Carrying a rifle with both hands affects upper body transverse plane kinematics and pelvis-trunk coordination

The purpose of this study was to assess how carrying a rifle in both hands affects upper body motion and coordination during locomotion. In total, 11 male soldiers walked (1.34 m/s) and ran (2.46 m/s) with a weapon (M4 condition) and without a weapon (NW condition) while kinematic pelvis and trunk data were collected. Two-way ANOVA was used to compare segmental ranges of motion (ROM), pelvis-trunk coordination (continuous relative phase) and coordination variability between gait mode and weapon combinations. Carrying a weapon decreased sagittal plane trunk ROM at both speeds and increased trunk rotation during running. Mean (±SD) transverse plane coordination was more in-phase while carrying a weapon (M4 = 83°±31, NW = 60°±36, p = 0.027) and transverse plane coordination variability decreased (M4 = 23°±3.6, NW = 15°±4.4, p = 0.043). Coordination differences between M4 and NW were similar to differences reported in the literature between individuals with and without back pain. Long-term injury implications due to decreased coordination variability are discussed. STATEMENT OF RELEVANCE: Knowledge of the effects of rifle carriage on pelvis-trunk coordination may provide insight into short-term protective strategies and long-term injury mechanisms. These should be considered in occupations requiring individuals to carry torso loads in combination with holding an object in both hands that restricts arm swing.     

Analytically derived three-dimensional reach volumes based on multijoint movements

The main objectives of this study were to quantify the range of reaching for the upper body with eight degrees of freedom (the trunk and shoulder, elbow, and wrist joints) and the lower body with six degrees of freedom (the hip, knee, and ankle joints). A sweeping algorithm that included trunk and foot motions was used to generate the analytical total reach volume of the human body for young men. Three types of reach volume--unconstrained arm reach, shoulder-restricted arm reach, and foot reach--were generated depending on the joint involved in reach activities. The robot kinematics methodology was employed to represent the human body as a multilink system, which was needed for calculating three-dimensional coordinates of the involved joints. The statistical test results showed that the total reach volume analytically generated in this study was nearly identical to that obtained from the direct human body measurements. Applications of this research include generating the human body's reach volume for the purpose of designing work spaces and products.     

Hand-hold location and trunk kinematics during box handling

Trunk kinematics variables have been shown to be related to low back injury risk during lifting tasks and it was hypothesised that changes in hand-hold positions could influence trunk kinematics and thereby risk. Fourteen subjects lifted a 5 or 10 kg box using four different hand placement locations (two symmetric and two asymmetric) while their trunk kinematics (position, velocity and acceleration in the sagittal, coronal and transverse planes) were captured using the lumbar motion monitor (LMM). These kinematics data were then used to calculate the probability of high risk group membership (PHRGM) as defined in the LMM risk assessment model. The results showed significant effects of hand placement on trunk kinematics, resulting in significant changes in the PHRGM variable ranging from a low of 20% in a the symmetric low load condition to a high of 38% under the asymmetric, 10 kg condition.

Statement of Relevance: Manual materials handlers use a variety of hand-hold positions on boxes during lifting. Where a lifter grabs the box can influence the trunk kinematics during the lifting task and these kinematics have been shown to provide some insight into risk of low back injury. This study documents the trunk postures and kinematics as a function of hand-hold position.     

Multi-segment trunk kinematics during a loaded lifting task for elderly and young subjects

The trunk is frequently modelled as one fixed segment ignoring possible multi-segmental contributions during manual handling. This study compared segmental trunk motion in a young and older population during a lifting task. Twelve elderly and 19 young subjects repeatedly lifted a 5 kg box from bench to shelf under two stance conditions. Displacement and angular trunk segment kinematics were recorded with an electromagnetic tracker system and then analysed. The elderly subjects displayed significantly increased pelvic and trunk displacement and significantly reduced pelvic and lower thorax (T10–L1) range of motion in both stance conditions. Upper thorax (C7–T10) motion was at times greater than lumbar motion and opposite to the lower segments and was related to the task while the lower segments contributed to both equilibrium and task requirements. Decreased segmental trunk angular kinematics may contribute to increased displacement kinematics and place the elderly at increased risk of injury and falling. The pelvis, lumbar spine, low thorax (T10–L1), upper thorax (C7–10) contributed uniquely and synchronously to trunk (C7–S2) mechanics during a lifting task. Reduced angular kinematics of the pelvis and low thorax contributed to increased displacement kinematics and hence increased the risk of falling in the elderly compared to the young. Investigations of trunk mechanics should include multi-segment analysis.     

Effects of age, gender, and target location on seated reach capacity and posture

OBJECTIVE: The aim of this study was to investigate the effects of age, gender, and target location upon arm reach capacity and posture. BACKGROUND: The older adult population is growing in number. Their specific needs must be better understood to improve the design of work and life spaces. METHOD: Thirty-eight adults, divided into four groups according to their gender and age, participated in the experiment. They were asked to reach 84 targets located in a large space defined according to their anthropometry and reach capacities. Reach capacities and postures were analyzed. RESULTS: On average, older participants showed shorter maximal reach distances (by 4.8% of upper limb length) as compared with younger participants. No gender difference was found for maximum reach distance. Age also had significant effects on reach posture, especially through its interactions with target azimuth. Older participants tended to use their trunk less whenever possible. Reduced neck and trunk/seat axial rotations were observed for the older participants when the target deviated from the sagittal plane. They compensated by a greater rotation of the pelvis with respect to the seat. CONCLUSION: Older people's reach capacities should be taken as references, rather than those of younger people, in order to accommodate a wider range of the population. APPLICATION: These results can be used to improve the arrangement of living spaces and work spaces for older people.     

Effect of foot movement and an elastic lumbar back support on spinal loading during free-dynamic symmetric and asymmetric lifting exertions

The aim of this study was to assess the effect of an elastic lumbar back support on spinal loading and trunk, hip and knee kinematics while allowing subjects to move their feet during lifting exertions. Predicted spinal forces and moments about the L5/S1 intervertebral disc from a three-dimensional EMG-assisted biomechanical model, trunk position, velocities and accelerations, and hip and knee angles were evaluated as a function of wearing an elastic lumbar back support, while lifting two different box weights (13.6 and 22.7 kg) from two different heights (knee and 10 cm above knee height), and from two different asymmetries at the start of the lift (sagittally symmetric and 60 degrees asymmetry). Subjects were allowed to lift using any lifting style they preferred, and were allowed to move their feet during the lifting exertion. Wearing a lumbar back support resulted in no significant differences for any measure of spinal loading as compared with the no-back support condition. However, wearing a lumbar back support resulted in a modest but significant decrease in the maximum sagittal flexion angle (36.5 to 32.7 degrees), as well as reduction in the sagittal trunk extension velocity (47.2 to 40.2 degrees s(-1)). Thus, the use of the elastic lumbar back support provided no protective effect regarding spinal loading when individuals were allowed to move their feet during a lifting exertion.     

Trunk kinematics of one-handed lifting,and the effects of asymmetry and load weight

Abstract

This study investigated trunk kinematic differences between lifts performed using either one hand (unsupported) or two hands. These effects were studied while beginning the lifts from different asymmetric starting positions and while lifting different load weights. Each subject lifted a box from a lower to an upper platform under one- and two-handed lifting conditions. Subjects wore a lumbar spine electrogoniometer, from which relative motion components were calculated in the trunk's three cardinal planes. Results of this study showed that one-handed lifting resulted in significantly higher ranges of motion in the lateral and transverse planes and greater flexion in the sagittal plane. Back motion characteristics previously found to be associated with low back disorders were all significantly higher for one-handed lifts. The two-handed lift technique, on the other hand, produced overall faster trunk motions in the sagittal plane and equal or larger acceleration and deceleration magnitudes in all planes of motion. Increases in load asymmetry affected trunk kinematics, in that magnitude values for range of motion, velocity and acceleration became much greater with increasingly asymmetric load positions. Increasing the load weight appeared to have less of an effect on trunk kinematics, with increases in position mostly occurring during sagittal and lateral bending. These results suggest that unsupported one-handed lifting loads the spine more than two-handed lifts, due to the added coupling. Applying these results to a previously developed model, one-handed lifting was also found to increase one's risk of suffering a low back disorder.     

Effect of foot movement and an elastic lumbar back support on spinal loading during free-dynamic symmetric and asymmetric lifting exertions

The aim of this study was to assess the effect of an elastic lumbar back support on spinal loading and trunk, hip and knee kinematics while allowing subjects to move their feet during lifting exertions. Predicted spinal forces and moments about the L5/S1 intervertebral disc from a three-dimensional EMG-assisted biomechanical model, trunk position, velocities and accelerations, and hip and knee angles were evaluated as a function of wearing an elastic lumbar back support, while lifting two different box weights (13.6 and 22.7 kg) from two different heights (knee and 10 cm above knee height), and from two different asymmetries at the start of the lift (sagittally symmetric and 60°asymmetry). Subjects were allowed to lift using any lifting style they preferred, and were allowed to move their feet during the lifting exertion. Wearing a lumbar back support resulted in no significant differences for any measure of spinal loading as compared with the no-back support condition. However, wearing a lumbar back support resulted in a modest but significant decrease in the maximum sagittal flexion angle (36.5 to 32.7°), as well as reduction in the sagittal trunk extension velocity (47.2 to 40.2°s^-1). Thus, the use of the elastic lumbar back support provided no protective effect regarding spinal loading when individuals were allowed to move their feet during a lifting exertion.     

Effect of the presence or absence of upper limb support on posture when a smartphone user is in a seated position under ambient light conditions

BackgroundHome, public transport, work, the number of environmental positions constraining the use of smartphones is significant.Research questionHow can the presence of an upper limb support influence the sitting posture of smartphone users under fixed illumination and brightness?MethodsTwelve subjects (21,6 ± 5,5 years old) performed web browsing under two environmental positions (POSITION): sitting with and without support (table). The users' postures were evaluated through relative kinematics joint angles analysis. A repeated measure analysis of variance and Tukey post-hoc tests were performed to test the effect of POSITION on posture.ResultsIn sitting position in front of a table, neck is less stressed (flexion < 10°) and trunk and shoulder are supported which suggests less constrains for the joints.Relevance to industryTo prevent injury or pain, the use of an upper limb support (to lean on) should be considered for people/workers who use the smartphone frequently.     

Wrist postures in the general population of computer users during a computer task

Computer activities have commonly been linked to the development of musculoskeletal disorders (MSDs) in the upper limbs. However, to understand the effects computer use has on such disorders, it is necessary to identify and classify the movements involved in performing common computer tasks, one of these being typing. Motion analysis techniques were adopted to determine the movements involved during a typing task. This involved markers being placed on the knuckles, wrists and forearms of participants. This marker configuration allowed for the flexion, extension, radial deviation, ulnar deviation and a combination of these movements to be calculated. The results in one plane of motion show a mean extension|flexion and radial|ulnar deviation of 18.825°?±?10.013° and 5.228°?±?11.703° respectively. The most common position in two planes of motion was 20° extension with a simultaneous 20° ulnar deviation (10.72%). The results depict an alternative method of categorizing wrist positions in two planes during computer use. Coincident wrist postures should be addressed as opposed to motion in a single plane as these postures may result in different ergonomic risk factors developing.     

The effects of military body armour on trunk and hip kinematics during performance of manual handling tasks*

Musculoskeletal injuries are reported as burdening the military. An identified risk factor for injury is carrying heavy loads; however, soldiers are also required to wear their load as body armour. To investigate the effects of body armour on trunk and hip kinematics during military-specific manual handling tasks, 16 males completed 3 tasks while wearing each of 4 body armour conditions plus a control. Three-dimensional motion analysis captured and quantified all kinematic data. Average trunk flexion for the weightiest armour type was higher compared with control during the carry component of the ammunition box lift (p?<?0.001) and sandbag lift tasks (p?<?0.001). Trunk rotation ROM was lower for all armour types compared with control during the ammunition box place component (p?<?0.001). The altered kinematics with body armour occurred independent of armour design. In order to optimise armour design, manufacturers need to work with end-users to explore how armour configurations interact with range of personal and situational factors in operationally relevant environments.

Practitioner Summary: Musculoskeletal injuries are reported as burdening the military and may relate to body armour wear. Body armour increased trunk flexion and reduced trunk rotation during military-specific lifting and carrying tasks. The altered kinematics may contribute to injury risk, but more research is required.     

A SVM controller for the stable walking of biped robots based on small sample sizes

Conventional machine learning methods such as neural network (NN) uses empirical risk minimization (ERM) based on infinite samples, which is disadvantageous to the gait learning control based on small sample sizes for biped robots walking in unstructured, uncertain and dynamic environments. Aiming at the stable walking control problem in the dynamic environments for biped robots, this paper puts forward a method of gait control based on support vector machines (SVM), which provides a solution for the learning control issue based on small sample sizes. The SVM is equipped with a mixed kernel function for the gait learning. Using ankle trajectory and hip trajectory as inputs, and the corresponding trunk trajectory as outputs, the SVM is trained based on small sample sizes to learn the dynamic kinematics relationships between the legs and the trunk of the biped robots. Robustness of the gait control is enhanced, which is propitious to realize the stable biped walking, and the proposed method shows superior performance when compared to SVM with radial basis function (RBF) kernels and polynomial kernels, respectively. Simulation results demonstrate the superiority of the proposed methods.     

A study of lifting tasks performed on laterally slanted ground surfaces

Lifting in most industrial environments is performed on a smooth, level ground surface. There are, however, many outdoor work environments (e.g. agriculture and construction) that require manual material handling activities on variable grade ground surfaces. Quantifying the biomechanical response while lifting under these conditions may provide insight into the aetiology of lifting-related injury. The aim of the current study was to quantify the effect of laterally slanted ground surfaces on the biomechanical response. Ten subjects performed both isometric weight-holding tasks and dynamic lifting exertions (both using a 40% of max load) while standing on a platform that was laterally tilted at 0, 10, 20 and 30 degrees from horizontal. As the subject performed the isometric exertions, the electromyographic (EMG) activity of trunk extensors and knee extensors were collected and during the dynamic lifting tasks the whole body kinematics were collected. The whole body kinematics data were used in a dynamic biomechanical model to calculate the time-dependent moment about L5/S1 and the time-dependent lateral forces acting on the body segments. The results of the isometric weight-holding task show a significant (p < 0.05) effect of slant angle on the normalized integrated EMG values in both the left (increase by 26%) and right (increase by 70%) trunk extensors, indicating a significant increase in the protective co-contraction response. The results of the dynamic lifting tasks revealed a consistent reduction in the peak dynamic L5/S1 moment (decreased by 9%) and an increase in the instability producing lateral forces (increased by 111%) with increasing slant angle. These results provide quantitative insight into the response of the human lifter under these adverse lifting conditions.     

Effects of age and gender on maximum voluntary range of motion of the upper body joints

The maximum voluntary range of motion (ROM) of the major joints of the upper body was studied in a seated position and compared between young and elderly subjects. A total of 41 subjects (22 young male and female subjects aged 25 to 35 years, 19 elderly male and female subjects aged 65 to 80 years) took part in the experiment. In total, 13 maximum voluntary joint motions were performed by each subject. Age was found to have a non-uniform effect on the ROM of the joints investigated in this study. Its effect on ROM was joint specific and motion specific. The highest loss in ROM was observed in the neck and trunk, especially for neck extension, lateral flexion and axial rotation as well as for trunk lateral flexion and axial rotation. No significant age differences were observed in the elbow and wrist joint ROMs. The effect of gender on joint ROM was much weaker than that of age. Only four among the 26 joint ROMs investigated in this study were significantly different between the two gender groups.     

Effects of age and gender on maximum voluntary range of motion of the upper body joints

The maximum voluntary range of motion (ROM) of the major joints of the upper body was studied in a seated position and compared between young and elderly subjects. A total of 41 subjects (22 young male and female subjects aged 25 to 35 years, 19 elderly male and female subjects aged 65 to 80 years) took part in the experiment. In total, 13 maximum voluntary joint motions were performed by each subject. Age was found to have a non-uniform effect on the ROM of the joints investigated in this study. Its effect on ROM was joint specific and motion specific. The highest loss in ROM was observed in the neck and trunk, especially for neck extension, lateral flexion and axial rotation as well as for trunk lateral flexion and axial rotation. No significant age differences were observed in the elbow and wrist joint ROMs. The effect of gender on joint ROM was much weaker than that of age. Only four among the 26 joint ROMs investigated in this study were significantly different between the two gender groups.     

Physical demands of overhead crane operation

Recent studies have suggested that ergonomic factors may contribute to risks experienced by overhead crane operators. However, there are few studies that provide a comprehensive overview of the physical demands of overhead crane operation. This study aimed to provide this information by quantifying muscular, postural, and upper limb movement demands of overhead crane operation including examination of muscle activation and trunk posture by task. Trunk posture, upper limb movement demands and muscle activation in the trunk and upper limbs were quantified for seven overhead crane operators. Trunk posture was quantified using trunk angle and joystick motion requirements were determined using camera data. Muscle activation was measured bilaterally using surface EMG for the upper trapezii, anterior deltoids, posterior deltoids, biceps brachii, triceps brachii, flexor carpi radialis and erector spinae. Lastly, joystick force requirements were assessed using a spring scale. High upper limb and trunk muscle loading were observed when compared to joystick use in other heavy machinery, in part due to the forward, trunk-flexed position required to adequately view the workspace, and the increased force requirements of the joysticks. Joystick input force requirements were 9–31 N for the right-hand joystick and 11–40 N for the left-hand joystick. Operators maintained a forward trunk flexion (>20°) for all subtasks which suggests that trunk posture might play a role in sustained trunk muscle activation. Results suggest that the primary issue with overhead crane cab operation is upper limb and trunk muscle loading. Results confirm the need to investigate muscle load reduction strategies such as camera systems to help reduce the need for trunk flexion. Other design modification suggestions include reducing the joystick input force and displacement requirements coupled with potentially distributing the machine functions more evenly across the right and left controllers.     

微传感器测量运动状态下的人体躯干倾角

精确地测量与控制躯干部的姿态对于人体和仿人机器人的运动学研究具有重要意义。先前的研究大多基于泛用算法,实验条件单一。基于陀螺仪和磁力计的数据融合,提出了一种用于估算运动状态下人体躯干倾角的算法。实验结果表明：在不同运动状态下,算法的均方根误差为1.81°±0.77°。该算法可以应用在有关人体和机器人运动平衡性的研究中。     

Analytic generation of workspace using the robot kinematics

When designing workplaces, controls should be placed within the reach of an operator's arm or foot for guaranteeing effective performance. In designing a workplace which must cater to a wide range of operator size, it might be sufficient to plan only for the ‘average person’. Static arm reach measurements which are taken in conventional, standardized positions provide necessary information, but they cannot be applied to dynamic situations directly. To obtain reach envelope or workspace of the human body not by direct measurement but by analytic generation, data on range of joint motion(ROM) are required as an input. The purposes of this research are to measure the range of motion of two degrees of freedom for Korean young males, and to propose an approximate algorithm to generate the workspace of the human body including foot and trunk motion, in which joint mobility of two degrees of freedom motion are considered. The robot kinematics was employed to represent the human body as a multi-link system.