Resultant Joint Torque Research Articles

Research on the biomimetic quadruped jumping robot based on an efficient energy storage structure

AbstractThe ability of quadruped robots to overcome obstacles is a critical factor that limits their practical application. Here, a design concept and a control algorithm are presented that aim at enhancing the explosive force of quadruped robots during jumping by utilizing elastic energy storage components. The hind legs of the quadruped robot are designed as energy storage units. Tension springs are utilized as components for storing energy and are installed in a parallel structure on the hind leg. Energy is stored during the compression process of the robot’s torso and released during the jumping phase. The optimal foot force is calculated using a single rigid body model. The mapping relationship between the force applied to the foot and the resulting joint torque is established by developing a dynamic model of the hind legs. Simulation experiments were conducted using the Webots physics engine to compare the impact of varying spring stiffness on joint torque during the jumping process. This study determined the optimal spring stiffness under specific conditions. The hind legs’ torque saving ratio reaches 19%, and the energy-saving ratio reaches 13%, which validates the effectiveness and feasibility of integrating elastic energy storage components.

A wearable gait lab powered by sensor-driven digital twins for quantitative biomechanical analysis post-stroke.

Commonly, quantitative gait analysis post-stroke is performed in fully equipped laboratories housing costly technologies for quantitative evaluation of a patient's movement capacity. Combining such technologies with an electromyography (EMG)-driven musculoskeletal model can estimate muscle force properties non-invasively, offering clinicians insights into motor impairment mechanisms. However, lab-constrained areas and time-demanding sensor setup and data processing limit the practicality of these technologies in routine clinical care. We presented wearable technology featuring a multi-channel EMG-sensorized garment and an automated muscle localization technique. This allows unsupervised computation of muscle-specific activations, combined with five inertial measurement units (IMUs) for assessing joint kinematics and kinetics during various walking speeds. Finally, the wearable system was combined with a person-specific EMG-driven musculoskeletal model (referred to as human digital twins), enabling the quantitative assessment of movement capacity at a muscle-tendon level. This human digital twin facilitates the estimation of ankle dorsi-plantar flexion torque resulting from individual muscle-tendon forces. Results demonstrate the wearable technology's capability to extract joint kinematics and kinetics. When combined with EMG signals to drive a musculoskeletal model, it yields reasonable estimates of ankle dorsi-plantar flexion torques (R 2=0.65±0.21) across different walking speeds for post-stroke individuals. Notably, EMG signals revealing an individual's control strategy compensate for inaccuracies in IMU-derived kinetics and kinematics when input into a musculoskeletal model. Our proposed wearable technology holds promise for estimating muscle kinetics and resulting joint torque in time-limited and space-constrained environments. It represents a crucial step toward translating human movement biomechanics outside of controlled lab environments for effective motor impairment monitoring.

How the acceleration phase influences energy flow and the resulting joint moments of the throwing shoulder in the deceleration phase of the javelin throw.

The throwing motion in the javelin throw applies high loads to the musculoskeletal system of the shoulder, both in the acceleration and deceleration phases. While the loads occurring during the acceleration phase and their relationship to kinematics and energy flow have been relatively well investigated, there is a lack of studies focusing the deceleration phase. Therefore, the aim of this study is to investigate how the throwing arm is brought to rest, which resultant joint torques are placed on the shoulder and how they are influenced by the kinematics of the acceleration phase. The throwing movement of 10 javelin throwers were recorded using a 12-infrared camera system recording at 300 Hz and 16 markers placed on the body. Joint kinematics, kinetics and energy flow were calculated between the touchdown of the rear leg and the timepoint of maximum internal rotation after release +0.1 s. Elastic net regularization regression was used to predict the joint loads in the deceleration phase using the kinematics and energy flow of the acceleration phase. The results show that a significant amount of energy is transferred back to the proximal segments, while a smaller amount of energy is absorbed. Furthermore, relationships between the kinematics and the energy flow in the acceleration phase and the loads placed on the shoulder joint in the deceleration phase, based on the elastic net regularized regression, could be established. The results indicate that the loads of the deceleration phase placed on the shoulder can be influenced by the kinematics of the acceleration phase. For example, an additional upper body forward tilt can help to increase the braking distance of the arm and thus contribute to a reduced joint load. Furthermore, the energy flow of the acceleration phase can be linked to joint stress. However, as previously demonstrated the generation of mechanical energy at the shoulder seems to have a negative effect on shoulder loading while the transfer can help optimize the stress. The results therefore show initial potential for optimizing movement, to reduce strain and improve injury prevention in the deceleration phase.

Automated spatial localization of ankle muscle sites and model-based estimation of joint torque post-stroke via a wearable sensorised leg garment.

Assessing a patient's musculoskeletal function during over-ground walking is a primary objective in post-stroke rehabilitation, due to the importance of walking recovery for everyday life. However, the quantitative assessment of musculoskeletal function currently requires lab-constrained equipment, and labor-intensive analyses, which hampers assessment in standard clinical settings. The development of fully wearable systems for the online estimation of muscle-tendon forces and resulting joint torque would aid clinical assessment of motor recovery, it would enhance the detection of neuro-muscular anomalies and it would consequently enable highly personalized treatments. Here, we present a wearable technology that combines (1) a soft garment for the human leg sensorized with 64 flexible and dry electromyography (EMG) electrodes, (2) a generalized and automated algorithm for the localization of leg muscle sites, and (3) an EMG-driven musculoskeletal modeling framework for the estimation of ankle dorsi-plantar flexion torques. Our results showed that the automated clustering algorithm could detect muscle locations in both healthy and post-stroke individuals. The estimated muscle-specific EMG envelopes could be used to drive forward person-specific musculoskeletal models and estimate resulting joint torques accurately across all healthy and post-stroke individuals and across different walking speeds (R2 >0.82 and RMSD <0.16). The technology we proposed opens new avenues for automated muscle localization and quantitative musculoskeletal function assessment during gait in both healthy and neurologically impaired individuals.

Early Postoperative Activities of Daily Living Do Not Adversely Affect Joint Torques or Translation Regardless of Capsular Condition: A Cadaveric Study

To evaluate the impact of capsular management on joint constraint and femoral head translations during simulated activities of daily living (ADL). Using 6 (n= 6) cadaveric hip specimens, the effect of capsulotomies and repair was then evaluated during simulated ADL. Joint forces and rotational kinematics associated with gait and sitting, adopted from telemeterized implant studies, were applied to the hip using a 6-degrees of freedom (DOF) joint motion simulator. Testing occurred after creation of portals, interportal capsulotomy (IPC), IPC repair, T-capsulotomy (T-Cap), partial T-Cap repair, and full T-Cap repair. The anterior-posterior (AP), medial-lateral (ML), and axial compression DOFs were operated in force control, whereas flexion-extension, adduction-abduction, and internal-external rotation were manipulated in displacement control. Resulting femoral head translations and joint reaction torques were recorded and evaluated. Subsequently, the mean-centered range of femoral head displacements and peak signed joint restraint torques were calculated and compared. During simulated gait and sitting, the mean range of AP femoral head displacements with respect to intact exceeded 1% of the femoral head diameter after creating portals, T-Caps, and partial T-Cap repair (Wilcoxon signed rank P < .05); the mean ranges of ML displacements did not. Deviations in femoral head kinematics varied by capsule stage but were never very large. No consistent trends with respect to alterations in peak joint restrain torques were observed. In this cadaveric biomechanical study, capsulotomy and repair minimally affected resultant femoral head translation and joint torques during simulated ADLs. The tested ADLs appear safe to perform after surgery, regardless of capsular status, because adverse kinematics were not observed. However, further study is required to determine the importance of capsular repair beyond time-zero biomechanics and the resultant effect on patient-reported outcomes.

Kinetics of four limb joints during kick-start motion in competitive swimming

ABSTRACT The kick-start technique in competitive swimming generates a force acting on the starting platform owing to gravity, muscle contraction and resulting joint torque. To understand optimal body movement on the starting platform for maximising take-off velocity, it is necessary to investigate the joint torque in relation to the joint’s rotation effects. Joint torques were calculated by inverse dynamics using kinetic and kinematic data. A one-way ANOVA showed significantly greater extensional torque for shoulders than for elbows or wrists, and for hips than for knees or ankles. The results indicated that the force of the hands was mainly influenced by extension torque at the shoulder joint. Hip joint extension torque on the front side lower limb (FSLL) was mainly used for supporting the body weight until hands off. After hands off, the front-foot force originated mainly by increases in ankle joint plantar flexion and knee joint extension torque on the FSLL. Rear side lower limb torque increases in the hip, knee and ankle joints provided the rear-foot force. This investigation clarified the magnitudes and functions of each joint torque acting on the extremities during the kick-start, providing practical information for improving starting performance.

SOCCER CLEATS WITH BLADE-SHAPED STUDS AND MECHANICAL OVERLOAD IN SOCCER: A SYSTEMATIC REVIEW

ABSTRACT Soccer cleats with blade-shaped studs promote greater traction on the pitch and can be beneficial for soccer performance. On the other hand, movements with rapid changes of direction, associated with the high traction of soccer cleats, can increase overload and risk of injuries. Given the lack of consensus on the effects of these cleats on mechanical overload during specific soccer movements, the aim of this systematic review was to determine the effects of wearing cleats with bladed studs on mechanical overload in soccer. A search was conducted in the PubMed, Scopus, and Web of Science electronic databases between October and November 2017. Non-original articles were excluded, as were those not related to soccer or cleats, and those not written in English. Eight articles were included that tested the effects of bladed studs on overload and that used biomechanical tests. The tasks evaluated were: running in a straight line or with changes of direction, and landing of jumps. The resulting joint torque, soil reaction force, electromyography, and plantar pressure were measured. There was no influence of bladed shaped studs on joint torque or on ground reaction force. There was an increase in plantar pressure on the lateral part of the foot in bladed studs compared to Society cleats and running shoes. When compared with round studs, the results were inconclusive for plantar pressure. Round studs, caused greater electromyographic activity in the quadriceps muscles than bladed studs. It was concluded that wearing bladed-stud cleats does not result in greater mechanical overload during running or landing of jumps. Evidence Level I, Systematic Review.

A Control Method for Joint Torque Minimization of Redundant Manipulators Handling Large External Forces

In this paper, a control method is developed for minimizing joint torque on a redundant manipulator where an external force acts on the end-effector. Using null space control, the redundant task is designed to minimize the torque required to oppose the external force, and reduce the dynamic torque. Furthermore, the joint motion can be weighted to factor in physical constraints such as joint limits, collision avoidance, etc. Conventional methods for joint torque minimization only consider the internal dynamics of the manipulator. If external forces acting on the end-effector are inadvertently implemented in to these control methods this could lead to joint configurations that amplify the resulting joint torque. The proposed control method is verified through two different case studies. The first case study involves simulation of high-pressure blasting. The second is a simulation of a manipulator lifting and moving a heavy object. The results show that the proposed control method reduces overall joint torque compared to conventional methods. Furthermore, the joint torque is minimized such that there is potential for a manipulator to execute certain tasks beyond its nominal payload capacity.

Disturbance compensation of a dual-arm underwater robot via redundant parallel mechanism theory

Disturbance compensation is one of the major issues for underwater robots to hover as a mobile platform and to manipulate an object in an underwater environment. This paper presents a new strategy of disturbance compensation for a mobile dual-arm underwater robot using internal torques derived from redundant parallel mechanism theory. A model of the robot was analyzed by redundant serial and parallel mechanisms at the same time. The joint torque to operate the robot is obtained from a redundant serial mechanism model with null-space projection due to redundancy. The joint torque derived from the redundant parallel kinematic model is calculated to perfectly compensate for disturbances to the mobile platform and is included in the solution of the joint torque based on the serial redundant model. The resultant joint torque can generate force on the end-effector for required tasks and forces for disturbance compensation simultaneously . A simulation shows the performance of this disturbance compensation strategy. The joint torque based on the algorithm generates the desired task force and the disturbance compensation force together, and a little additional joint torque can generate a large internal force effectively due to the characteristics of a redundant parallel mechanism. The proposed method is more effective than compensation methods using thrusting force on the mobile platform.

Real-time estimation of FES-induced joint torque with evoked EMG : Application to spinal cord injured patients.

BackgroundFunctional electrical stimulation (FES) is a neuroprosthetic technique for restoring lost motor function of spinal cord injured (SCI) patients and motor-impaired subjects by delivering short electrical pulses to their paralyzed muscles or motor nerves. FES induces action potentials respectively on muscles or nerves so that muscle activity can be characterized by the synchronous recruitment of motor units with its compound electromyography (EMG) signal is called M-wave. The recorded evoked EMG (eEMG) can be employed to predict the resultant joint torque, and modeling of FES-induced joint torque based on eEMG is an essential step to provide necessary prediction of the expected muscle response before achieving accurate joint torque control by FES.MethodsPrevious works on FES-induced torque tracking issues were mainly based on offline analysis. However, toward personalized clinical rehabilitation applications, real-time FES systems are essentially required considering the subject-specific muscle responses against electrical stimulation. This paper proposes a wireless portable stimulator used for estimating/predicting joint torque based on real time processing of eEMG. Kalman filter and recurrent neural network (RNN) are embedded into the real-time FES system for identification and estimation.ResultsPrediction results on 3 able-bodied subjects and 3 SCI patients demonstrate promising performances. As estimators, both Kalman filter and RNN approaches show clinically feasible results on estimation/prediction of joint torque with eEMG signals only, moreover RNN requires less computational requirement.ConclusionThe proposed real-time FES system establishes a platform for estimating and assessing the mechanical output, the electromyographic recordings and associated models. It will contribute to open a new modality for personalized portable neuroprosthetic control toward consolidated personal healthcare for motor-impaired patients.

A weighted cost function to deal with the muscle force sharing problem in injured subjects: A single case study

The human body is an over-actuated multi-body system, as each joint degree of freedom can be controlled by more than one muscle. Solving the force-sharing problem (i.e. finding out how the resultant joint torque is shared among the muscles actuating that joint) calls for an optimization process where a cost function, representing the strategy followed by the central nervous system to activate muscles, is minimized. The main contribution of the present study has been the particular formulation of that cost function for the case of the pathological gait of a single subject suffering from anterior cruciate ligament rupture. Our hypothesis was that the central nervous system does not weight equally the muscles when trying to compensate for a lower limb injury during gait (in contrast to what is the usual practice for healthy gait where all muscles are weighted equally). This hypothesis is supported by the fact that muscle activity in injured individuals differs from that of healthy subjects. Different functions were tested until we finally came out with a cost function that was consistent with experimental electromyography measurements and inverse dynamics results for a subject suffering this particular pathology.

Optimized Configurations of Kinematically Redundant Planar Parallel Manipulator following a Desired Trajectory

Abstract This paper presents an optimization methodology for achieving minimum actuation torques of a kinematically redundant planar parallel mechanism following a desired trajectory using binary coded Genetic Algorithms (GA). A user interactive computer program developed in present work helps for obtaining inverse kinematic solution and Jacobian matrices at a given Cartesian coordinate location of the end-effector. Furthermore, the joint torques are obtained from the end-effector forces (wrench) using Jacobian matrix at every location. The resultant joint torque vector can be used to describe the objective function. The variables of the optimization problem are redundant base prismatic joint displacements and the constraints include the variable bounds and the pre-defined trajectory lying within the original workspace. The outputs of the kinematically-redundant 3-PRRR manipulator are compared against the results for a non-redundant 3-RRR manipulator. The results show that the redundant manipulator gives relatively lower input torques. Also, it is observed that while passing through singular configurations on the trajectory, finite values of torques are achieved. Results are shown for a straight-line trajectory.

Development of a Mechatronic Platform and Validation of Methods for Estimating Ankle Stiffness During the Stance Phase of Walking

The mechanical properties of human joints (i.e., impedance) are constantly modulated to precisely govern human interaction with the environment. The estimation of these properties requires the displacement of the joint from its intended motion and a subsequent analysis to determine the relationship between the imposed perturbation and the resultant joint torque. There has been much investigation into the estimation of upper-extremity joint impedance during dynamic activities, yet the estimation of ankle impedance during walking has remained a challenge. This estimation is important for understanding how the mechanical properties of the human ankle are modulated during locomotion, and how those properties can be replicated in artificial prostheses designed to restore natural movement control. Here, we introduce a mechatronic platform designed to address the challenge of estimating the stiffness component of ankle impedance during walking, where stiffness denotes the static component of impedance. The system consists of a single degree of freedom mechatronic platform that is capable of perturbing the ankle during the stance phase of walking and measuring the response torque. Additionally, we estimate the platform's intrinsic inertial impedance using parallel linear filters and present a set of methods for estimating the impedance of the ankle from walking data. The methods were validated by comparing the experimentally determined estimates for the stiffness of a prosthetic foot to those measured from an independent testing machine. The parallel filters accurately estimated the mechatronic platform's inertial impedance, accounting for 96% of the variance, when averaged across channels and trials. Furthermore, our measurement system was found to yield reliable estimates of stiffness, which had an average error of only 5.4% (standard deviation: 0.7%) when measured at three time points within the stance phase of locomotion, and compared to the independently determined stiffness values of the prosthetic foot. The mechatronic system and methods proposed in this study are capable of accurately estimating ankle stiffness during the foot-flat region of stance phase. Future work will focus on the implementation of this validated system in estimating human ankle impedance during the stance phase of walking.

Dependency of knee extension torque on different types of stabilisation

Can isolated single-joint torque measurements be used for every practical use case concerning strength prediction or does the possibility of support and stabilisation influence the results? Some studies show that, for example, using or not using handgrips influences maximum knee extension joint torques. This suggests that a muscle can transmit a higher force than it can generate. This would have incisive consequences on digital human modelling. In this case, a strength prediction model would need the information about possible contact points that could increase the resulting joint torque by recruiting further muscle groups. In this study, three stabilisation methods (waist belt, upper body restraint, handgrips and waist belt) were used for maximum isometric knee joint torque measurements using 21 young, male subjects. The results show that in contrast to some earlier studies no significant differences could be obtained. Based on the results recommendations for appropriate stabilisation are given.

Influence of selected modeling and computational issues on muscle force estimates

Knowledge of muscle forces and joint reaction forces during human movement can provide insight into the underlying control and tissue loading. Since direct measurement of the internal loads is generally not feasible, non-invasive methods based on musculoskeletal modeling and computer simulations have been extensively developed. By applying observed motion data to the musculoskeletal models, inverse dynamic analysis allow to determine the resultant joint torques, transformed then into estimates of individual muscle forces by means of different optimization procedures. Assessment of the joint reaction forces and other internal loads is further possible. Comparison of the muscle force estimates obtained for different modeling assumptions and parameters in the model can be valuable for the improvement of validity of the model-based estimations. The present study is another contribution to this field. Using a sagittal plane model of an upper limb with a weight carried in hand, and applying the data of recorded flexion and extension movement of the upper limb, the resultant muscular forces are predicted using different modeling assumptions and simulation tools. This study relates to different coordinates (joint and natural coordinates) used to built the mathematical model, muscle path modeling, muscle decomposition (change in number of the modeled muscles), and different optimization methods used to share the joint torques into individual muscles.

A sensorless torque control for Antagonistic Driven Compliant Joints

Antagonistic Driven Compliant Joints (ADCJs) are object of great interest in current robotics research, representing one of the most widely applied solutions to develop human-like and safe joints for human-robot interaction. Providing the joint with “actively” adjustable hardware compliance, ADCJs have two distinctive features: (1) the joint is powered by two independent “actuation units” and (2) each actuation unit works as a non-linear elastic element with an adjustable resting position. This paper proposes a sensorless torque control strategy suitable for ADCJs actuated robots. This method is based on two steps: (1) off-line characterization of the elasticity of the actuation units, defined by the force–elongation curve and (2) online estimation of the force exerted by each actuation unit, through a direct measure of the joint angle, and of the “resting position” of each actuation unit. The proposed force estimation method can be used to develop two independent force controllers, which can be then combined to regulate the resulting joint torque, with no need of additional torque sensors. The performance of the proposed torque control was evaluated over the shoulder and the elbow ADCJs of the 2-link 2-DOFs planar robotic arm NEURARM. The method proved to work effectively, achieving good performances on the test platform, and represents a suitable alternative to state-of-the-art sensor-based torque controls.

The Effect of Running Shoes on Lower Extremity Joint Torques

To determine the effect of modern-day running shoes on lower extremity joint torques during running. Two-condition experimental comparison. A 3-dimensional motion analysis laboratory. A total of 68 healthy young adult runners (37 women) who typically run in running shoes. All subjects ran barefoot and in the same type of stability running footwear at a controlled running speed. Three-dimensional motion capture data were collected in synchrony with ground reaction force data from an instrumented treadmill for each of the 2 conditions. Peak 3-dimensional external joint torques at the hip, knee, and ankle as calculated through a full inverse dynamic model. Increased joint torques at the hip, knee, and ankle were observed with running shoes compared with running barefoot. Disproportionately large increases were observed in the hip internal rotation torque and in the knee flexion and knee varus torques. An average 54% increase in the hip internal rotation torque, a 36% increase in knee flexion torque, and a 38% increase in knee varus torque were measured when running in running shoes compared with barefoot. The findings at the knee suggest relatively greater pressures at anatomical sites that are typically more prone to knee osteoarthritis, the medial and patellofemoral compartments. It is important to note the limitations of these findings and of current 3-dimensional gait analysis in general, that only resultant joint torques were assessed. It is unknown to what extent actual joint contact forces could be affected by compliance that a shoe might provide, a potentially valuable design characteristic that may offset the observed increases in joint torques.

Model-based estimation of muscle forces exerted during movements

Estimation of individual muscle forces during human movement can provide insight into neural control and tissue loading and can thus contribute to improved diagnosis and management of both neurological and orthopaedic conditions. Direct measurement of muscle forces is generally not feasible in a clinical setting, and non-invasive methods based on musculoskeletal modeling should therefore be considered. The current state of the art in clinical movement analysis is that resultant joint torques can be reliably estimated from motion data and external forces (inverse dynamic analysis). Static optimization methods to transform joint torques into estimates of individual muscle forces using musculoskeletal models, have been known for several decades. To date however, none of these methods have been successfully translated into clinical practice. The main obstacles are the lack of studies reporting successful validation of muscle force estimates, and the lack of user-friendly and efficient computer software. Recent advances in forward dynamics methods have opened up new opportunities. Forward dynamic optimization can be performed such that solutions are less dependent on measured kinematics and ground reaction forces, and are consistent with additional knowledge, such as the force-length-velocity-activation relationships of the muscles, and with observed electromyography signals during movement. We conclude that clinical applications of current research should be encouraged, supported by further development of computational tools and research into new algorithms for muscle force estimation and their validation.

A new non-orthogonal decomposition method to determine effective torques for three-dimensional joint rotation

This paper describes a new non-orthogonal decomposition method to determine effective torques for three-dimensional (3D) joint rotation. A rotation about a joint coordinate axis (e.g. shoulder internal/external rotation) cannot be explained only by the torque about the joint coordinate axis because the joint coordinate axes usually deviate from the principal axes of inertia of the entire kinematic chain distal to the joint. Instead of decomposing torques into three orthogonal joint coordinate axes, our new method decomposes torques into three “non-orthogonal effective axes” that are determined in such a way that a torque about each effective axis produces a joint rotation only about one of the joint coordinate axes. To demonstrate the validity of this new method, a simple internal/external rotation of the upper arm with the elbow flexed at 90° was analyzed by both orthogonal and non-orthogonal decomposition methods. The results showed that only the non-orthogonal decomposition method could explain the cause-effect mechanism whereby three angular accelerations at the shoulder joint are produced by the gravity torque, resultant joint torque, and interaction torque. The proposed method would be helpful for biomechanics and motor control researchers to investigate the manner in which the central nervous system coordinates the gravity torque, resultant joint torque, and interaction torque to control 3D joint rotations.

Biomechanics of Muscular Effort

The concept of muscular effort as it relates to the biomechanics and motor control of human movement is not clearly denned. Recently, Rosenbaum and Gregory (2002) developed a method for relating judgments of muscular effort to kinematic and kinetic variables during dynamic movements of varying speeds. However, no attempts have been made to evaluate the effects of load on muscular effort. PURPOSE: To examine the effects of load on the biomechanics of muscular effort during single-joint, upper-extremity movements. METHODS: Thirty healthy adults participated in this experiment. All participants were asked to perform cyclic elbow flexion/extension movements in the horizontal plane using their dominant arm with four different loads (0, 0.5, 1.0, and 1.5 kg) while moving at a frequency of 1.5 Hz. The participants were required to produce angular displacements that corresponded to effort levels of 1, 3, 5, 7, and 9 on a modified Borg CR-10 scale. The 20 conditions (five effort levels x four loads) were tested in random order. Angular position of the elbow joint was measured using a motion capture system; mean angular displacement (MAD), peak angular velocity (PAV), peak angular acceleration (PAA), and resultant joint torque (RJT) for each condition were calculated from the angular position-time series and anthropometric data. A two-way analysis of variance was used to assess the effects of effort and load on MAD, PAV, PAA, and RJT. RESULTS: As the effort level increased from 1–9 across the four load conditions, there were significant increases in MAD (from 9.0±2.7–75.1±2.8°;P<0.001), PAV (from 42.8±13.4–344.4±14.0°/s;P<0.001), PAA (from 430.9±147.2–3832.3±153.3°/s2;P<0.001), and RJT (from 9.3±3. 1–82.4±3.2 N-m; P<0.001). In addition, as the load increased from 0–1.5 kg across the five effort level conditions, there were significant decreases in MAD (from 46.6±2.4–35.4±2.4°;P<0.01), PAV (from 215.7±12.0–162.2±12.2°/s;P<0.01), and PAA (from 2395.0±131.7–1752.8±133.9°/s2; P<0.005); however, there was a significant increase in RJT (from 31.6±2.8–54.5±28.3 N-m;/K0.001). CONCLUSIONS: The method developed by Rosenbaum and Gregory (2002) and validated by Gregory (2004) appears to be suitable for evaluating the effects of load on muscular effort during single-joint, upper-extremity movements. This method may be useful for both clinical and basic research attempting to examine the biomechanics of muscular effort. In addition, this study supports the assumption that sense of effort is most directly related to joint torque (Andrews, 1981). This investigation was supported by the University of Kansas General Research Fund allocation #2301758.