Influence of the mode of load carriage on the static posture of the pelvic girdle and the thoracic and lumbar spine in vivo (original) (raw)
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The effect of sitting posture on the loads at cervico-thoracic and lumbosacral joints
Technology and Health Care
BACKGROUND: The sitting in an awkward posture for a prolonged time may lead to spinal or musculoskeletal disease. It is important to investigate the joint loads at spine while sitting. OBJECTIVE: The purpose of this study was to investigate the joint moment and antero-posterior (AP) reaction force at cervico-thoracic and lumbosacral joint for various sitting postures. METHODS: Twenty healthy males participated in this study. Six sitting postures were defined from three spinal curvatures (slump, flat, and lordosis) and two arm postures (arms-on-chest and arms-forward). Kinematic and kinetic data were measured in six sitting postures from which joint moment and AP reaction force were calculated by inverse dynamics. RESULTS: In the cervico-thoracic joint, joint moment and AP reaction force were greater in slump than the flat and lordosis postures (p < 0.001) and also in arms-forward posture compared to arms-on-chest posture. In the lumbosacral joint, joint moment and AP reaction force were greater in slump than flat and lordotic posture (p < 0.001) but there was no difference between different arm postures. The joint loads (moment and AP reaction force) at the cervico-thoriacic joint were closely related to the head flexion angle (r > 0.86) while those at the lumbosacral joint were correlated to the trunk flexion angle (r > 0.77). In slump posture, the joint moments were close to or over the extreme of the daily life such as sit-to-stand and walking. Consequently, if the slump is continued for a long time, it may cause pain and diseases at the cervico-thoracic and lumbosacral joints. CONCLUSIONS: The results of the study indicated that the lordosis or flat would be better spinal postures. Also, keeping arms close to body would be desirable to reduce joint loads.
Ergonomics, 2001
Loading of the spine is still not well understood. The most reliable results seemed to come from the intradiscal pressure measurements from studies by . A new similar study by complemented the present study and con® rmed some of the earlier data, although it contradicted others. The new data did not con® rm that the load on the spine is higher in sitting compared with standing and did not ® nd distinct diOE erences between positions in which subjects were lying down. The objective of this paper was to compare results from two independent in vivo studies (applying diOE erent methods) to provide information about spinal loading. In one of these studies (Wilke 1999), intradiscal pressure was measured in one volunteer in diOE erent postures and exercises, and in the other study ) the loads on an internal spinal ® xation device (an implant for stabilising unstable spines) were determined in 10 patients. The absolute values of the results from both studies were normalized and compared for many body positions and dynamic exercises. The relative diOE erences in intradiscal pressure and¯exion bending moments in the ® xators corresponded in most cases. Both studies showed slightly lower loads for sitting than for standing and comparatively low loads in all lying positions. High loads were measured for jogging, jumping on a trampoline and skipping. DiOE erences between trends for intradiscal pressure and for¯exion bending moments in the ® xators were found when the load was predominantly carried by the anterior spinal column, as durinḡ exion of the upper part of the body or when lifting and carrying weights. The combination of the results from these two methods may improve the understanding of the biomechanical behaviour of the lumbar spine and may be used to validate models and theories of spinal loading.
Lumbar-load analysis of a soldier while carrying the heavy loads
Periodicals of Engineering and Natural Sciences, 2019
Background: The aim of the article was to create an appropriate computer model based on the real status of the mortar operator's workplace and to analyze the workplace. After that, for any possible exceedances from the aspect of the organism's load and safety, the aim is to redesign the workplace and bring it within the limits of the permissible load, and therefore the required safety. The aim is also to identify the characteristic work movements performed by the soldier and to carry out an ergonomic analysis of the soldier's efforts and to propose appropriate improvements. Methods: The analysis is performed on a total of 20 soldiers, from which is determined an average model of the following characteristics: 180 cm in height and 85 kg in weight. The task is to take a mine from the shell containing the mines, then transfer it to the mortar and fill the mortar barrel. The weight of the 120 mm mortar grenade is 14.8 kg. The average soldier is 26 years old and his military exercise lasts 4 hours. The CATIA software package (Dassault Systèmes, Vélizy-Villacoublay, France) is used for analysis. By knowing the anthropometric and work environment data, with ergonomic design and analysis, the following analyses were made: biomechanical analysis, rapid upper limb assessment (RULA) and carry analysis (option from CATIA software). Results: The proposed modification of the position resulted in a decrease in the L4/L5 torque from 316 Nm to 154 Nm along with decreasing of the compression force on the L4/ L5 from 5,779 N to 3038 N (the compression force allowed is 3,400 N), and while the RULA analysis is from the red color position 1 (score 7; maximum load requiring rapid repositioning of such position), revised final score 4 made in yellow (a solution acceptable for this work place). Conclusions: By ergonomic analysis, obtained proposal will lead to less chance of injury, prevention of burn out syndrome, fewer chances of illness, decreasing the fatigue, greater safety, less energy spent and better preparedness for all necessary tasks.
Lumbar spinal loads vary with body height and weight
Medical Engineering & Physics, 2013
Knowledge about spinal loading is required for designing and preclinical testing of spinal implants. It is assumed that loading of the spine depends upon body weight and height, as well as on the spine level, but a direct measurement of the loading conditions throughout the spine is not yet possible. Here, computer models can allow an estimation of the forces and moments acting in the spine. The objective of the present study was to calculate spinal loads for different postures and activities at several levels of the thoracolumbar spine for various combinations of body height and weight.
Effect of load carriage on spinal compression
International Journal of Industrial Ergonomics, 2011
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 Ó
Evaluation of spinal loading during lowering and lifting
Clinical Biomechanics, 1998
Objective. To estimate the three-dimensional spinal loads during various lifting and lowering tasks. Design. The in viva measurements of the trunk dynamics, moments, and myoelectric activity were used as inputs into an electromyographic-assisted model used to predict the three-dimensional spinal loads. Background. Previous studies of eccentric motions have investigated muscle activity, trunk strength, and trunk moments. A void in the body of knowledge exists in that none of these studies investigated spinal loading. Methods. Ten subjects lifted (40" of flexion to 00) and lowered (0" of flexion to 40") boxes while positioned in a structure that restrained the pelvis and hips. The tasks were performed under isokinetic trunk velocities of 5, 10, 20, 40, and 80 deg s-l while holding a box with weights of 9.1, 18.2, and 27.3 kg. Results. Lowering strength was found to be 56% greater than lifting strength. The lowering tasks produced significantly higher compression forces but lower anterior-posterior shear Forces than the lifting tasks. The differences in the spinal loads produced by the two lifting tasks were attributed to differences in coactivity and unequal lifting moments (i.e. holding the box farther away from the body). Conclusions. The nature of the spinal loads that occur during lowering and lifting were significantly different. The difference in spinal loads may be explained by different lifting styles. Relevance This study revealed the importance of investigating lowering as well as lifting since these types of motions result in drastically different EMG-torque relationships and, ultimately, different spinal loading patterns. Furthermore, this study indicates the importance of taking into account differences in lifting style (trunk moments) and the coactivity of the trunk muscles when estimating loads on the spine.
Muscle force evaluation and the role of posture in human lumbar spine under compression
European Spine Journal, 2002
Changes in the sagittal curvature of the human lumbar spine (i.e. lordosis) and pelvic orientation have been recorded during various recreational and occupational activities of daily living. Such alterations affect the distribution of gravity and external loads among passive and active sub-systems of the human trunk, thus influencing the stability margin of the system and stress/strain values in comprising tissues. Previous in vivo studies have demonstrated the compensatory changes in the lumbar posture in a variety of conditions: in micro-gravity, under load, in supine position, sitting on chairs with different back inclinations, wearing high-heeled shoes, and in groups of normal and low-back pain populations in standing position . In vivo measurements of normal volunteers, with no instruction on the posture, carrying up to 445 N loads symmetrically in the hands while standing have shown that the pelvis rotates posteriorly and the lumbar spine flattens as the loads increase . There was, however, negligible surface electromyographic (EMG) activity in back superficial muscles, with or without loads in the hands . Although, in general, squat lifting (i.e. knees bent) is considered to be safer than the stoop lifting (i.e. knees straight) in reducing the net moment on the spine, the respective benefits of preserving or changing lordosis during lifting remains less understood.
Stability of the human spine in neutral postures
European Spine Journal, 1997
The present study aimed to identify some of the mechanisms affecting spinal compressive load-bearing capacity in neutral postures. Two spinal geometries were employed in the evaluation of the stabilizing mechanisms of the spine in standing neutral postures. Large-displacement finite-element models were used for parametric studies of the effect of load distribution, initial geometry, and pelvic rotation on the compression stability of the spine. The role of muscles in stabilization of the spine was also investigated using a unique muscle model based on kinematic conditions. The model with a realistic load configuration supported the largest compression load. The compressive load-bearing capacity of the passive thoracolumbar spine was found to be significantly enhanced by pelvic rotation and minimal muscular forces. Pelvic rotation and muscle forces were sensitive to the initial positioning of T1 and the spinal curvatures. To sustain the physiological gravity load, the lordotic angle increased as observed in standing postures. These predictions are in good agreement with in vitro and in vivo observations. The load-bearing potential of the ligamentous spine in compression is substantially increased by controlling its deformation modes through minimal exertion of selected muscles and rotation of the pelvis.
The effect of axial load on the sagittal plane curvature of the upright human spine in vivo
Journal of Biomechanics, 2008
Determining the effect of load carriage on the human spine in vivo is important for determining spinal forces and establishing potential mechanisms of back injury. Previous studies have suggested that the natural curvature of the spine straightens under load, but are based on modelling and external measurements from the surface of the back. In the current study, an upright positional MRI scanner was used to acquire sagittal images of the lumbar and lower thoracic spine of 24 subjects. The subjects were imaged in standing whilst supporting 0, 8 and 16 kg of load which was applied axially across the shoulders using an apron. An active shape model of the vertebral bodies from T10 to S1 was created and used to characterise the effect of load. The results from the shape model showed that the behaviour of the average-shaped spine was to straighten slightly. However, the shape model also showed that the effect of load exhibited systematic variation between individuals. Those who had a smaller than average curvature before loading straightened under load, whereas those who had a greater than average curvature before loading showed an increase in curvature under load. The variation in behaviour of differently shaped spines may have further implications for the effects of load in lifting manoeuvres and in understanding the aetiology of back pain.