the moving background conditions indicated no significant differences in the extent of the movements toward each of the moving backgrounds. These findings indicate that movement adjustments can manifest from an oculo-manual-following response rather than a misperception of limb velocity. We suggest that the anticipatory forward model that comprises impulse control may incorporate features of the environment that surround the vicinity of the limb.

Analysis of Whole-Body Coordination Patterning in Successful and Faulty Spikes Using Self-Organising Map-Based Cluster Analysis: A Secondary Analysis.

This study investigated the whole-body coordination patterning in successful and faulty spikes using self-organising map-based cluster analysis. Ten young, elite volleyball players (aged 15.5 ± 0.7 years) performed 60 volleyball spikes in a real-game environment. Adopting the cluster analysis, based on a self-organising map, whole-body coordination patterning was explored between successful and faulty spikes of individual players. The self-organising maps (SOMs) portrayed whole body, lower and upper limb coordination dissimilarities during the jump phase and the ball impact phases between the successful and faulty spikes. The cluster analysis illustrated that the whole body, upper limb and lower limb coordination patterning of each individual’s successful spikes were similar to their faulty spikes. Range of motion patterning also demonstrated no differences in kinematics between spike outcomes. Further, the upper limb angular velocity patterning of the players’ successful/faulty spikes were similar. The SPM analysis portrayed significant differences between the normalized upper limb angular velocities from 35% to 45% and from 76% to 100% of the spike movement. Although the lower limb angular velocities are vital for achieving higher jumps in volleyball spikes, the results of this study portrayed that the upper limb angular velocities distinguish the differences between successful and faulty spikes among the attackers. This confirms the fact that volleyball coaches should shift their focus toward the upper limb velocity and coordination training for higher success rates in spiking for volleyball attackers.

Absent phasing of respiratory and locomotor rhythms in running mice.

Examining whether and how the rhythms of limb and breathing movements interact is highly informative about the mechanistic origin of hyperpnoea during running exercise. However, studies have failed to reveal regularities. In particular, whether breathing frequency is inherently proportional to limb velocity and imposed by a synchronization of breaths to strides is still unclear. Here, we examined respiratory changes during running in the resourceful mouse model. We show that, for a wide range of trotting speeds on a treadmill, respiratory rate increases to a fixed and stable value irrespective of trotting velocities. Respiratory rate was yet further increased during escape-like running and most particularly at gallop. However, we found no temporal coordination of breaths to strides at any speed, intensity, or gait. Our work thus highlights that exercise hyperpnoea can operate, at least in mice and in the presently examined running regimes, without phasic constraints from limb movements.

A influência da composição corporal na capacidade motora de ingressantes do curso de Educação Física

Introdução: A entrada na universidade é um marco na mudança de comportamento dos jovens. As mudanças que ocorrem na fase da formação inicial são determinantes para uma vida adulta saudável. Mundialmente, os altos índices de obesidade e os baixos níveis de atividade física são preocupantes, estes que associam com a coordenação, que é preditora de continuidade da prática motora. Objetivo: Analisar a influência da composição corporal na capacidade motora de ingressantes nos cursos de Educação Física. Métodos: Participaram do estudo 137 universitários (21,8±3,6 anos), de ambos os sexos. A composição corporal (índice de massa corporal, percentual de gordura, relação cintura/quadril), coordenação motora sem e com bola (KTK, TECOBOL-curto), e testes de aptidão física (PROESP-br) foram analisados por meio de estatística descritiva, teste t-student e Correlação de Pearson, adotando-se p≤0,05. Resultados: Comparações entre os sexos revelaram diferenças significativas (p≤0,05) nos testes físicos e motores, exceto nos testes de sentar e alcançar e trave de equilíbrio. Houve correlações significativas entre a composição corporal, os testes físicos e motores. O percentual de gordura apresentou correlação com os testes de aptidão cardiorrespiratória (r=-0,769; p≤0,001), força de membros inferiores (r=-0,710; p≤0,001), força de membros superiores (r=-0,604; p≤0,001), velocidade (r=0,672; p≤0,001) e drible do TECOBOL (r=0,502; p≤0,001). Conclusão: Os resultados indicam que as capacidades motoras estão relacionadas com os indicadores da composição corporal em jovens ingressantes no curso de Educação Física.

Fall Detection Based on Dual-Channel Feature Integration

Falls have caught great harm to the elderly living alone at home. This paper presents a novel visual-based fall detection approach by Dual-Channel Feature Integration. The proposed approach divides the fall event into two parts: falling-state and fallen-state, which describes the fall events from dynamic and static perspectives. Firstly, the object detection model (Yolo) and the human posture detection model (OpenPose) are used for preprocessing to obtain key points and the position information of a human body. Then, a dual-channel sliding window model is designed to extract the dynamic features of the human body (centroid speed, upper limb velocity) and static features (human external ellipse). After that, MLP (Multilayer Perceptron) and Random Forest are applied to classify the dynamic and static feature data separately. Finally, the classification results are combined for fall detection. Experimental results show that the proposed approach achieves an accuracy of 97.33% and 96.91% when tested with UR Fall Detection Dataset and Le2i Fall Detection Dataset.

A Method to Extract Motion Velocities of Limb and Trunk in Human Locomotion

Human motion monitoring is important in applications of movies, animation, sport training, physical rehabilitation, and human-robot interaction. There is a demand for a simple and easy-to-use method to recognize motions of limbs and trunk. In this paper, we developed a wearable velocity tracking device using two orthogonally-placed micro flow sensors to implement three-dimensional motion velocity measurement. In addition, we proposed a functional link artificial neural network (FLANN) model to extract trunk velocity and relative limb velocity from an absolute limb motion detected by the wearable tracking device according to their different dynamic features. Experiments were conducted to validate the effectiveness of the velocity tracking methodology. Results showed the proposed method with wearable device enables real-time measurements of motion velocities of limb and trunk, which were free of accumulated error, robust for dynamic walking and running, and simple to use.

Comparison of age-specific leg extensor muscle function torque-time and rapid velocity attributes across the adult lifespan: A relative deficiency investigation.

The purposes of this study were to examine the age-related differences in absolute and normalized torque-time parameters in five distinct groups across the adult lifespan, and the relationship between rapid strength and limb acceleration capacities across the lifespan. One-hundred and thirty-six healthy men were categorized as young athletes (n=27; age=20.7yrs), young controls (n=32; 21.9yrs), middle young (n=32; 49.8yrs), middle old (n=15; 58.9yrs), and old (n=30; 71.3yrs) cohorts. Participants performed maximal voluntary contractions (MVCs) of the leg extensors under isometric and isokinetic (240deg.·s-1) conditions. Outcome measures included peak torque (PT), absolute and MVC normalized (norm) rate of torque development (RTD) at 50 and 200ms, RTD50/PT ratio, and rate of velocity development (RVD). The PT and absolute RTD at 200ms declined from young to old age (P<.05). The middle age groups exhibited an overall preservation of early RTD, and a potential enhancement of early normalized RTD (P=.06 for middle young vs. controls, for RTDnorm50). The RTD50/PT ratio was higher in the middle young (P<.05) compared to both the young groups. Generally, the RVD declined more linearly and exhibited worse preservation at mid-life than the early absolute or normalized RTD variables. All absolute torque-time variables were correlated (r=0.43-0.73, P<.001) to the RVD for all groups combined. These findings showed distinct age-related declines occurred for different muscle function parameters unique to specific stages of the lifespan. Normalized RTD variables may reveal plausible mechanisms of age-related neuromuscular changes and the RTD50/PT ratio may be a useful tool for determining relative deficiencies, such that mid-life adults (45-64yrs) should address their relative limitation of PT by enhancing strength at mid-life, whereas older adults (65+ yrs) may need more emphasis on RTD improvements. In addition, both mid-life and older men should seek to improve rapid limb velocity capacities due to the susceptibility of RVD to decline more incrementally across the lifespan. Such information may help to improve anti-aging strategies by countering age-specific muscle function deficiencies and may improve mid-life adults' ability to transition better functionally into old age.

Early Impulse Control: Treatment of Potential Errors within Pre-Programming and Control

Early aiming adjustments following an online perturbation are made possible by impulse control. This process may unfold even earlier when perturbations impose a greater risk of a costly overshoot error. Participants executed upward and downward aims to mediate the cost of potential errors—downward overshoots require more energy to correct against gravity. On 33% of the trials, texture elements on the aiming surface were shifted following onset to appear congruent or incongruent with the aiming direction, and consequently generate a misperception of the limb moving slower or faster, respectively. Thus, the risk of potential errors could be influenced by the online perturbation (e.g., increased perceived likelihood of overshooting following the incongruent background). Findings indicated greater undershooting for down compared to up, which reflects the principle of movement optimisation. There was also more undershooting for an incongruent compared to congruent background, which is consistent with early online adjustments counter-acting the misperceived limb velocity. However, there were no interactions throughout the movement trajectory. We suggest that while the initial pre-programme considers the cost of potential errors (target direction), early impulse control fails to discriminate the likelihood of these errors occurring following an online perturbation (moving background).

The role of the upper and lower limbs in front crawl swimming: The thoughts and practices of expert high-performance swimming coaches

The perceptions of high-performance swimming coaches regarding the relative contribution of the upper and lower limbs are crucial in optimising athletic performance through subsequent prescription of training. Problematically, examination of these perspectives is lacking. To develop knowledge in this area, perceptions regarding the upper and lower limb velocity and metabolic contributions and reasoning surrounding whole body, arms-only and legs-only training prescription (referred to as swim, pull and kick, respectively) were garnered from seven male expert swimming coaches. The semi-structured interviews were transcribed verbatim by the lead researcher. Thematically analysed through open and axial-coding, results revealed that all coaches believed the upper limbs were the primary velocity generators but placed great importance on having well-conditioned muscles of the lower limbs. All coaches identified multiple interrelated parameters contributing to velocity generation and metabolic cost. In a typical training week, coaches allocate, on average, 58% (40–85%), 19% (0–30%) and 22% (10–40%) of the total training volume to swim, pull and kick training, respectively. All training prescription was based on anecdotal evidence and personal experience. Considering the variability in training allocation reported by these high-performance coaches, sport scientists and developmental coaches are encouraged to understand how factors such as the distance specialisation of the swimmers, injury status, stroke technique and physiological conditioning status of the upper and lower limb muscles influence the prescription of swim, pull and kick training within a typical training season.

Evaluation of Fidgety Movements of Infants Based on Gestalt Perception Reflects Differences in Limb Movement Trajectory Curvature

Infants aged 2 to 5 months show spontaneous general movements (GMs) of the whole body, which are referred to as fidgety movements (FMs). Although previous studies have shown that evaluation of GMs by the General Movement Assessment (GMA) has predictive value about later neurological impairments, it remains unknown whether raters consistently perceive and rate such complex kinematic information. The purpose of this study was to construct a method to reveal which movement features are associated with each rater's evaluation of FMs based on the GMA. GMA scores of 163 healthy infants aged 11 to 16 weeks postterm were matched with data obtained from a 3-dimensional motion analysis system. Three physical therapists performed the GMA and classified GMs into 9 types, from which we focused on 3 subtypes differing in the temporal organization of FMs (continual, intermittent, and sporadic FMs). We also calculated 6 movement indices (average velocity of limb movements, number of movement units, kurtosis of acceleration, jerk index, average curvature, and correlation between limb velocities) for arms and legs for each infant and analyzed which movement indices were associated with the ratings of the 3 FM subtypes by each rater. Only the average curvature differed significantly among the ratings of the 3 FM subtypes for all 3 raters. Each rater showed significant differences in the average curvature in either arms or legs. It is difficult to generalize the present results to raters with various levels of expertise and experience in using the GMA. This issue calls for further research. The method used revealed commonality and individuality about the perceived movement features that can be associated with the rating of FMs.

Monitoring of human neuromusculoskeletal system performance through model-based fusion of electromyogram signals and kinematic/dynamic variables

This article demonstrates feasibility of utilizing model-based approach for monitoring the performance of human neuromusculoskeletal systems. The performance monitoring method utilizes an autoregressive moving-average model with exogenous inputs to link signatures extracted from electromyogram signals, to the forces produced by the limbs and limb velocities. This model is then utilized to quantify and track changes in the neuromusculoskeletal system dynamics over time. The changes were modeled using a measure of overlap between the distribution of 1-step-ahead model prediction errors observed at the beginning of the exercise, when the subject was rested, and 1-step-ahead prediction errors observed at any other time during exercise. As the subjects proceeded with their exercises and got increasingly tired, the distribution of modeling errors changed and diverged from the initially observed one, causing the overlap between the original and the most recent distributions of modeling errors, referred to as the Freshness Similarity Index, to decrease. Thus, Freshness Similarity Index could be used as a quantitative measure of the level of degradation the neuromusculoskeletal system performance through the exercise. The methodology was evaluated in two experiments, one related to an activity involving lower limb contractions, and the other involving jaw joint movements. In both cases, a decreasing trend in the Freshness Similarity Index clearly illustrated changes in neuromusculoskeletal system performance as exercise progressed. Furthermore, after rest, Freshness Similarity Index observed in both exercises recovered to their original levels, quantitatively and meaningfully showing that the corresponding neuromusculoskeletal systems of the two subjects indeed rested.

Dominant/non-dominant support limb kinematics and approach run parameters in futsal kicking of stationary and rolling ball.

Task constraints and players' asymmetry influences on lower extremity (i.e. kicking limb) kinematics during futsal instep kicking. However, support limb behavior when shooting in a futsal context was not previously investigated, and its potential role on such discrepant motor outputs is still unclear. Thus, the study aimed to compare kinematic features of the support limb and approach run between kicking a stationary and a rolling ball using dominant and non-dominant limbs. Ten futsal players participated (21.88±2.86 years-old, 73.66±4.17 kg and 1.75±0.04 m) and performed kicks (five per limb per condition) with the dominant and non-dominant limbs in stationary and rolling ball conditions. Kinematic analysis comprised determination of support limb angular joint (hip, knee and ankle) displacement and velocity, approach run distance, angle, linear velocity, step length and width, support foot-to-ball distance, ball velocity (120 Hz) and accuracy (60 Hz). Hip adjustments (greater extension) in the support limb when kicking a rolling ball contributed in maintaining similar performance (e.g., ball velocity) to kicking a stationary ball, compensating for the lower approach run velocity and longer support foot to ball distance. Kicking with the non-dominant limb demonstrated a lower approach run velocity and the non-dominant support limb presented different angular motion compared to the dominant support limb in hip (< internal rotation), knee (< flexion), and ankle joints (< plantar flexion), being harmful to performance in both kicking stationary and rolling balls. Kicking a stationary and rolling ball presented similar performance, but compared to the dominant side, futsal instep kicks performed with the non-dominant support limb induces lower approach run velocity and inefficient angular joint motion, either harmful to performance output.

Analysis of Movement Quality in Full-Body Physical Activities

Full-body human movement is characterized by fine-grain expressive qualities that humans are easily capable of exhibiting and recognizing in others’ movement. In sports (e.g., martial arts) and performing arts (e.g., dance), the same sequence of movements can be performed in a wide range of ways characterized by different qualities, often in terms of subtle (spatial and temporal) perturbations of the movement. Even a non-expert observer can distinguish between a top-level and average performance by a dancer or martial artist. The difference is not in the performed movements--the same in both cases--but in the “quality” of their performance. In this article, we present a computational framework aimed at an automated approximate measure of movement quality in full-body physical activities. Starting from motion capture data, the framework computes low-level (e.g., a limb velocity) and high-level (e.g., synchronization between different limbs) movement features. Then, this vector of features is integrated to compute a value aimed at providing a quantitative assessment of movement quality approximating the evaluation that an external expert observer would give of the same sequence of movements. Next, a system representing a concrete implementation of the framework is proposed. Karate is adopted as a testbed. We selected two different katas (i.e., detailed choreographies of movements in karate) characterized by different overall attitudes and expressions (aggressiveness, meditation), and we asked seven athletes, having various levels of experience and age, to perform them. Motion capture data were collected from the performances and were analyzed with the system. The results of the automated analysis were compared with the scores given by 14 karate experts who rated the same performances. Results show that the movement-quality scores computed by the system and the ratings given by the human observers are highly correlated (Pearson’s correlations r = 0.84, p = 0.001 and r = 0.75, p = 0.005).

Arthro-Biomechanical Investigation of the Tarsal Joint of One-Humped Camel (Camelus dromedarius) during gait: Forensic Biomechanics Evidence

It is expected that dromedary camel’s tarsus plays a crucial role in survivals in the arid and semiarid regions. These regions are open and the dromedary camel is tall with long legs. Thus, databases of biomechanical variables are needed to investigate the changes of velocity, displacement, angular changes as well as anatomical consideration of tarsal joint during walking and stance phase. Nine healthy camels of three different sizes and ages were selected for gait analysis using motion track program. Moreover, five tarsal joints cadavers obtained for 3D reconstruction computed tomography. The present study stated that, tarsal joint is a hinge biaxial joint, primarily allowing flexion, extension and small amount of rotation and gliding movement. The gait analysis during walking revealed some data of hind limb velocity, angular change and displacement of tarsal joint. Different sizes of camel had no significant effect on average and minimum value of velocity of hind limb during walking. Medium sized camel showed higher degree of extension of tarsal joint than small and large one. Medium and large camel showed significant higher vertical (p=0.01) and horizontal (p=0.05) displacement of right tarsal joint than small camel during walking. We anticipate our findings can be a useful tool in lameness investigation to discriminate between the normal and diseased gait as expecting the nature of the inhabitant environment as well as add promising evidence in the field of forensic biomechanics to avoid legal violations in racing camels.