Effects of the abdominal belt on muscle-generated spinal stability and L4/L5 joint compression force

The goals of this study were (1) to determine the effects of abdominal belts on muscle-generated active lumbar spine stability, (2) to determine their effect on the subsequent joint compression force at L4/L5 and (3) to determine whether the effective stability of the spine could be predicted by the active spine stability and belt condition. Electromyographic (EMG) and trunk stiffness data from a previously reported experiment in which 10 subjects performed quick-release tasks (pertubation) with and without an abdominal belt were used as inputs to biomechanical models to estimate the active spine stability and effective stability of the spine, respectively. The subjects exerted isometric trunk flexion, extension and lateral bending trials at 0 and 80% of maximum intra-abdominal pressure when the resisted force was suddenly released. Wearing an abdominal belt had no significant effect on either the muscle-generated lumbar spine stability or the L4/L5 joint compression force in any direction. The effective stability of the spine was adequately predicted by the active spine stability and the effect of the belt, which accounted for approximately 34% of the effective spine stability. The study demonstrated that the abdominal belt contributed to the passive stability of the lumbar spine and did not change the active stability for tests performed within the same experimental session.     

The effects of a back belt on posture, strength, and spinal compressive force during static lift exertions

The experiment reported in this paper evaluated changes in lifting posture, static lifting strength and the estimated L3/L4 spinal compressive force resulting from the use of an abdominal support or ‘back' belt. Torso posture and maximum static lift strength were measured for eight male and eight female subjects using symmetric and asymmetric hand positions at calf height and elbow height. Body posture, and hand forces were also used as input to a three-dimensional static biomechanical model of the torso used to estimate L3/L4 spinal compressive force. The results showed axial twist of the torso to be significantly lower for calf height asymmetric exertions when the abdominal support belt was worn. The measured reduction in axial twist was approximately four degrees. No other significant effects on posture due to the support belt were found. Static lift strength was not significantly increased or reduced when the support belt was used. Predicted spinal compressive force was significantly lower when a support belt was worn (2840 N compared to 3125 N when the belt was not worn). Overall, the results of the experiment demonstrate a very limited benefit to the user of abdominal support belts, primarily due to reduced or restricted motion during asymmetric and lower-level lifts.Relevance to industryBack belts are commonly used in industry to mitigate manual materials handling hazards. One assumption often made by those recommending the use of back belts is that they substantially reduce the bending and twisting of the torso. The experiment reported in this paper tests this assumption and provides information on the utility of back belts.     

Effect of load carriage on spinal compression

Backpack is commonly carried either posteriorly or anteriorly. Although load carriage has been shown to have significant effects on postural alignment and spinal muscle activity, its effect on spinal loading was not studied. The objective of this study is to investigate the effect of different load carriage methods on spinal loading over time via the measurement of spinal compression. Eight male adults participated in this study. They were asked to carry a load equivalent to 15% of their body weight either anteriorly or posteriorly for 20 min followed by 10 min of unloading. Their statures were measured before load carriage and every 2 min after carrying the load. The sequence of loading conditions was randomized and the participants took a 20-min rest with Fowler’s posture for spinal length recovery prior to each testing condition. The amount of spinal compression was found to be associated with carrying duration. Spinal compression during anterior carriage was larger than that of posterior carriage. There was a mild recovery of spinal compression after the removal of the carried load for both the anterior and posterior carriage conditions.

Relevance to industry

Short-term putting a backpack anteriorly might be useful for temporarily relieving postural changes induced by posterior carriage. However, prolonged anterior carriage is not recommended. The effects of load carriage on spinal compression should be considered in the design of a load carriage system with load partially or completely positioned in the front     

弹簧压缩屈曲稳定性的数值模拟

为研究弹簧失稳变形时的特性,采用有限元法,考虑到弹簧内部限制失稳构件的刚性和柔性特点对弹簧失稳后弹射力产生的影响,对弹簧限制失稳现象进行数值分析. 结果表明,弹簧弹射力失稳程度较小时,弹射力与理想弹射力相差较小;随着压缩距离的增加,失稳变形程度逐渐增大,弹射力的损失也逐渐增大;由于刚性约束构件比柔性约束构件对弹簧的约束更紧密,所以其弹射力损失较小.     

Design and computational support for the binding stability of a new CCR5/CXCR4 dual tropic inhibitor: Computational design of a CCR5/CXCR4 drug

The human immunodeficiency virus (HIV) infects healthy human cells by binding to the glycoprotein cluster of differentiation 4 receptors on the surface of helper T-cells, along with either of two chemokine receptors, CC chemokine receptor type 5 (CCR5) or C-X-C chemokine receptor type 4 (CXCR4). Recently, a pyrazolo-piperdine ligand was synthesized and the corresponding biological data showed good binding to both chemokine receptors, effectively blocking HIV-1 entry. Here, we exhaustively assess the atomistic binding interactions of this compound with both CCR5 and CXCR4, and we find that binding is driven by π-stacking interactions between aromatic rings on the ligand and receptor residues, as well as electrostatic interactions involving the protonated piperidine nitrogen. However, these favorable binding interactions were partially offset by unfavorable desolvation of active site glutamates and aspartates, prompting our proposal of a new, synthetically-accessible derivative designed to increase the electrostatic interactions without compromising the π-stacking features.     

Comparison of prediction models for the compression force on the lumbosacral disc

The main objective of this research was to compare three representative methods of predicting the compressive forces on the lumbosacral disc: LP-based model, double LP-based model, and EMG-assisted model. Two subjects simulated lifting tasks that are frequently performed in the refractories industry of Korea, in which vertical and lateral distances, and weight of load were varied. To calculate the L5/ SI compressive forces, EMG signals from six trunk muscles were measured, and postural data and locations of load were recorded using the Motion Analysis System. The EMG-assisted model was shown to reflect well all three factors considered here, whereas the compressive forces from the two LP-based models were only significantly affected by weight of load. In addition, low lifting index (LI) values were observed for relatively high L5/S1 compressive forces from the EMG-assisted model, suggesting that the 1991 NIOSH lifting equations may not fully evaluate the risk of dynamic asymmetric lifting tasks.     

On the stability of plates under combined compression and in-plane bending

The conventional stability analysis of plates under combined compression and in-plane bending is based on the assumption that the plate is free to move laterally and, hence, the restraints imposed by the attached elements against this motion are ignored. The paper explores the influence of these restraints on the plate under this type of loading. The unloaded edges are assumed to be partially restrained against in-plane translation while remaining straight and the distributions of the resulting forces acting on the plate are shown. The stability analysis is done numerically using the Galerkin method and various strategies that economize the numerical implementation are presented. The results are obtained showing the variation of the buckling load, from free edge translation to fully restrained, for simply supported and clamped unloaded edges for various plate aspect ratios and stress gradient coefficients. An apparent decrease in the buckling load is observed due to these destabilizing forces acting in the plate and changes in the buckling mode are observed by increasing the intensity of the lateral restraint. A comparison is made between the buckling loads predicted from various formulae in stability standards based on free edge translation and the values derived from the present investigation. A difference of about 34% in the predicted buckling load and different buckling load were found.     

Reassessment of the role of intra-abdominal pressure in spinal compression

Biomechanical models used to estimate loads on the lumbar spine often predict internal low back forces for heavy lifts that exceed known tissue tolerances, yet the particular lift caused no apparent damage to the lifter. To deal with this paradox, many researchers have incorporated some form of spinal compression alleviation from intra-abdominal pressure (IAP). The purpose of this work was to re-examine some of the issues involved in the feasibility of IAP to reduce spinal loads during stressful lifts. Questions remain over the trade-off between the beneficial tensile force on the spine, exerted via the diaphragm and pelvic floor when IAP is produced, and the undesirable compressive effects of abdominal muscular force required to maintain the pressure within the abdomen. Various strategies of modelling IAP and its effects on low back loading were employed, Three major differences between this and most previous models of IAP effects were the attempt to quantify the size of abdominal muscle forces and the utilization of a considerably smaller diaphragm cross-sectional area and corresponding IAP moment arm. Abdominal EMG recorded from rectus abdominis, external oblique and internal oblique generally indicated low levels of activity throughout the high loading phase of the lifts. However, model output predicted that the compressive forces generated by the abdominal wall musculature were larger than the beneficial action of those forces thought to alleviate spinal compression via IAP. These results suggest that modelling IAP as a force vector which produces a trunk extensor moment and lumbar disc compression alleviation, without accounting for the compressive effects of abdominal muscle forces required to produce the IAP, is incorrect. This does not exclude a possible role of IAP in assisting the trunk during loading, only that the role of IAP is not modelled properly at present. IAP may indeed play a role in spinal stabilization as yet not well understood.     

Study on effects of spinal joint for running quadruped robots

Intelligent Service Robotics - Most legged animals use their flexible body and supporting muscles to produce power for their locomotion, resulting in superior mobility and fast motions. In reality,...     

Two linear regression models predicting cumulative dynamic L5/S1 joint moment during a range of lifting tasks based on static postures

Previous studies have indicated that cumulative L5/S1 joint load is a potential risk factor for low back pain. The assessment of cumulative L5/S1 joint load during a field study is challenging due to the difficulty of continuously monitoring the dynamic joint load. This study proposes two regression models predicting cumulative dynamic L5/S1 joint moment based on the static L5/S1 joint moment of a lifting task at lift-off and set-down and the lift duration. Twelve men performed lifting tasks at varying lifting ranges and asymmetric angles in a laboratory environment. The cumulative L5/S1 joint moment was calculated from continuous dynamic L5/S1 moments as the reference for comparison. The static L5/S1 joint moments at lift-off and set-down were measured for the two regression models. The prediction error of the cumulative L5/S1 joint moment was 21±14 Nm × s (12% of the measured cumulative L5/S1 joint moment) and 14±9 Nm × s (8%) for the first and the second models, respectively.

Practitioner Summary: The proposed regression models may provide a practical approach for predicting the cumulative dynamic L5/S1 joint loading of a lifting task for field studies since it requires only the lifting duration and the static moments at the lift-off and/or set-down instants of the lift.     

基于4L20D 大数据的5G 精准规划方法研究

With the large-scale construction of the 5G mobile communication and rapid increase of 5G users, the problems faced by5G network planning and construction are becoming more and more prominent. Traditional wireless network planning mainly relieson manual selection, which leads to coverage target deviation and waste of investment. A big data scoring system is proposed basedon geographic data, network operation data, resource situation, business forecasting, which contains four levels and twenty dimen-sions. Focusing on network problems and valuable users through big data scoring, accurate 5G network planning is realized.     

支吊架用卷边槽钢压弯构件的整体稳定性计算

为研究支吊架用卷边槽钢压弯构件的稳定性,采用有限元法进行屈曲模态仿真试验,分析截面尺寸、偏心距、长细比等因素对构件屈曲模态的影响,并与《冷弯薄壁型钢结构技术规范》(GB 50018-2002)中稳定性计算公式的结果进行对比,结果表明:随着腹板高度和板厚的增大,稳定承载力增大;随着偏心距和长细比的增大,稳定承载力降低;构...     

ANSYS在平板式压电四维力/力矩传感器设计中的应用

针对人机触觉交互系统对四维力/力矩传感器的需求,研制了一种新型平板式压电四维力/力矩传感器。首先,介绍了传感器的结构和工作原理。然后,推导了传感器的数学模型,建立了传感器的有限元模型。最后,得到了传感器输出的电荷灵敏度、维间干扰、固有频率等重要性能指标。研究结果表明:传感器结构简单合理、数学模型正确、加工工艺性好、线性度好、刚度高、固有频率大于30kHz、未使用退耦矩阵时的维间干扰小于3%。满足传感器的设计指标。     

Effects of combined wrist flexion/extension and forearm rotation and two levels of relative force on discomfort

This study investigated perceived discomfort in an isometric wrist flexion task. Independent variables were wrist flexion/extension (55%, 35% flexion, neutral, 35% and 55% extension ranges of motion (ROM)), forearm rotation (60%, 30% prone, neutral, 30% and 60% supine ROM) and two levels of flexion force (10% and 20% maximum voluntary contraction (MVC)). Discomfort was significantly affected by flexion force, forearm rotation and a two-way interaction of force with forearm rotation (each p < 0.05). High force for 60%ROM forearm pronation and supination resulted in increasingly higher discomfort for these combinations. Flexion forces were set relative to the MVC in each wrist posture and this appears to be important in explaining a lack of significant effect (p = 0.34) for flexion/extension on discomfort. Regression equations predicting discomfort were developed and used to generate iso-discomfort contours, which indicate regions where the risk of injury should be low and others where it is likely to be high. Regression equations predicting discomfort and iso-discomfort contours are presented, which indicate combinations of upper limb postures for which discomfort is predicted to be low, and others where it is likely to be high. These are helpful in the study of limits for risk factors associated with upper limb musculoskeletal injury in industry.     

Hybrid active/passive force control strategy for grinding marks suppression and profile accuracy enhancement in robotic belt grinding of turbine blade

Grinding marks and traces, as well as the over- and under-cutting phenomenon are the severe challenges in robotic abrasive belt grinding of turbine blades and it greatly limits the further application of robotic machining technology in the thin-walled blade fields. In the paper, an active force control method consisting of force/positon and PI/PD controller based on six-dimensional force/torque sensor is introduced to eliminate the grinding marks and traces, and a passive force control method including PID controller based on one-dimensional force sensor is proposed to reduce the over- and under-cutting phenomenon in robotic machining system. Then the Kalman filter information fusion methodology is adopted to combine the active and passive force control methods which could improve the controlled force accuracy and efficiency, as well as avoid the control interference. Finally both the test workpiece and turbine blade are employed to examine and verify the reliability and practicality of the proposed hybrid force control method by achieving the desired surface quality and higher profile precision.