Lumbar Load Research Articles

Evaluation of the effect of lumbar posture and load magnitude on trunk muscles activities

Evaluation of the effect of lumbar posture and load magnitude on trunk muscles activities

水泳運動における腰椎の負荷と挙動のシミュレーションと実験的検証

水泳運動における腰椎の負荷と挙動のシミュレーションと実験的検証

Limiting performance analysis of biomechanical systems for optimal injury control – Part 2: Applications

Applications of the limiting performance analysis of biomechanical systems for optimal injury control are presented. A brief review of applications based on lumped-parameter injury models is given, which includes the problems of helmets with head injuries, seat belts with thoracic injuries, helicopter seat cushions with spinal injuries, toepan padding with lower limb injuries, and child seat sled test corridors with best and worst responses. Then, the problem of ejection seat cushions for the optimal control of spinal injuries is investigated. A rigid multi-body model is developed to describe the biodynamics of the entire system including the occupant. Peak lumbar load in the vertical direction is used as the safety performance index for ejection seat cushions and is minimized. Parametric optimization is performed on a particular cushion to find its optimal performance.

Static Load Repetition Is a Risk Factor in the Development of Lumbar Cumulative Musculoskeletal Disorder

In vivo feline model subjected to variable number of repetitions of a short static lumbar flexion followed by an equally long rest period. The purpose of this study was to determine the influence of the number of repetitions as a risk factor in promoting a cumulative low back disorder in the feline model. Epidemiologic data point out that the increased number of repetitions of static lumbar loading is a major risk factor in the development of cumulative low back disorder. Biomechanical and physiologic confirmation of the epidemiology is lacking. Recent work demonstrated that repetitive static loading results in accumulation of creep in the lumbar viscoelastic tissues, resulting in a neuromuscular disorder consisting of spasms during loading and hyperexcitability of lumbar muscles during following rest. It was also shown that the load magnitude is a major risk factor. It is hypothesized that increased number of repetitions of static load periods result in increased severity of the resulting neuromuscular disorder. Static lumbar flexion of 10 minutes duration followed by 10 minutes rest was repeated three times in one experimental group, six times in the second, and nine times in the third group. In all groups, the creep developing in the lumbar viscoelastic tissues as well as the reflexive EMG from the multifidus were monitored during the flexion/rest periods and throughout a 7-hour recovery period after the repetitions. Creep developed and accumulated during each of the flexion/rest periods in the three experimental protocols, with larger residual creep at the end of the nine repetitions. A residual creep was still present at the end of the 7 hours of recovery allowed in each of the three groups. During the flexion/rest sessions, EMG spasms were present, and the presence of an initial hyperexcitability was detected during the 7 hours of recovery in all the preparations. The presence of a delayed hyperexcitability was revealed only in the group subjected to nine flexion/rest periods, while it was not observed in the groups subjected to three and six flexion/rest repetitions. The statistical analysis (post hoc Fisher test) performed on the normalized integrated EMG and displacement data during the recovery phase showed a significant difference between the nine repetitions group and the other two groups (P < 0.0001). The two-way ANOVA analysis revealed a significant effect of time (P < 0.005) and number of repetitions (P < 0.0001) on all considered parameters. It was concluded that a cumulative neuromuscular disorder develops because of repetition of static lumbar flexion, and the severity of the disorder provoked is magnified by the number of repetitions. Despite the highly favorable 1:1 work-to-rest ratio and the 7-hour post loading rest period, a full recovery of creep was not obtained in this study.

Frequency-dependent changes in neuromuscular responses to cyclic lumbar flexion

Repetitive lifting in the workplace has been identified to be a cause of low back disorders. Epidemiologic data further supports an hypothesis that higher repetition rate (i.e. frequency) is an added risk factor. The objective of this study was to provide experimental data testing the above hypothesis. An in vivo feline model was subjected to 20-min of cyclic lumbar loading at frequencies of 0.1 Hz and 0.5 Hz while monitoring the EMG from the L-3/4–L-5/6 multifidus muscles and the creep at the L-4/5 level. Seven hours of rest were allowed after the cyclic flexion/extension was terminated. During this rest period, a single test cycle was performed every hour to assess recovery of EMG and lumbar creep. The results demonstrate that cyclic lumbar flexion elicits a transient neuromuscular disorder consisting of EMG spasms during the cyclic loading and initial and delayed muscular hyperexcitabilities during the rest period. Cyclic loading at 0.5 Hz resulted in significant ( p<0.05) increase in the hyperexcitability magnitude and duration during the recovery period. It was concluded that repetitive lumbar loading at fast rates is indeed a risk factor as it induces larger creep in the lumbar viscoelastic tissues which in turn intensify the resulting neuromuscular disorder.

707 水泳運動における腰椎の負荷と挙動のシミュレーション(人体のモデル化,ヒューマン・ダイナミクス(1))

707 水泳運動における腰椎の負荷と挙動のシミュレーション(人体のモデル化,ヒューマン・ダイナミクス(1))

Finite element analysis of impacts on water and its application to helicopter water landing and occupant safety

The study of hydrodynamic impact between a body in motion and a free water surface finds applications, in aeronautical fields, in splashdown and ditching problems. The effect of this impact is often prominent in the design phase of the project and, therefore, the importance of studying the event with more accuracy than in the past is imperative. Usually the study of the phenomenon is dealt with experiments, empirical laws, and lately, with finite element simulations. These simulations are performed by means of special codes that allow the fluid-structure coupling; these codes have their origin in Lagrangian finite element programs developed for crash analysis improved with possibility of interfacing with Eulerian spatial description, typical of fluids. Critical points in this type of modelling are the fluid-structure interaction algorithms, constitutive modelling of the fluid and time efficiency of the computation. This study describes an effort that focuses on the development of a crash modelling and simulation approach utilizing a non-linear explicit finite-element code (LSDYNA 960) to demonstrate the potential for helicopter water impact analysis in the development of crash design criteria and concepts. Initially, the water model shall be developed and validated using default Lagrangian techniques. Subsequently, more accurate Arbitrary Lagrangian Eulerian analyses will be conducted to obtain finer results for the ball impact scenario and helicopter impact. Finally, the response of an occupant for the above helicopter crash test shall be analyzed using the MADYMO code, utilizing accelerations obtained from the LSDYNA output. Lumbar load, the most crucial mode of injury in these types of crashes will be investigated and discussed.

Lumbar loading during lifting: a comparative study of three measurement techniques

Low back loading during occupational lifting is thought to be an important causative factor in the development of low back pain. In order to regulate spinal loading in the workplace, it is necessary to measure it accurately. Various methods have been developed to do this, but each has its own limitations, and none can be considered a “gold standard”. The purpose of the current study was to compare the results of three contrasting techniques in order to gain insight into possible sources of error to which each is susceptible. The three techniques were a linked segment model (LSM), an electromyographic (EMG)-based model, and a neural network (NN) that used both EMG and inertial sensing techniques. All three techniques were applied simultaneously to calculate spinal loading when eight volunteers performed a total of eight lifts in a laboratory setting. Averaged results showed that, in comparison with the LSM, the EMG technique calculated a 25.5±33.4% higher peak torque and the NN technique a 17.3±10.5% lower peak torque. Differences between the techniques varied with lifting speed and method of lifting, and could be attributed to differences in anthropometric assumptions, antagonistic muscle activity, damping of transient force peaks by body tissues, and, specific to the NN, underestimation of trunk flexion. The results of the current study urge to reconsider the validity of other models by independent comparisons.

Practice-related changes in lumbar loading during rapid voluntary pulls made while standing

Objective. To determine if five days of practice on a novel dynamic, multi-joint pulling task resulted in lower magnitudes of lumbar loading or a more consistent relationship between pulling force and lumbar loading. Design. A repeated measures design compared how practice influenced the magnitude of lumbar torque and the correlations between lumbar torque and pulling force. Background. Previous studies suggest that practice can decrease the magnitude of lumbar loading on simple manual material handling tasks, but it is unknown whether practice reduces lumbar loading for more complex tasks. Neither is it known whether the consistency of lumbar loading increases with practice. Methods. Ten healthy adults practiced impulse-like horizontal pulls to targets equaling 20%, 40% and 80% of their estimated maximal dynamic pulling force over 5 days. Movements were unrestrained, other than keeping the feet flat on the ground. We used a four-segment, sagittal plane inverse dynamics model to compute lumbar, hip, knee, and ankle torques on days 1 and 5 from ground reaction forces and moments, pulling forces, and kinematics. Results. An analysis of variance showed significant practice-related changes in lumbar torque at the time of peak pulling force (lumbar torque peakPF). The lumbar torque peakPF decreased for the 20% pulls, did not change for the 40% pulls, and increased for the 80% pulls. Two subjects showed a significant decrease in lumbar torque peakPF for all three force levels. Coefficients of determination between pulling force and lumbar torque ( r 2 PF,LT: a measure of the consistency of the relationship between these two variables) were significantly higher on day 5 than day 1. Conclusions. Practice on a novel pulling task changed the magnitude of lumbar torques and increased their correlation with pulling force, suggesting that subjects learned strategies that improve motor control of lumbar torques. Relevance The study showed that the magnitude and consistency of lumbar loading changed spontaneously as subjects practiced a novel multijoint pulling task. Such changes may decrease the risk of low-back injury.

Biomechanical Analysis of Low - Back Load during Materials Handling and its Whole - Shift Monitoring within the Dortmund Lumbar Load Study - Dolly

In the so-called Dortmund Lumbar Load Study (DOLLY), the load on the lumbar spine was quantitatively monitored for complete shifts in diverse fields, i.e. for the materials handling tasks in construction and metal-processing industries as well as in a meat-processing factory and for dustbin removal. Video recording of 8 shifts was performed, actual posture was described and the action forces applied at the hands were determined for each work situation. Based on the respective data for posture and handforces, lumbar load was calculated applying the 3D biomechanical model The Dortmunder for each working situation, in total between approx. 4 and 22 thousands per shift. Shift-monitored temporal profiles for several load indicators - trunk flexion and torsional moments, compression and shear forces with respect to the lumbosacral joint - describe the load on the lumbar spine. Comprehensive results with regard to posture, handforces and lumbar load are available. Several load indices regarding load level, duration and the cumulative effects were defined and applied for assessing the analysed jobs. In relation to recommended limits for the maximal disc compression, lumbar load is exceeded in numerous situations during a shift, in particular, with regard to persons of higher age. In a “dose model” developed in this study, the cumulative effect of single-task exposures was considered by superproportional weighting of the compressive force with respect to the corresponding duration of a working task, based on the higher injury potential of high loads compared to - although longer effective - low loads.

Trunk Modelling Procedures and Errors in Net Lumbar Loading

The use of 3D upper body link models to estimate net lumbar loading requires adequate modelling of the trunk segment. Various methods to obtain body segment parameters and partition the trunk were contrasted to evaluate their impact on L5/S1 net joint moments for some simple and complex lifting tasks. Appropriate combinations of body segment parameters and trunk partitioning reduced L5/S1 net joint moment errors, especially for subjects characterised by a larger abdomen. Trunk modelling procedures considering the variability inherent to trunk morphology and non-rigidity should be preferred for inverse dynamic analysis of lifting through an upper body link model.

Evaluation and assessment of lumbar load during total shifts for occupational manual materials handling jobs within the Dortmund Lumbar Load Study – DOLLY

The load on the lumbar spine during occupational manual materials handling was previously investigated with respect to short activity sections or to specified load-handling types such as lifting or carrying. Within the so-called Dortmund Lumbar Load Study, analysis of the occupationally induced load on the lumbar spine during total working shifts in the field of surface construction, drop forge, industrial meat processing, and refuse collection was performed on the shop-floor. The body postures adopted, the action forces applied at the hands, and the resultant lumbar load for all load-handling tasks were analysed for 2 shifts in each field on the basis of video evaluations. Via a newly developed detailed classification procedure, the spatial position of the body segments as well as amplitude and direction of the action forces were described in a detailed manner. Consecutive biomechanical model calculations lead, for total shifts, to time courses of various measures for the load on the lumbar spine, such as flexion or torsional moments of force as well as compression and shear forces at the lumbosacral disc. In relation to recommended limits for the maximal disc compression provided in the literature, lumbar load is exceeded in numerous situations during a shift, in particular, with regard to persons of higher age. In a “dose model” applied in this study, the cumulative effect of single-task exposures was considered by superproportional weighting of the compressive force with respect to the corresponding duration of a working task. Relevance to industry A comprehensive evaluation of lumbar load for complete shifts is presented considering the real shop-floor conditions. Analyses for dustbin removal, surface construction and industrial meat processing have discovered numerous exceedings of lumbar-load limits. Such tasks should not be performed by older persons from the preventive point of view.

Validation of a questionnaire for assessing physical work load.

Reliable, valid, and compatible methods are required for exploring the complex interactive effects of psychosocial and physical stressors on complaints and disorders. An instrument for assessing physical work load that integrates information from a biomechanical model of lumbar load is presented and validated. Four hundred and fifty-five people working in nursing homes for elderly people in Germany filled out the developed questionnaire 3 times within 1 year. Test-retest reliability was calculated, and validity was checked several times. Relationships with other, theoretically related and unrelated variables were examined. The test-retest reliability of the questionnaire measures was about 0.65. The convergent and discriminant validity was satisfactory, and the questionnaire was able to separate professional subgroups with different physical work loads. The Spearman rank-order correlations between physical load and musculoskeletal complaints were about 0.30. The method developed in this study is a reliable and valid instrument for assessing physical work load. The integration of statistical methods from psychological testing and theory in the development of methods exploring the effects of physical work load is advocated.

移乗介助動作における腰部負担の計測と評価

移乗介助動作における腰部負担の計測と評価

Biomechanical estimation of lumbar load on transferring assistance

Biomechanical estimation of lumbar load on transferring assistance

Critical survey on the biomechanical criterion in the NIOSH method for the design and evaluation of manual lifting tasks

In 1981, the National Institute for Occupational Safety and Health (NIOSH) published a comprehensive guide for the evaluation and design of manual lifting, based on epidemiological, physiological, psychophysical, and biomechanical knowledge. A revised version of the easy-to-use “NIOSH lifting equation” was provided in 1991 considering occasional new findings from literature. For assessing the load on the lumbar spine during lifting, a limit of 3.4 kN for lumbosacral disc compression was introduced. Regarding this biomechanical criterion, several inconsistancies and discrepancies are revealed when comparing the NIOSH substantiation approaches and the respective data of the literature sources: For example, essential results referred to by NIOSH or NIOSH-authorized presenters are not included in or cannot be reproduced from the cited sources. Furthermore, the epidemiological studies showing the relationships between low-back disorder incidence rates and lumbar mechanical exposures cannot be used for confirming the 3.4 kN value as an appropriate limit. It is concluded that the 3.4 kN criterion is substantiated neither epidemiologically nor biomechanically by the provided sources. More comprehensive data compilations, available in the meantime, may be regarded as a better background for the derivation of lumbar load limits in order to diminish the individual overexertion risk during manual materials handling. Relevance to industry NIOSH has provided a multi-disciplinarily justified lifting guide for evaluation and design of lifting tasks. A critical survey of the cited sources shows that the considered biomechanical criterion is only weakly substantiated.

A model of spine, ribcage and pelvic responses to a specific lumbar manipulative force in relaxed subjects

One class of manipulative techniques commonly used during assessment and treatment of spinal disorders involves the patient lying face down while the therapist slowly applies a posteroanterior force to a selected vertebra. The aim of this investigation was to develop a model which was capable of predicting the vertebral displacements resulting from such a manipulative force, applied to the lumbar spine. A linear three-dimensional finite element model was generated using both previously published and original data to define the geometry and material properties. The complete model included the ribcage, thoraco-lumbar spine and pelvis with their associated soft tissues. The model simulated the relaxed state in a normal subject so the muscle forces were assumed to be negligible. Sensitivity analysis suggested that if the model was to be used to simulate the behaviour of individual subjects, then the model dimensions and pelvic constraints should be matched to the particular subject. The model validity was studied by comparing the predicted responses with those that have been observed in living human subjects. The model predictions were found to be in good agreement with the mean observed human responses, with predicted displacements being within one standard deviation of the mean observed values. This agreement suggests that the model is useful for predicting the linear region responses to slowly applied lumbar posteroanterior forces. The simulations predicted that appreciable global vertebral displacements (up to 1.5 mm) and rotations (up to 1°) occurred as far away as the middle and lower thoracic spine during low lumbar loading. Intervertebral translations were predicted to be 1 mm or more at up to four intervertebral jonts away from the point of load application. Variation of direction of applied force was predicted to have small effects on displacement responses compared with loading at different lumbar levels.

Transfer of lumbosacral load to iliac bones and legs: Part 2: Loading of the sacroiliac joints when lifting in a stooped posture

We developed a biomechanical model of load transfer by the sacroiliac joints in relation to posture. A description is given of two ways in which the transfer of lumbar load to the pelvis in a stooped posture can take place. One way concerns ligament and muscle forces that act on the sacrum, raising the tendency of the sacrum to flex in relation to the hip bones. The other refers to ligament and muscle forces acting on the iliac crests, raising the tendency of the sacrum to shift in caudal direction in relation to the hip bones. Both loading modes deal with the self-bracing mechanism that comes into action to prevent shear in the sacroiliac joints. When a person is lifting a load while in a stooped posture, the force raised by gravity acting in a plane perpendicular to the spine and the sacrum becomes of interest. In this situation a belt such as used by weight lifters may contribute to the stability of the sacroiliac joints. Verification of the biomechanical model is based on anatomical studies and on load application to human specimens. Magnetic resonance imaging pictures have been taken to verify geometry in vivo.

The load on the lumbar spine during asymmetrical bi-manual materials handling.

Previous biomechanical analyses of typical load manipulation tasks were mainly limited to sagittal-plane activities or to static cases. This paper includes the biomechanical determination and assessment of lumbar load during asymmetrical bi-manual materials handling tasks which involve lateral turning of the body, trunk inclination, and sagittal flexion and lateral bending of the spine. Diagonal lifting tasks were analysed for different values for load weight (0-40 kg) and task duration (0.75-1.5 s). Whereas a constant grasp height of 15 cm was assumed, the height for releasing the load differed (50, 100, 150 cm). A dynamic spatial human model ('The Dortmunder') was used for calculating the torque in the sagittal, frontal, and transversal planes through the lumbosacral joint and for determining the compressive and the sagittal and lateral shear force at the L5-S1 disc. The trajectories of body segments and load are computer-simulated on the basis of postures adopted during the movement. During diagonal lifting of loads, lumbosacral torque in the sagittal plane is considerably larger than the lateral bending and torsional torque components. Dynamic analyses result in higher maximum values in the lumbar-load time curves than static analyses. The shorter the time for task execution, the higher the resultant dynamic effects and, in consequence, the higher the lumbar load. Lumbosacral compression and shear increase with increasing load-release heights due to higher acceleration and retardation of body and load when the same grasp position and task duration are assumed. The maximum load-bearing capacity of the lumbar spine was determined on the basis of strength data for isolated lumbar segments provided in the literature. The compressive strength falls within the same range as the compressive forces calculated for asymmetrical lifting of loads up to 40 kg. On account of the wide scattering of the compressive strength values, the main influences were determined (age and gender). At an age of 40 years, strength is approx. 6.7 kN for males and 4.7 kN for females (decrease with age per decade: 1.0 kN males, 0.6 kN females). In order to avoid overestimating an individual's lumbar compressive strength, predicted values should be reduced, e.g., by the standard deviation in the male or female samples (2.6 kN or 1.5 kN). Although only a few maximum shear force values are available in the literature, comparison with the calculated values for diagonal lifting leads to the conclusion that sagittal and lateral shear should not be ignored in the assessment of lumbar load during asymmetrical handling tasks.

Lumbar load during one-handed bricklaying

Lumbar load, as indicated by the moment of force and the force at the lumbosacral disc, was determined for one-handed bricklaying tasks using a dynamic 3-D model, ‘The Dortmunder’. The grasp height differed (90, 50, 10 cm). By contrast, the final postures were assumed almost upright in all cases. This resulted in considerable variance in the postures during the computer-simulated movements. The task duration varied (2.0, 1.5, 1.0 s). The lower the grasp height and the shorter the time, the higher the lumbar load (moment of force at L5-S1 up to 140 Nm, compressive force up to 6 kN), and the larger the differences between dynamic and static calculations. Increasing brick mass (0, 5, 10 kg) leads to an upward shift in the moment and compression curves (20 Nm or 1 kN per 5 kg). For the assessment of lumbar load during the analysed bricklaying tasks, the lumbosacral moment of force was first classified accoding to Tichauer (1978). Bricklaying involving a 50 cm grasp height requires ‘selection of labor, careful training and rest pauses’. Lower grasp heights of bricks of 10 kg should not occur throughout ‘the entire working day’. Lumbosacral force was then compared with lumbar strength values provided in the literature. These vary within a wide range (0.8–13 kN). Strength mean ± s. d. amounts to 5.0 ± 2.2 kN for the total sample ( n = 507), to 5.8 ± 2.6 kN for males ( n = 174) and to 4.0 ± 1.5 kN for females ( n = 132). Strength dependes primarily on age. Assuming linear regression models, strength (in kN) is 10.53-0.97/decade for males ( r 2 = 0.39) and 7.03-0.59/decade for females ( r 2 = 0.35). A strength prediction model considering 3 additional factors was developed ( r 2 = 0.62) in order to explain most of the remaining variance. Since average values may overestimate an individual's strength, the mean or regression model value should be reduced by the s. d. of the respective sample. This would result in a lumbar load limit of 5.5 kN for 25-year-old men and 2.6 kN for 55-year-old men. Corresponding values for women are 4.1 and 2.3 kN. If the brick-supply stack is 90 cm high, the lumbar load limits will not be exceeded for any person in these age groups. By contrast, all limits would be exceeded for a 10-kg 1-s brick transfer from a grasp height of 10 cm. In conclusion, to ensure that the predicted lumbar load during bricklaying remains below the limits, the brick-supply stack should be above 50 cm.