Limb Joint Torque Research Articles

A Fast Calibration Method for an sEMG-Based Lower Limb Joint Torque Estimation Model

The joint torque estimation model based on surface electromyography (sEMG) signals needs to recalibrate the model parameters when used for joint torque estimation at different volunteers. However, the feature transferability drops significantly in higher task-specific layers, which reduce the performance of the model. The generalization of joint torque estimation models among different volunteers has become a challenge. In this paper, a fast calibration method based on a deep adaptive regression network is proposed to reduce the frequency and time of model recalibration when volunteers change. The proposed method associates source domain (SD) data with target domain (TD) data through migration learning. The maximum mean difference (MMD) adaptive method is used to migrate the model trained in the SD dataset to the TD dataset, which avoids the recalibration required in the joint torque estimation model. The experimental results show that the proposed method can improve the migration ability of the model used for estimating joint torque and achieve the generalization application of the model on different volunteer datasets. Moreover, the proposed method can reduce the calibration operations and iterations of the model caused by volunteer changes and improve the speed of joint torque estimation. The optimal normalized root mean square error (NRMSE) and Pearson correlation coefficient (ρ) of knee extension/flexion joint torque estimation reached 0.02198/0.02565 and 0.9892/0.9839, respectively.

Lower Limb Joint Torque Prediction Using Long Short-Term Memory Network and Gaussian Process Regression

The accurate prediction of joint torque is required in various applications. Some traditional methods, such as the inverse dynamics model and the electromyography (EMG)-driven neuromusculoskeletal (NMS) model, depend on ground reaction force (GRF) measurements and involve complex optimization solution processes, respectively. Recently, machine learning methods have been popularly used to predict joint torque with surface electromyography (sEMG) signals and kinematic information as inputs. This study aims to predict lower limb joint torque in the sagittal plane during walking, using a long short-term memory (LSTM) model and Gaussian process regression (GPR) model, respectively, with seven characteristics extracted from the sEMG signals of five muscles and three joint angles as inputs. The majority of the normalized root mean squared error (NRMSE) values in both models are below 15%, most Pearson correlation coefficient (R) values exceed 0.85, and most decisive factor (R2) values surpass 0.75. These results indicate that the joint prediction of torque is feasible using machine learning methods with sEMG signals and joint angles as inputs.

Study on Two Typical Progressive Motions in Tai Chi (Bafa Wubu) Promoting Lower Extremity Exercise.

By comparatively investigating the joints, muscles and bones of the lower extremity during two progressive motions in Bafa Wubu and normal walking, this paper aims to enrich the diversity of walking exercise and scientifically provide theoretical guidance for primary practitioners. The scientific training methods and technical characteristics of Bafa Wubu, as well as its contribution to comprehensive exercise of the lower extremities, are further explored. A total of eight professional athletes of Tai Chi at the national level were recruited. The kinetic parameters of the lower extremity were calculated using AnyBody 7.2 musculoskeletal modeling. Stress analysis of the iliac bone was performed using an ANSYS 19.2 workbench. In Bafa Wubu, the ground reaction force during two progressive motions was significantly smaller than that noted during normal walking. During warding off with steps forward and laying with steps forward, the load at the three joints of the lower extremity was significantly smaller than that during normal walking in the frontal plane, but significantly greater than that noted during normal walking in the vertical axis. In addition, the lower limb joint torque was higher than that of normal walking in both progressive movements, and lower limb muscle activation was higher. The iliac bone loads during the two progressive motions were larger than those during normal walking, and the maximum loading point differed. This is the first study to demonstrate the biomechanical performance of Bafa Wubu in professional athletes of Tai Chi. Two progressive motions of Bafa Wubu require the lower extremity to be slowly controlled, thereby resulting in a smaller ground reaction force. In addition, the loads of the three joints at the lower extremity all increase in the vertical direction and decrease in the lateral direction, reducing the possibility of lateral injury to the joints. In addition, the two progressive motions significantly enhance the muscle strength of the plantar flexion muscles, dorsiflexor, and muscles around the thigh, and effectively stimulate the bones of the lower extremity. Therefore, progressive motion training contributes to improving the controlling and supporting capabilities of the lower extremities during normal walking.

Lowe limb joint torque estimation using EMG-driven neuromusculoskeletal models with cluster approach

Lowe limb joint torque estimation using EMG-driven neuromusculoskeletal models with cluster approach

MEASUREMENT, PREDICTION AND VALIDATION OF HUMAN GAIT TORQUE FOR LOWER LIMB ASSISTIVE DEVICES

The lower limb rehabilitation process requires external control inputs based on joint kinematics and kinetics to its actuator for generating the motion of a robotic assistive device. This paper describes the procedures for measuring, predicting and validating the joint kinematics and kinetics of human gait for the lower limb exoskeleton. The high-speed multi-camera-based video system associated with passive optical markers and a force plate sensor is used to measure the gait data. The lower limb joint torques have also been predicted using three different machine learning regression models, viz. Decision Tree (DT), Gaussian Process Regression (GPR) and Support Vector Machine (SVM). The analysis is further validated with the geometry-based analytical method. Three lower limb joint torques have been predicted by utilizing gait period, joint angle, joint velocity and joint acceleration as the predictors. The lowest average 10-fold cross-validation Root Mean Square Error (RMSE) using the DT model between measured and predicted torques have been recorded for the ankle, knee and hip joint as 1.9521, 1.5527 and 1.5684[Formula: see text]Nm, respectively. This study enhances the field of medical rehabilitation by providing the required knowledge of human gait kinematics/kinetics and predicting the joint torque profile without any force sensor.

Time-constrained Optimization of Sit-to-stand Movements in Contact with the Environment

This study aims to evaluate effects of different lower limb joint torque constraints on the motion trajectory of an sit-to-stand movement (STS) grasping an assistive device by simulating the STS with an assistive device using a human model with different lower limb joint torque constraints at various second lengths. This is an initial study for estimating lower limb muscle strength from the motion trajectory of the STS grasping an assistive device. In this study, instead of measuring many human subjects, optimal motion trajectories are calculated and simulated. Equations of the STS using the assistive device are first established using a rigid link model with both hands grasping the assistive device. Then, equations of motion and physical constraints such as joint range of motion and torque limitations are used as constraint conditions, and the sum of squares of joint torque, which calculates the action with the minimum muscle load on the body, is used as an evaluation function to optimize the STS. During optimization, calculations are performed with several types of joint torque conditions and end-time, i.e., the time required to complete the operation. By comparing several types of joint torque condition movements, the differences in the effects of different joint torque constraints on the motion trajectory of the STS grasping the assistive device can be determined.

Biomechanical analysis of the pitching characteristics of adult amateur baseball pitchers throwing standard and lightweight balls.

[Purpose] The purpose of this study was to determine the relationship between pitching weight and pitching mechanics, including ball reaction force (BRF) and temporal parameters, for the prevention of throwing injury in adult amateur pitchers. [Participants and Methods] Twenty adult male amateur pitchers (mean age, height, and body mass: 26 ± 3.4 years, 1.7 ± 0.03 m, and 71.6 ± 9.5 kg, respectively) randomly pitched light (110 g) and heavy (145 g) baseballs at maximum velocity. Kinematic, kinetic, and temporal parameters were compared between the light and heavy balls. [Results] Pitching heavy balls significantly increased the BRF to 9.2 N and maximum trunk rotation angular velocity to 26.2°/sec, and decreased the ball speed to 1.4 m/sec and upper limb joint torque efficiency and shoulder internal rotation angular velocity at the moment of ball release at 250.8°/sec. Furthermore, the peak temporal kinetic parameters until ball release appeared early in the throwing of the heavy ball. [Conclusion] Adult amateur pitchers who pitched heavy balls had greater BRF; had decreased upper limb joint torque efficiency, ball speed, and arm angular velocity; and reached maximum kinetics early. Adult amateur pitchers may be at risk of throwing injuries due to throwing of heavy balls.

Characteristics of lower limb force exertion during diving motions by collegiate male soccer goalkeepers

ABSTRACTIntroduction: Diving is a high-intensity movement with a determining effect on the soccer game. So, the aim of this study was to evaluate the effects of distance and height on lower limb kinetics and ground reaction force (GRF) during a diving motion of soccer goalkeepers. Methods:The analysis was based on whole-body three-dimensional motion capture (250 Hz) with GRFs recorded using force plates (1000 Hz). Lower limb joint torque and power profile were computed using standard inverse dynamics equations. Results: Significant effects of both dive distance and ball height were identified based on the magnitude and orientation of the GRF vector for the ball-side leg (BS leg) and on the magnitude of the GRF vector for the contralateral-side leg (CS leg). Overall, flexion torques were negligible, with significant contributions of the hip and ankle to extension torques and power. Of note, the BS leg provided an important negative (braking) power, which increased as a function of increasing ball distance and height. Conclusion: From these results, spatial parameters of the goalkeeper's diving motion appear to affect the kinetics of the BS leg.

A comparison of kinetics in the lower limbs between baseball tee and pitched ball batting

In this study, the kinetic characteristics of lower limbs during batting were investigated by comparing batting off a tee with batting a pitched ball. Participants were 10 male collegiate baseball players who performed tee batting (TB) and batting using a pitching machine (MB; approximate ball speed: 33.3 m/s). Three-dimensional coordinate data were acquired using a motion capture system, and ground reaction forces were measured using three force platforms. Lower limb joint torques were obtained by inverse dynamics calculations. The results indicated that the angular velocity of the lower trunk was larger in TB than in MB for rotation. The swing time from stride foot contact with the ground to ball impact was significantly longer in MB than in TB. The angular impulses of bilateral hip adduction, pivot hip external rotation, and stride hip and knee extension torques were significantly larger in MB, suggesting that batters exert these joint torques earlier for pitched balls to handle time constraints by changing the rotation of the lower trunk in response to the unknown ball location and speed in MB. These findings will help to fill a gap in the literature and provide coaching insights for improving batting motion.

Effect of wire assist suit on gait and lower limb joint torques

Effect of wire assist suit on gait and lower limb joint torques

Development of KIINCE: A kinetic feedback-based robotic environment for study of neuromuscular coordination and rehabilitation of human standing and walking.

IntroductionThe objective of this article is to introduce the robotic platform KIINCE and its emphasis on the potential of kinetic objectives for studying and training human walking and standing. The device is motivated by the need to characterize and train lower limb muscle coordination to address balance deficits in impaired walking and standing.MethodsThe device measures the forces between the user and his or her environment, particularly the force of the ground on the feet (F) that reflects lower limb joint torque coordination. In an environment that allows for exploration of the user’s capabilities, various forms of real-time feedback guide neural training to produce F appropriate for remaining upright. Control of the foot plate motion is configurable and may be user driven or prescribed. Design choices are motivated from theory of motor control and learning as well as empirical observations of F during walking and standing.ResultsPreliminary studies of impaired individuals demonstrate the feasibility and potential utility of patient interaction with kinetic immersive interface for neuromuscular coordination enhancement.ConclusionApplications include study and rehabilitation of standing and walking after injury, amputation, and neurological insult, with an initial focus on stroke discussed here.

野球打撃動作における身体関節トルクの累積的効果

Motion-dependent term (MDT), which consists of centrifugal force, Coriolis force and gyroscopic effect moment expressed in the equation of motion for a multi-link system, plays significant roles in the generation of bat head speed through not instantaneous effect but cumulative effect of the exerting joint torques in baseball batting. According to our previous studies that calculate dynamics contributions of the whole-body joint torques considering generating factor of the MDT, the forward/backward rotational torque (FBR torque) at torso joint plays a significant role in the generation of bat head speed. These studies, however, show that the lower limb joint torques do not contribute directly to the bat head speed. Therefore, the purpose of this study was to make clear the functional roles of the lower limb joint torques considering the cumulative effect of exerting joint torques. The whole-body with bat was modelled as a system of sixteen-rigid linked segments. The contributions of the lower limb joint torques to the exerting FBR torque at torso joint were quantified through dynamic contribution equation, which relates lower limb joint torques to the torso FBR torque, derived from both dynamics joint force contribution equation of whole-body system and equilibrium balance equation with respect to rotational movement of the lower trunk segment. The results obtained in this study show 1) lower limb joint torque, especially flexion/extension torque at both hip joints, is a large contributor to the generation of the torso FBR torque, and 2) lower trunk inertial force term and other terms are small contributors to the FBR torque. The development of this analytical method would enable us to quantify the contribution of the lower limb joint torques.

A mechanical link model of two-toed sloths: no pendular mechanics during suspensory locomotion

Sloths are morphologically specialized in suspensory quadrupedal locomotion and posture. During steady-state locomotion they utilize a trot-like footfall sequence. Contrasting the growing amount of published accounts of the functional morphology and kinematics of sloth locomotion, no study concerned with the dynamics of their quadrupedal suspensory locomotion has been conducted. Brachiating primates have been shown to travel at low mechanical costs using pendular mechanics, but this is associated with considerable dynamic forces exerted onto the support. To test whether sloth locomotion can be described by simple connected pendulum mechanics, we analyzed the dynamics of sloth locomotion with use of a mechanical segment link model. The model integrates the body segment parameters and is driven by kinematic data with both segment parameters and kinematic data obtained from the same sloth individual. No simple pendular mechanics were present. We then used the model to carry out an inverse dynamic analysis. The analysis allowed us to estimate net limb joint torques and substrate reaction forces during the contact phases. Predominant flexing limb joint torque profiles in the shoulder, elbow, hip, and knee are in stark contrast to published dominant extensor torques in the limb joints of pronograde quadrupedal mammals. This dissimilarity likely reflects the inverse orientation of the sloth towards the gravity vector. Nevertheless, scapular pivot and shoulder seem to provide the strongest torque for progression as expected based on unchanged basic kinematic pattern previously described. Our model predicts that sloths actively reduce the dynamical forces and moments that are transmitted onto the support. We conclude that these findings reflect the need to reduce the risk of breaking supports because in this case sloths would likely be unable to react quickly enough to prevent potentially lethal falls. To achieve this, sloths seem to avoid the dynamical consequences of effective pendular mechanics.

Quantification of functional weakness and abnormal synergy patterns in the lower limb of individuals with chronic stroke

BackgroundThe presence of abnormal muscle activation patterns is a well documented factor limiting the motor rehabilitation of patients following stroke. These abnormal muscle activation patterns, or synergies, have previously been quantified in the upper limbs. Presented here are the lower limb joint torque patterns measured in a standing position of sixteen chronic hemiparetic stroke subjects and sixteen age matched controls used to examine differences in strength and coordination between the two groups.MethodsWith the trunk stabilized, stroke subjects stood on their unaffected leg while their affected foot was attached to a 6-degree of freedom load cell (JR3, Woodland CA) which recorded forces and torques. The subjects were asked to generate a maximum torque about a given joint (hip abduction/adduction; hip, knee, and ankle flexion/extension) and provided feedback of the torque they generated for that primary joint axis. In parallel, EMG data from eight muscle groups were recorded, and secondary torques generated about the adjacent joints were calculated. Differences in mean primary torque, secondary torque, and EMG data were compared using a single factor ANOVA.ResultsThe stroke group was significantly weaker in six of the eight directions tested. Analysis of the secondary torques showed that the control and stroke subjects used similar strategies to generate maximum torques during seven of the eight joint movements tested. The only time a different strategy was used was during maximal hip abduction exertions where stroke subjects tended to flex instead of extend their hip, which was consistent with the classically defined "flexion synergy." The EMG data of the stroke group was different than the control group in that there was a strong presence of co-contraction of antagonistic muscle groups, especially during ankle flexion and ankle and knee extension.ConclusionThe results of this study indicate that in a standing position stroke subjects are significantly weaker in their affected leg when compared to age-matched controls, yet showed little evidence of the classic lower-limb abnormal synergy patterns previously reported. The findings here suggest that the primary contributor to isometric lower limb motor deficits in chronic stroke subjects is weakness.

1P1-3F-D1 3 次元計測装置 OPTOTRAK3020 を用いた運動中における人間の上肢関節トルク計測システムの構築 : 人間とロボットの協調作業における人間の運動の定量的評価法の提案

人間とロボットによる協調作業において, 人間の腕の運動を定量的に評価するために, 人間の腕を7自由度モデルとし, 3次元計測装置を用いて各関節に生じるトルクを算出する計測システムを構築する。

Changes in upper limb joint torque patterns and EMG signals with fatigue following a stroke

Purpose : Little is known concerning changes in neuromuscular fatigue following a stroke. The purpose of this study was to evaluate the effect of a stroke on fatigue-related changes in upper limb torque patterns and electromyographic signals. Method : The paretic and non-paretic upper limb of 10 adults (51 - 79 years) who had a stroke (time since stroke: 3 - 75 months) were compared. Subjects had to perform a fatigue task consisting of a sustained maximal isometric contraction in elbow flexion until torque decreased to below 50% of initial. The main variables of interest assessed before, during and after fatigue were: (1) the torque in elbow flexion, as well as associated forces/torques at the shoulder and forearm; (2) the level of voluntary activation; (3) the amplitude (RMS); and (4) frequency content (median frequency) of electromyographic signals. Results : Compared to the non-paretic side, the paretic side showed a lower level of voluntary activation and higher relative torque levels at the forearm and shoulder which could both be exaggerated with fatigue, and a lesser fatigue-related decrease in median frequency. Conclusions : Thus, greater fatigue-related changes in features of the central command (ability to maximally activate a muscle and ability to isolate effort to a muscle group) were observed for the paretic compared with the non-paretic side. This could be a confounding factor when assessing changes in peripheral measures of fatigue following a stroke using voluntary contractions.