Movement of loads with trunk rotation

Movements with participants standing at a bench and moving loads up to 6 kg were studied, with participants using two hands to hold the load and trunk rotation in order to move the loads to specified locations. Tasks were performed with rapid ballistic movements and also with ongoing visual control. Data for ballistic movements were modelled in terms of a modified form of the (Gan, K.-C. and Hoffmann, E.R. 1988. “Geometrical conditions for ballistic and visually controlled movements.” Ergonomics 5 (31): 829–839) model for ballistic movements, taking into account the inertial properties of trunk rotation. Visually-controlled movements were modelled in terms of Fitts' law and a term that allowed for the ballistic form of the first submovement of the visually-controlled movement.

Practitioner Summary: Movement times to move masses up to 6 kg, for workers at a bench using trunk rotation, are given. Theoretical models fit the experimental data very well and allow prediction of movement times.     

Restriction to movement in fire-fighter protective clothing: evaluation of alternative sleeves and liners

The purpose of this study was to evaluate alternative designs and liner configurations in fire-fighter protective clothing, or 'turnout gear', to determine the restriction to wearer movement imposed by each. The independent variables were: (1) two alternative sleeve designs (i e, a 'traditional' sleeve design and a prototype sleeve design, featuring additional gusset width and altered armseye position) plus a station uniform worm without any protective clothing and/or equipment; (2) three liner configuration variations (i e, a 'traditional' liner configuration, incorporation of one additional liner, and incorporation of two additional liners); and (3) wearing or not wearing an SCBA (self-contained breathing apparatus). The dependent variables for this study were: (1) range of movement in four upper body joints; and (2) a semantic differential scale to evaluate wearers' subjective evaluation of each protective ensemble. Nine male subjects were used. For each of the four joint movements measured (i e, shoulder flexion/extension, shoulder adduction/abduction, shoulder rotation, elbow flexion/extension), a Leighton Flexometer was strapped to the subject at the appropriate body location. The subject was instructed to take the body position indicated. A reading was taken, then the subject was asked to move the body segment to the fullest extent possible in the direction indicated by the researcher. A second reading (representing range of movement) was taken. This procedure was repeated three times for each movement. After the test, subjects were instructed to fill out a semantic differential scale which described their subjective evaluations of the clothing/ equipment configuration. Results showed greater wearer range of movement in the elbow area for the prototype sleeve design over the more traditional sleeve design. Incorporation of additional liners resulted in higher wearer acceptability for the turnout coats than when these liners were not used. As expected, use of an SCBA was extremely restrictive to mobility, and made the protective ensemble less acceptable to wearers.     

Modeling the Influences of Cyclic Top-Down and Bottom-Up Processes for Reinforcement Learning in Eye Movements

Understanding and reproducing complex human oculomotor behaviors using computational models is a challenging task. In this paper, two studies are presented, which focus on the development and evaluation of a computational model to show the influences of cyclic top-down and bottom-up processes on eye movements. To explain these processes, reinforcement learning was used to control eye movements. The first study showed that, in a picture-viewing task, different policies obtained from different picture-viewing conditions produced different types of eye movement patterns. In another visual search task, the second study illustrated that feedback information from each saccadic eye movement could be used to update the model's eye movement policy, generating different patterns in the following saccade. These two studies demonstrate the value of an integrated reinforcement learning model in explaining both top-down and bottom-up processes of eye movements within one computational model.     

Different predictions by the minimum variance and minimum torque-change models on the skewness of movement velocity profiles

We investigated the differences between two well-known optimization principles for understanding movement planning: the minimum variance (MV) model of Harris and Wolpert (1998) and the minimum torque change (MTC) model of Uno, Kawato, and Suzuki (1989). Both models accurately describe the properties of human reaching movements in ordinary situations (e.g., nearly straight paths and bell-shaped velocity profiles). However, we found that the two models can make very different predictions when external forces are applied or when the movement duration is increased. We considered a second-order linear system for the motor plant that has been used previously to simulate eye movements and single-joint arm movements and were able to derive analytical solutions based on the MV and MTC assumptions. With the linear plant, the MTC model predicts that the movement velocity profile should always be symmetrical, independent of the external forces and movement duration. In contrast, the MV model strongly depends on the movement duration and the system's degree of stability; the latter in turn depends on the total forces. The MV model thus predicts a skewed velocity profile under many circumstances. For example, it predicts that the peak location should be skewed toward the end of the movement when the movement duration is increased in the absence of any elastic force. It also predicts that with appropriate viscous and elastic forces applied to increase system stability, the velocity profile should be skewed toward the beginning of the movement. The velocity profiles predicted by the MV model can even show oscillations when the plant becomes highly oscillatory. Our analytical and simulation results suggest specific experiments for testing the validity of the two models.     

Office task effects on comfort and body dynamics in five dynamic office chairs

In the present study, we investigated the effect of office tasks on posture and movements in field settings, and the comfort rating for chair characteristics and correlation with type of task. The tasks studied were: computer work, telephoning, desk work and conversation. Postures, movements, chair part inclinations and comfort rating data were collected from 12 subjects. Computer work showed the lowest physical activity, together with upright trunk and head position and low backrest inclination. Conversation shows the highest activity of head legs and low back together with the highest cervical spine extension. In contrast, desk work provoked the most cervical spine flexion and showed the second lowest activity. The telephoning tasks showed medium activity and the highest kyphosis. Conversation showed the highest backrest inclination. Positive comfort relations were found for computer work and a "swing system" chair, for telephoning and an active longitudinal seat rotation, and for desk work and a chair with a three-dimensionally moveable seat.     

A cascaded scheme for eye tracking and head movement compensation

The authors previously (1995) proposed an efficient method for tracking the eye movements. The proposed algorithm did not address the issue of compensating for head movements. Head movements are normally much slower than eye movements and can be compensated for using another tracking scheme for head position. In this paper, a hybrid method employing the two tracking schemes is developed. To this end, first a measurement model for the compensation of the head movement is formulated and then the overall tracking scheme is implemented by cascading two Kalman filters. The tracking of the iris movement is followed by the compensation of the head movement for each image frame. Experimental results are presented to demonstrate the accuracy aspects and the real-time applicability of the proposed approach     

Verification of models for ballistic movement time and endpoint variability

A hand control movement is composed of several ballistic movements. The time required in performing a ballistic movement and its endpoint variability are two important properties in developing movement models. The purpose of this study was to test potential models for predicting these two properties. Twelve participants conducted ballistic movements of specific amplitudes using a drawing tablet. The measured data of movement time and endpoint variability were then used to verify the models. This study was successful with Hoffmann and Gan's movement time model (Hoffmann, 1981; Gan and Hoffmann 1988) predicting more than 90.7% data variance for 84 individual measurements. A new theoretically developed ballistic movement variability model, proved to be better than Howarth, Beggs, and Bowden's (1971) model, predicting on average 84.8% of stopping-variable error and 88.3% of aiming-variable errors. These two validated models will help build solid theoretical movement models and evaluate input devices.

Practitioner summary: This article provides better models for predicting end accuracy and movement time of ballistic movements that are desirable in rapid aiming tasks, such as keying in numbers on a smart phone. The models allow better design of aiming tasks, for example button sizes on mobile phones for different user populations.     

Three-dimensional spinal motion and risk of low back injury during sheep shearing

Sheep shearers are known to work in sustained flexed postures and have a high prevalence of low back pain (LBP). As sustained posture and spinal movement asymmetry under substantial loads are known risk factors for back injury our aim was to describe the 3D spinal movement of shearers while working. We hypothesised that thoraco-lumbar and lumbo-sacral movement would be tri-axial, asymmetric, and task specific. Sufficient retro-reflective markers were placed on the trunk of 12 shearers to define thoraco-lumbar and lumbo-sacral 3D motion during three tasks. Thoraco-lumbar movement consistently involved flexion, left lateral flexion, and right rotation. Lumbo-sacral movement consistently involved right lateral flexion in flexion with minimal rotation. Shearers therefore work in sustained spinal flexion where concurrent, asymmetric spinal movements into both lateral flexion and rotation occur. These asymmetric movements combined with repetitive loading may be risk factors leading to the high incidence of LBP in this occupational group.     

Effect of heliotropism on the bidirectional reflectance of irrigated cotton

The dynamic movement of cotton leaves in the presence of sunlight has been described using gyroscopic coordinates. These coordinates were used to calculate the position of leaf normals with respect to the sun on an individual basis. A sensitivity analysis established that the angle between a leaf normal and the sun was most affected by changes in pitch and roll. Averaging leaf normals by quadrant (as established by the direction of the compass) showed the pronounced heliotropic behavior of cotton leaves and the differential behavior of cotton leaves relative to the quadrant of the sun. These results were subsequently applied to the estimation of the phase angle γ between the canopy normals and sun from cross sections of bidirectional reflectance curves obtained for a band spanning 0.57–0.69 μm. From the cross section determined by the principal plane at 6:07 MST, which turned out to be concave and nearly symmetrical, the canopy averaged value for γ was estimated to be about 90°, while the calculated value from the leaf angle data was 85°. At 12:08 MST the same cross section was convex and asymmetrical with respect to rotation about the nadir direction, indicating distinguishable forescattered and backscattered components. For the forescattered component the estimated value for γ was 15°, and the calculated value 20°. For the backscattered component the estimated value for γ was 12°, and the calculated value 21°. These results suggested that bidirectional reflectance information analyzed sequentially using a visible band for which the optical transmission is nearly zero can be used to monitor leaf movement and hence moisture availability.     

Evaluation of document location during computer use in terms of neck muscle activity and neck movement

This study evaluated the impact on neck movement and muscle activity of placing documents in three commonly used locations: in-line, flat desktop left of the keyboard and laterally placed level with the computer screen. Neck excursion during three standard head movements between the computer monitor and each document location and neck extensor and upper trapezius muscle activity during a 5 min typing task for each of the document locations was measured in 20 healthy participants. Results indicated that muscle activity and neck flexion were least when documents were placed laterally suggesting it may be the optimal location. The desktop option produced both the greatest neck movement and muscle activity in all muscle groups. The in-line document location required significantly more neck flexion but less lateral flexion and rotation than the laterally placed document. Evaluation of other holders is needed to guide decision making for this commonly used office equipment.     

机动目标运动模型动态辨识理论的研究

在对现有机动目标假定模型结构的合理性及现代战场对目标模型需求性综合分析的基础上，完成了机动目标运动模型的辨识理论研究，提出了机动目标运动模型可动态辨识的条件．为解决机动目标运动模型动态辨识提供了新的技术途径．所提出的“参数辨识模型”具有良好的模型结构，对目标的各种运动模态具有广泛的适应能力．     

Intra-articular kinematics of the upper limb joints: a six degrees of freedom study of coupled motions

In sport, leisure and certain occupational activities, joint lesions of the upper limb are very common. To understand their aetiology in order to prevent and treat these pathologies on a scientific basis, a comprehensive knowledge of the involved stress and kinematics is imperative. For many years intra-articular joint kinematics have been described hypothetically in terms of the convex-concave principle. This principle, however, has not been validated. The in vitro research on the acromioclavicular, glenohumeral and elbow joints was performed using an electromagnetic tracking device (Flock of Birds). By recalculating the positions of the trackers to an embedded coordinate system on the joint surface, the intra-articular joint movements can be analysed. Therefore, the bony configurations and articular surface features were registered with a 3D drawing stylus (Microscribe). Thirteen acromioclavicular joints, six glenohumeral joints and seven elbows were studied. The coupled intra-articular movements were analysed using the Euler angles and finite helical axis approaches. The results of the acromioclavicular joint analysis indicate that during movements in the scapular plane a superior rotation of the clavicle was coupled with an inferior translation and vice versa, whilst during movements in the plane perpendicular to the scapular plane the anterior rotation was coupled with an anterior translation and vice versa. In the glenohumeral joint, the abduction-elevation was coupled with an external rotation. In the humero-ulnar joint, the extension was coupled with an external rotation and varus movement. This intra-articular behaviour was in contradiction to currently accepted convex-concave concepts in arthrokinematics and manual therapy. The results may have major implications for manual therapy and orthopaedic medical practice.     

基于循环神经网络的空载电动出租车的充电桩推荐方法

提出了一种基于循环神经网络的空载电动出租车的充电桩推荐方法（CPRM-IET,charging pile recommendation method for idle electric taxis）,来为空载状态下的电动出租车推荐最佳充电桩。空载状态下的电动出租车移动一般依赖于驾驶人的潜意识移动倾向和驾驶习惯,因此需要根据其历史移动轨迹来预测其未来移动,从而找到充电额外移动最小的若干充电桩。在CPRM-IET中,使用了一种基于双阶段注意力机制的循环神经网络（DA-RNN,dual-stage attention-based recurrent neural network）模型来预测电动出租车的未来轨迹,DA-RNN模型包括输入注意力机制和时间注意力机制。输入注意力机制在每个时刻为输入的行驶记录分配权重,而时间注意机制为编码器的隐藏状态分配权重。根据预测轨迹,再选择额外移动最小的若干充电桩,并推荐给电动出租车驾驶人。仿真结果表明,CPRM-IET可以在额外移动和均方根误差方面取得较好的结果,反映了CPRM-IET可以准确地预测空载电动出租车的未来轨迹,并向这些电动出租车推荐合适的充电桩。     

Evaluation of eye,head and trunk coordination during target tracking tasks

This study tested the feasibility of a method to synchronise and to evaluate eye, head and trunk movement patterns during target tracking tasks performed by 10 subjects. A projected central target was randomly repositioned at 40° and 70° of rotation to the left and right. Subjects were instructed to change gaze as quickly as possible. Head and trunk motion was measured using a motion analysis system, and eye movement was measured using an eye-tracker; all data were synchronised. For healthy subjects, the eye moved faster than the head, there was no trunk movement and the head moved more than the eye to reach further displaced targets. The method tested was feasible, and it could be used to evaluate eye, head and trunk movement patterns of subjects with injuries such as whiplash and concussions.

Practitioner Summary: Studies of eye, head and trunk movements using synchronised methods are needed. We tested the feasibility of a method to synchronise and evaluate eye, head and trunk movement patterns. The method tested was feasible, and it could be used to evaluate movement patterns of subjects with injuries such as whiplash.     

Strengths and limitations of a musculoskeletal model for an analysis of simulated meat cutting tasks

This study assessed the capacity of a musculoskeletal model to predict the relative muscle activation changes as a function of the workbench height and the movement direction during a simulated meat cutting task. Seven subjects performed a cutting task alternating two cutting directions for 20 s at four different workbench heights. Kinematics, electromyography (EMG), and cutting force data were collected and used to drive a musculoskeletal model of the shoulder girdle. The model predicted the muscle forces exerted during the task. Both the recorded and computed activation of the muscles was then compared by means of cross-correlation and by comparison of muscle activation trends with respect to the workstation parameters, i.e. cutting direction and workbench height. The results indicated that cutting movements involving arm flexion are preferable to movement requiring internal arm rotation and abduction. The optimal bench height for meat cutting tasks should be between 20 and 30 cm below the worker's elbow height. The present study underlines a beneficial use of musculoskeletal models for adjusting workstation parameters.     

Enhanced avatar control using neural networks

This paper presents realistic avatar movements using a limited number of sensors. An inverse kinematics algorithm, SHAKF, is used to configure an articulated skeletal model, and a neural network is employed to predict the movement of joints not bearing sensors. The results show that the neural network is able to give a very close approximation to the actual rotation of the joints. This allows a substantial reduction in the number of sensors to configure an articulated human skeletal model.     

Velocity and pressure-based partitions of horizontal and vertical trajectories for on-line signature verification

In general, shape of an on-line signature is used as a single discriminating feature. Sometimes shape of signature is used alone for verification purposes and sometimes it is used in combination with some other dynamic features such as velocity, pressure and acceleration. The shape of an on-line signature is basically formed due to the wrist and fingers movements where the wrist movement is represented by the horizontal trajectory and the movement of the fingers is represented by vertical trajectory. As the on-line signature is formed due to the combination of two movements that are essentially independent of each other, it will be more effective to use them as two separate discriminating features. Based on this observation, we propose to use these trajectories in isolation by first decomposing the pressure and velocity profiles into two partitions and then extracting the underlying horizontal and vertical trajectories. So the overall process can be thought as the process which exploits the inter-feature dependencies by decomposing signature trajectories depending upon pressure and velocity information and performs verification on each partition separately. As a result, we are able to extract eight discriminating features and among them the most stable discriminating feature is used in verification process. Further Principal Component Analysis (PCA) has been proposed to make the signatures rotation invariant. Experimental results demonstrate superiority of our approach in on-line signature verification in comparison with other techniques.     

Effectiveness of leg movement in reducing leg swelling and discomfort in lower extremities

Various occupations required that workers stand for long periods, causing discomfort and pain. This study considered the effectiveness of three leg movements in relieving discomfort of the lower extremities during long periods of standing at work. Ten paid male subjects with no history of problems of the lower extremities were enrolled in this study. They performed three leg movements on a hard floor while standing for 4 h in a laboratory setting. Each 1 h experimental test had two phases - 50 min of standing, followed by 10 min of rest. During the period of standing, one the following leg movements was made. No movement (no change in posture), ankle movement (twice, for 2 min each time), and hip movement (twice, for 2 min each time). Observations revealed that the three leg movements yielded different degrees of lower limb swelling. The percentage changes in thigh (1.22%) and shank (1.32%) circumferences were largest during prolonged standing without any movement and lowest during prolonged standing with ankle movement (0.61%) and hip movement (0.80%). The relationship between perceived discomfort and standing time was determined. The subjects perceived the most shank discomfort (5.8) during the 4 h test without any movement. Leg movement greatly influenced perceived discomfort of the shank. The results of this study suggested that workers should move their ankles and hips for a short period following prolonged standing for 30 min to reduce lower extremity discomfort.     

Goal-directed aimed movements with path obstructions

Studies are reported in which participants moved from a starting position to a final target, but moved around obstacles that prevented a direct path being taken. Seven experiments are reported in which subjects made multiple-component movements, defined by changes in the direction of movement, but without intervening targets (or stopping points) between components. It was found that components of movement time did not interact, contrary to the results of Gan and Hoffmann (1988b) for cases where there was an intervening target, and that component times could be added. For ballistic components, the time for the movement was linearly related to the square root of the total amplitude of movement; for components that were visually controlled, the time was related to Fitts' Index of Difficulty based on the total amplitude of movement and the final target size. Results are compared to data for movements with intervening targets, where the movement integration hypothesis is valid. PRACTITIONER SUMMARY: Many movements, particularly to inaccessible places, cannot be made directly, but must be made about obstacles in the path. This research shows how times for these movements can be quantified in terms of the direct path length and the size and location of the obstacles.     

Spatial compatibility effects with tool use

OBJECTIVE: We explored constraints in responding to spatially variable stimuli when hand movements are transformed into inverse movements of a tool. BACKGROUND: Generally, the spatial compatibility between stimuli and responses is a powerful determinant of performance. However, many tasks require the use of simple tools such as first-class levers that transform hand movements into inverted movements of a tool. What types of compatibility effects arise with such tools? METHOD: Participants moved the tip of a pointer to the left or right according to the color of a stimulus. The pointer was manipulated either directly, so that a hand movement caused a pointer movement in the corresponding direction, or indirectly, so that the hand moved the pointer in the opposite direction. RESULTS: Responding was faster when the location of stimulus and the movement direction of the tool corresponded than when they did not correspond, independent of the movement direction of the hand. This occurred when stimulus location was task relevant (Experiment 1) as well as when it was task irrelevant (Experiment 2). Furthermore, responding was delayed when the hand and the relevant end of the tool moved in noncorresponding rather than corresponding directions. CONCLUSION: These results point to two distinct compatibility effects in tool use: one that relates to the transformation of stimuli into goals and one that relates to the transformation of goals into movements. APPLICATION: Potential applications of this research include the prediction and possibly manipulation of unwanted "fulcrum effects" in laparoscopic surgery and other first-class lever movements.