Lumbar Load Research Articles

Spino-pelvic-rhythm with forward trunk bending in normal subjects without low back pain.

A strong correlation between low back pain and tight hamstrings has been reported. However, the effect of tight hamstrings on spinal biomechanics remains unclear. The purpose of the study was to investigate spino-pelvic-rhythm during forward bending of the trunk and to clarify the rhythm features with regard to hamstrings tightness. Eighteen healthy male adults with no history of low back pain volunteered to participate. First, we measured the finger-to-floor distance (FFD) in the upright position and set this parameter to 100%. Using a spinal mouse, spinal alignment was measured in the following four positions: (1) upright posture-100% FFD; (2) forward bending-50% FFD; (3) forward bending-25% FFD; and (4) forward bending-0% FFD (fingers in contact with the floor). Changes of the angle of the thoracic and lumbar spine as well as the pelvis were calculated. As an indicator of tight hamstrings, we measured straight leg raising (SLR) angle. From positions 1-2 (phase I), the entire spino-pelvic angle moved in 104°. During this phase, the lumbar spine mainly moved. In the second phase (positions 2-3), it moved in 16°. Interestingly, all but 2 subjects showed a negative angle in the thoracic motion, meaning that the thoracic spine extended 4° during trunk flexion, thus exhibiting paradoxical motion. During this phase, lumbopelvic rhythm showed 2 patterns. In 7 subjects, pelvic motion was greater than lumbar motion, while the remaining subjects showed the opposite. In subjects without tight hamstrings, 83% showed a pelvis-dominant pattern. Only 7 subjects were capable of position 4. During this phase, only slight motion was noted in the spine, and the majority of the motion occurred in the pelvis. Lumbar and pelvic motion correlated negatively in all phases. SLR angle and pelvic motion correlated strongly during phase III, indicating dominant pelvic movement in flexible subjects. The lumbo-pelvic-rhythm comprises 2 patterns-lumbar dominant and pelvis dominant. In flexible subjects, pelvis movement was dominant. In conclusion, improving tight hamstrings may reduce lumbar loading thereby reducing low back pain.

Lumbo-pelvic loading during fast bowling in adolescent cricketers: The influence of bowling speed and technique

This study aimed to assess changes in bowling technique and lumbar load over the course of a bowling spell in adolescent fast bowlers, and to investigate the relationship between lumbar loads during fast bowling and kinematic factors which have previously been associated with low back injury. Three-dimensional motion analysis was carried out on forty participants who performed an 8-over bowling spell. There were no significant changes in bowling technique or lumbar loads over the course of the spell. Bowling with a more extended front knee, faster ball release speed and increased shoulder counter-rotation were related to increased lumbo-pelvic loading – in particular peak transverse plane rotation moments and anterior-posterior shear forces. These lumbar loads may be a factor in low back injury aetiology and future studies should investigate the relationship between lumbar loading, injury incidence and other risk factors.

Lumbar-Load Analysis of Manual Patient-Handling Activities for Biomechanical Overload Prevention Among Healthcare Workers

Manual patient handling commonly induces high mechanical load on the lower back of healthcare workers. A long-term research project, the 'Third Dortmund Lumbar Load Study' (DOLLY 3), was conducted to investigate the lumbar load of caregivers during handling activities that are considered 'definitely endangering' in the context of worker's compensation procedures. Nine types of handling activities in or at a bed or chair were analysed. Measurement of action forces via specifically developed devices and posture recording by means of optoelectronic marker capturing and video recordings in order to quantify several lumbar-load indicators was previously described in detail. This paper provides the results of laboratory examinations and subsequent biomechanical model calculations focused on lumbar load and the potentials of load reduction by applying biomechanically 'optimized' transfer modes instead of a 'conventional' technique and, for a subgroup of tasks, the supplementary usage of small aids such as a sliding mat or a glide board. Lumbosacral-disc compressive force may vary considerably with respect to the performed task, the mode of execution, and individual performance. For any activity type, highest values were found for conventional performance, lower ones for the improved transfer mode, and the lowest compressive-force values were gathered when small aids were applied. Statistical significance was verified for 13 of these 17 comparisons. Analysing indicators for asymmetric loading shows that lateral-bending and torsional moments of force at the lumbosacral disc may reach high values, which can be reduced considerably by implementing an improved handling mode. When evaluating biomechanical loads with respect to age- and gender-specific work-design limits, none of the analysed tasks, despite execution mode, resulted in an acceptable load range. Therefore, applying a biomechanically adequate handling mode combined with small aids to lower the friction between patient and surfaces is highly recommended, especially to prevent overload in older caregivers.

Single-Nucleotide Gene Polymorphisms Involving Cell Death Pathways: A Study of Chinese Patients with Lumbar Disc Herniation

Objective: To evaluate the effect of polymorphisms of death pathway genes FAS and FASL on the risk of developing lumbar disc herniation (LDH) in a Northern Chinese population.Background Data: The FAS receptor–ligand system plays a key role to regulate apoptosis of cell. There is evidence that the apoptosis-mediated FAS receptor–ligand system is involved in the pathogenesis of disc degeneration. Some research considered single-nucleotide polymorphisms of FAS-1377G/A, FAS-670A/G, FASL-844T/C, and FASL INV2nt-124A/G may increase the risk of developing cancer. We therefore assess these four single-nucleotide polymorphisms as candidate susceptibility for LDH.Methods: A total of 475 patients with LDH and 533 control subjects were selected. Genotypes were determined by polymerase chain reaction-based restriction fragment length polymorphism and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Associations with the risk of LDH were estimated by logistic regression model.Results: Significant differences were found in genotypic distributions between cases and controls for FASL-844T/C, but not for other three polymorphisms. When compared with CC genotype, subjects with the TT genotype had a higher risk to develop LDH (odds ratio = 3.12; 95% confidence interval: 1.73–5.40). Moreover, an association was found between this genotype of FASL-844TT and more severe grades of disc degeneration. We observed statistically significant interactions between polymorphisms of FASL-844T/C and lumbar load, tobacco smoking, and age.Conclusion: Genetic polymorphisms of FASL-844T/C may be associated with an increased risk of developing disc degeneration and LDH.

A Controlled Case Study of the Relationship between Environmental Risk Factors and Apoptotic Gene Polymorphism and Lumbar Disc Herniation

To explore the etiologic role of apoptosis-related genes, environmental risk factors, and their interaction in the occurrence of lumbar disk herniation (LDH), a controlled case study was performed with 128 LDH patients and 132 age- and sex-matched controls. Matrix-assisted laser desorption/ionization, time-of-flight mass spectrometry assay was used to analyze the genotype of nine polymorphism sites in three genes, including Fas -1377G/A rs2234767, Fas -670G/A rs1800682, Fas rs2147420, Fas rs2296603, Fas rs7901656, Fas rs1571019, Fas ligand (FasL) -844C/T rs763110, caspase 9 (CASP9) -1263A>G rs4645978, and CASP9 -712C>T rs4645981. The patients and controls showed similar age and sex, but had significant differences in lumbar load, bed type, amateur sports, and leisure activities (P < 0.05). The correlation analysis revealed that polymorphism of FasL -844C/T (rs763110) and CASP9 -1263A>G (rs4645978) had a significant correlation with LDH, indicating that the genotypes of FasL -844C/T TT and CASP9 -1263A>G GG are probably high-risk genotypes for LDH. The results of environment-gene interactionanalysis revealed that, in LDH, the interaction of the FasL -844TT genotype and level III to IV lumbar load was consistent with the ultramultiplying model, and the interaction of the CASP9rs4645978 GG genotype and level III to IV lumbar load was consistent with the submultiplicative model. Therefore, the risk of LDH was determined by both environmental and genetic risk factors, and the mechanisms of interactions between different genotypes and environmental factors also differed.

Lumbar load attenuation for rotorcraft occupants using a design methodology for the seat impact energy-absorbing system

Abstract Aircraft occupant crash-safety considerations require a minimum cushion thickness to limit the relative vertical motion of the seat-pelvis during high vertical impact loadings in crash landings or accidents. In military aircraft and helicopter seat design, due to the potential for high vertical accelerations in crash scenarios, the seat system must be provided with an energy absorber to attenuate the acceleration level sustained by the occupants. Because of the limited stroke available for the seat structure, the design of the energy absorber becomes a trade-off problem between minimizing the stroke and maximizing the energy absorption. The available stroke must be used to prevent bottoming out of the seat as well as to absorb maximum impact energy to protect the occupant. In this study, the energy-absorbing system in a rotorcraft seat design is investigated using a mathematical model of the occupant/seat system. Impact theories between interconnected bodies in multibody mechanical systems are utilized to study the impact between the seat pan and the occupant. Experimental responses of the seat system and the occupant are utilized to validate the results from this study for civil and military helicopters according to FAR 23 and 25 and MIL-S-58095 requirements. A model for the load limiter is proposed to minimize the lumbar load for the occupant by minimizing the relative velocity between the seat pan and the occupant’s pelvis. The modified energy absorber/load limiter is then implemented for the seat structure so that it absorbs the energy of impact in an effective manner and below the tolerable limit for the occupant in a minimum stroke. Results show that for a designed stroke, the level of occupant lumbar spine injury would be significantly attenuated using this modified energy-absorber system.

Biomechanical Trade-Offs in Manual Material Handling: Some Tasks Reduce Lumbar Loading But Increase Thoracic Loading

Job design that is protective of the lumbar spine may inadvertently increase stresses on the thoracic spine, potentially leading to thoracic injury. In this study, we determined the ratio of thoracic to lumbar loading during various tasks, including stoop and squat lifts. Loading on the thoracic spine was calculated based on previously reported thoracic intradiscal pressures and cross-sectional areas, and compared to loading on the lumbar spine calculated using the same methodology. Results demonstrated that the ratio of thoracic and lumbar loading is not uniform and varies with the posture used during manual material handling tasks. Specifically, the loading of the thoracic spine increased during squat lifts, as compared to stoop lifts, whereas the loading on the lumbar spine decreased during squat lifts. This study adds to the body of knowledge that there are trade-offs between squat and stoops lifts and neither are without risks

An investigation into PEEK-on-PEEK as a bearing surface candidate for cervical total disc replacement

Total disc replacement (TDR) is a relatively new reconstructive non-fusion technology for the spine that aims to overcome some of the limitations of fusion technology. The first generation artificial discs were mainly based on well-known material combinations from total hip replacement. To evaluate the feasibility of PEEK-on-PEEK as a bearing surface material for use in cervical TDR. In vitro biotribological study including the assessment of different parameters, including the influence of radial clearance, axial load, and angular motion on the wear performance of a PEEK-on-PEEK bearing. PEEK-on-PEEK bearing couples with ball-and-socket articulation were prepared using standard production methods. Two groups of bearing couples, one with large radial clearances and the other with small radial clearances, were manufactured for testing. Wear tests were performed using a servo-hydraulic wear simulator that allowed controlled motions to be applied in three axes corresponding to flexion-extension, lateral bending, and axial rotation. In addition, a dynamic axial compressive load was applied to simulate the weight of the head. All tests were performed at 37°C (±2°C) in bovine calf serum with a 30 g/l protein concentration. In the first test series, the influence of the radial clearance on the wear behavior was evaluated using the load and motion parameters for cervical TDR as defined in the ISO standard 18192-1. Subsequent tests were performed to check if surface degradation was influenced by thermal effects. Finally, in a third series of tests, the effect of load and motion profiles on wear performance was investigated by applying increased loads and corresponding motion parameters for lumbar TDR as defined in the ISO standard 18192-1. The measured wear rates for a PEEK-on-PEEK bearing under cervical test conditions were considerably larger than those of similar testing using UHMWPE-on-CoCr and seemed to depend on initial radial clearances. The PEEK bearing surfaces exhibited severe surface degradation for large and small clearances, but the group with smaller clearances seemed to have less severe damage. Thermal effects were not found to play a role in the surface degradation, as the temperature near the bearing surface was measured and found to vary only a few degrees during testing. A change of the wear test parameters to simulate lumbar loading resulted in a considerable wear rate reduction as well as in the preservation of the bearing surfaces. It was found that a cervical TDR using a PEEK-on-PEEK bearing may be subjected to severe long-term degradation of the bearing surfaces. In this study, the use of PEEK as an articulation material for cervical TDR was found to be sensitive to loading conditions as well as to the initial clearance of the bearing surfaces. Despite the excellent properties of PEEK as an implant material, its use for articulating surfaces for cervical TDR must be critically reviewed.

Does team lifting increase the variability in peak lumbar compression in ironworkers?

Ironworkers frequently perform heavy lifting tasks in teams of two or four workers. Team lifting could potentially lead to a higher variation in peak lumbar compression forces than lifts performed by one worker, resulting in higher maximal peak lumbar compression forces. This study compared single-worker lifts (25-kg, iron bar) to two-worker lifts (50-kg, two iron bars) and to four-worker lifts (100-kg, iron lattice). Inverse dynamics was used to calculate peak lumbar compression forces. To assess the variability in peak lumbar loading, all three lifting tasks were performed six times. Results showed that the variability in peak lumbar loading was somewhat higher in the team lifts compared to the single-worker lifts. However, despite this increased variability, team lifts did not result in larger maximum peak lumbar compression forces. Therefore, it was concluded that, from a biomechanical point of view, team lifting does not result in an additional risk for low back complaints in ironworkers.

Characteristic values of the lumbar load of manual patient handling for the application in workers' compensation procedures

BackgroundThe human spine is often exposed to mechanical load in vocational activities especially in combination with lifting, carrying and positioning of heavy objects. This also applies in particular to nursing activities with manual patient handling. In the present study a detailed investigation on the load of the lumbar spine during manual patient handling was performed.MethodsFor a total of 13 presumably endangering activities with transferring a patient, the body movements performed by healthcare workers were recorded and the exerted action forces were determined with regard to magnitude, direction and lateral distribution in the time course with a "measuring bed", a "measuring chair" and a "measuring floor". By the application of biomechanical model calculations the load on the lowest intervertebral disc of the lumbar spine (L5-S1) was determined considering the posture and action force data for every manual patient handling.ResultsThe results of the investigations reveal the occurrence of high lumbar load during manual patient handling activities, especially in those cases, where awkward postures of the healthcare worker are combined with high action forces caused by the patient's mass. These findings were compared to suitable issues of corresponding investigations provided in the literature. Furthermore measurement-based characteristic values of lumbar load were derived for the use in statement procedures concerning the disease no. 2108 of the German list of occupational diseases.ConclusionsTo protect healthcare workers from mechanical overload and the risk of developing a disc-related disease, prevention measures should be compiled. Such measures could include the application of "back-fairer" nursing techniques and the use of "technical" and" small aids" to reduce the lumbar load during manual patient handling. Further studies, concerning these aspects, are necessary.

Physical workload and accelerated occurrence of lumbar spine diseases: risk and rate advancement periods in a German multicenter case–control study

In a German multicenter case-control study of lumbar disc diseases, we calculated risk and rate advancement periods (RAP) for physical workload. Patients aged 25-70 years with clinically and radiologically verified lumbar disc herniation (286 males, 278 females) or symptomatic lumbar disc narrowing (145 males, 206 females) were compared with population control subjects (453 males and 448 females). For this analysis, all manual handling of objects of about ≥5 kg and postures with trunk inclination of ≥20 °, as assessed by technical experts, were included in the calculation of cumulative lumbar load, determined by biomechanical model calculations. Logistic regression analysis was applied to calculate RAP, adjusted for region. We found a steep positive dose-response relationship between age and lumbar disc narrowing among men as well as women; however, we did not find a monotonic increase in lumbar disc herniation risk with age. As a monotonic increase in disease risk with age constitutes a fundamental assumption underlying the RAP concept, we restricted our RAP analysis to cases with symptomatic lumbar disc narrowing. Among men, there was a positive dose-response relationship between the cumulative lumbar load and the acceleration of lumbar disc narrowing. In the highest exposure category, a RAP of 28.0 years [95% confidence interval (95% CI) 9.7-46.3 years] was found. Among women, the RAP was 8.8 years (95% CI 2.4-15.2 years) in the highest exposure category. This study emphasizes the conceptual importance of risk acceleration - causation not only comprises the occurrence of a disease (that without a specific exposure would not have occurred at all) but also the accelerated occurrence of a disease (that without exposure would have occurred later in life).

Measurement of Action Forces and Posture to Determine the Lumbar Load of Healthcare Workers During Care Activities with Patient Transfers

Moving patients or other care activities with manual patient handling is characterized by high mechanical load on the lumbar spine of healthcare workers (HCWs). During the patient transfer activity, the caregivers exert lifting, pulling, and pushing forces varying over time with respect to amplitude and direction. Furthermore, the caregivers distinctly change their posture and frequently obtain postures asymmetrical to the median sagittal plane, including lateral bending and turning the trunk. This paper describes a procedure to determine lumbar load during patient transfer supported by measurement techniques and an exemplary application; this methodology represents the basis of a complex research project, the third 'Dortmund Lumbar Load Study (DOLLY 3)'. Lumbar load was determined by simulation calculations using a comprehensive biomechanical model ('The Dortmunder'). As the main influencing factors, the hand forces of the caregiver exerted during typical patient transfers and the posture and movements of the HCW were recorded in laboratory studies. The action forces were determined three-dimensionally with the help of a newly developed 'measuring bed', two different 'measuring chairs', a 'measuring bathtub', and a 'measuring floor'. To capture the forces during transfers in or at the bed, a common hospital bed was equipped with an additional framework, which is attached to the bedstead and connected to the bedspring frame via three-axial force sensors at the four corners. The other measuring systems were constructed similarly. Body movements were recorded using three-dimensional optoelectronic recording tools and video recordings. The posture and force data served as input data for the quantification of various lumbar-load indicators.

Biomechanics of lumbar spine injury in young Australian fast bowlers

Cricket fast bowlers have a high incidence of serious lumbar injuries, such as lesions in the pars interarticularis. As lumbar loading is the causal mechanism of such injuries, the purpose...

An investigation in crashworthiness evaluation of aircraft seat cushions at extreme ranges of temperature

This paper obtains a Mathematical Dynamic Model (MADYMO) for occupant lumbar load evaluation under CFR Part 23 and 25 at extreme ranges of temperature. The validation of results is performed by full scale sled test results. Aircraft industries are using viscoelastic polyurethane foams as seat cushion. Visco-elastic foams bring not only more comfort to the passengers in long term sitting but it also maintains more safety during unpredicted crashes and hard landings. Aircraft seat cushions are exposed to varying temperature ranges during their life time. This fact has motivated aircraft industries to evaluate the seat cushion dynamic behavior at extreme ranges of temperatures in addition to what is mentioned in Federal Aviation Administration (FAA) Regulations at room temperature. This research provides a methodology based on simulation and modeling to eliminate, or at least, minimize the number of full scale dynamic sled tests defined by regulations for aircraft seats at extreme ranges of temperature.

Risk Factors for Lumbar Intervertebral Disc Herniation in Chinese Population

A case-control study of 4180 subjects was carried. To explore the risk factors of lumbar disc herniation in China. In China, along with the economic development, people's living environment and working conditions have undergone some tremendous changes, such as the accelerating life pace and competition. In this situation, it is important to know whether the risk factors of lumbar disc herniation have changed or not. This case-control study, including the possible social and psychological factors based on the literature, attempted to search the new risk factor, therefore provide better prevention measures for lumbar disc herniation. A total of 2010 hospitalized patients, diagnosed with lumbar disc protrusion by CT and/or MRI were selected as cases. A total of 2070 people from communities and hospitals, without history of low back pain and sciatica, were selected as controls. All patients and controls were investigated for their family history, occupational characters' smoking status, working psychosocial factors, etc. The risk factors were analyzed by multiple nonconditional logistic regression method. Family history (OR = 3.6) was the most important risk factor for lumbar disc protrusion in this study, followed by lumbar load (OR = 2.1), hard-working (OR = 1.8), and time urgency (OR = 1.1). Additionally, physical exercises (OR = 0.5) and bed characteristics (OR = 0.4) appeared to be the protective factors for lumbar disc protrusion. After stratified by age, family history (OR = 14.5), occupational character (OR = 5.2), and physical exercises (OR = 0.2) stronger association with lumbar disc protrusion was seen in subjects younger than 30 years. In subjects from 30 to 55 years, family history (OR = 5.1), lumbar load (OR = 1.91), hard-working (1.9), physical exercises (OR = 0.5), time urgency (OR = 1. 3), bed characteristics (OR = 0.4) were significantly important. In subjects older than 55 years, lumbar load (OR = 2.9) and bed characteristics (OR = 0.4) were closely related to lumbar disc protrusion. Family history, lumbar load, hard-working, and time urgency are the major risk factors for lumbar disc herniation, and physical exercises and sleeping on the hard bed might be the protective factors.

Cumulative occupational lumbar load and lumbar disc disease – results of a German multi-center case-control study (EPILIFT)

BackgroundThe to date evidence for a dose-response relationship between physical workload and the development of lumbar disc diseases is limited. We therefore investigated the possible etiologic relevance of cumulative occupational lumbar load to lumbar disc diseases in a multi-center case-control study.MethodsIn four study regions in Germany (Frankfurt/Main, Freiburg, Halle/Saale, Regensburg), patients seeking medical care for pain associated with clinically and radiologically verified lumbar disc herniation (286 males, 278 females) or symptomatic lumbar disc narrowing (145 males, 206 females) were prospectively recruited. Population control subjects (453 males and 448 females) were drawn from the regional population registers. Cases and control subjects were between 25 and 70 years of age. In a structured personal interview, a complete occupational history was elicited to identify subjects with certain minimum workloads. On the basis of job task-specific supplementary surveys performed by technical experts, the situational lumbar load represented by the compressive force at the lumbosacral disc was determined via biomechanical model calculations for any working situation with object handling and load-intensive postures during the total working life. For this analysis, all manual handling of objects of about 5 kilograms or more and postures with trunk inclination of 20 degrees or more are included in the calculation of cumulative lumbar load. Confounder selection was based on biologic plausibility and on the change-in-estimate criterion. Odds ratios (OR) and 95% confidence intervals (CI) were calculated separately for men and women using unconditional logistic regression analysis, adjusted for age, region, and unemployment as major life event (in males) or psychosocial strain at work (in females), respectively. To further elucidate the contribution of past physical workload to the development of lumbar disc diseases, we performed lag-time analyses.ResultsWe found a positive dose-response relationship between cumulative occupational lumbar load and lumbar disc herniation as well as lumbar disc narrowing among men and women. Even past lumbar load seems to contribute to the risk of lumbar disc disease.ConclusionAccording to our study, cumulative physical workload is related to lumbar disc diseases among men and women.

Back disorders and lumbar load in nursing staff in geriatric care: a comparison of home-based care and nursing homes

BackgroundBack pain is one of the most frequent complaints in the nursing profession. Thus, the 12-month prevalence of pain in the lumbar spine in nursing staff is as high as 76%. Only a few representative studies have assessed the prevalence rates of back pain and its risk factors among nursing staff in nursing homes in comparison to staff in home-based care facilities. The present study accordingly investigates the prevalence in the lumbar and cervical spine and determines the physical workload to lifting and caring in geriatric care.Methods1390 health care workers in nursing homes and home care participated in this cross sectional survey. The nursing staff members were examined by occupational physicians according to the principals of the multistep diagnosis of musculoskeletal disorders. Occupational exposure to daily care activities with patient transfers was measured by a standardised questionnaire. The lumbar load was calculated with the Mainz-Dortmund dose model. Information on ergonomic conditions were recorded from the management of the nursing homes. Comparisons of all outcome variables were made between both care settings.ResultsComplete documentation, including the findings from the occupational physicians and the questionnaire, was available for 41%. Staff in nursing homes had more often positive orthopaedic findings than staff in home care. At the same time the values calculated for lumbar load were found to be significant higher in staff in nursing homes than in home-based care: 45% vs. 6% were above the reference value. Nursing homes were well equipped with technical lifting aids, though their provision with assistive advices is unsatisfactory. Situation in home care seems worse, especially as the staff often has to get by without assistance.ConclusionsFuture interventions should focus on counteracting work-related lumbar load among staff in nursing homes. Equipment and training in handling of assistive devices should be improved especially for staff working in home care.

Frequency of cyclic lumbar loading is a risk factor for cumulative trauma disorder

Epidemiologic studies indicate that repetitive (cyclic) occupational activities lead to a cumulative trauma disorder (CTD), and the frequency or velocity of the movement is one of the risk factors. Experimental neurophysiological evidence to confirm the epidemiology is not available. The response of the multifidus muscles to cyclic loading in anterior lumbar flexion-extension was assessed to test the hypothesis that high-frequency loading may induce an acute neuromuscular disorder leading to CTD. Two groups of feline preparations were subjected to cyclic loading with a peak of 20 N: one at 0.25 HZ and the second at 0.5 HZ, with an equal number of cycles. Electromyogram (EMG), lumbar displacement and load were recorded throughout the loading periods and during single-cycle tests over a 7-hour rest period following the load-rest sessions. A model was developed to quantify the creep and neuromuscular responses, and analysis of variance (ANOVA) was applied to assess significance of the results. The group exposed to 0.5 HZ exhibited spontaneous spasms followed by sustained spasms during the loading periods. During the 7-hour recovery period, a significant (P < 0.001) delayed hyperexcitability as well as sustained spasms of the multifidi were present in the last 5 hours, confirming a significant (P < 0.024 to P < 0.042) acute neuromuscular disorder. High-frequency cyclic loading of the lumbar spine may trigger a severe acute neuromuscular disorder, as evidenced by the sustained spasms and delayed hyperexcitability, and should be considered as a risk factor. We suggest that workers avoid high-frequency exposure to cyclic activity in order to prevent the development of cumulative trauma disorder.

Load on the lumbar spine of flight attendants during pushing and pulling trolleys aboard aircraft

Flight attendants report on high physical load and complaints particularly focussing on the lower back. These findings are mainly ascribed to pushing and pulling of trolleys during the ascent and descent flight phases. Within an interdisciplinary experimental study, the load on the lumbar spine of flight attendants during trolley handling aboard aircraft was analysed based on laboratory measurements regarding posture and exerted forces as well as on subsequent biomechanical model calculations. Forces and moments of force at the lumbosacral disc were quantified for 458 manoeuvres performed by 25 flight attendants in total (22 female, 3 male). Lumbar load varies according to handling mode (pushing, pulling), floor gradient (0°, 2°, 5°, 8°), trolley type (half-, full-size trolley), trolley loading (empty, medium, full) and, in addition, according to individual execution technique. For each of the resulting 48 task configurations, lumbar load was evaluated with respect to potential biomechanical overload by applying work-design recommendations for disc compression and moment of force. Irrespective of floor inclination, trolley weight and individual performance, pushing of small trolleys is combined with acceptable lumbar load, pulling with critical load. Pushing or pulling large trolleys occasionally yield to critical lumbar load, in particular, when heavy or heaviest containers are moved on relatively steep or steepest surfaces. To diminish overload risk relevantly, top-edge grasp positions should be avoided for pulling of half-size trolleys, whereas for the other cases, grasping at the upper edge of the trolley is recommended. Relevance to industry The provided study illustrates lumbar load of flight attendants during trolley handling aboard aircraft for typical task conditions and individual execution techniques. Specified hints for work design regarding posture and grasp position enable to avoid biomechanical low-back overload for flight attendants. Furthermore, trolley properties may be reconsidered, regular maintenance of rollers should be guaranteed.

Short rest between cyclic flexion periods is a risk factor for a lumbar disorder

The epidemiology identifies cyclic lumbar loading as a risk factor for cumulative trauma disorder. Experimental biomechanical and physiological confirmation is lacking. The objective of this study was to asses the impact of different rest durations applied between periods of cyclic loading on the development of an acute lumbar disorder which, if continued to be subjected to loading, may develop into a cumulative disorder. Three groups of in vivo feline preparations were subjected to six sequential 10 min loading periods of cyclic lumbar flexion at 40 N with a frequency of 0.25 Hz applied to the L-4/5 level. The rest durations varied from 5 min in the first group, to 10 min in the second and to 20 min in the third. Reflexive EMG from the multifidi and lumbar displacement were used to identify significant (P<0.001) effects of time and rest duration for post-load EMG and displacement. Single-cycle test were performed hourly for 7 h post-loading to assess recovery. A model developed earlier was applied to represent the experimental data. The groups allowed 5 and 10 min rest exhibited an acute neuromuscular disorder expressed by a significant (P<0.001) delayed hyperexcitability 2-3 h into the 7 h recovery period with the intensity of the hyperexcitability significantly higher (P<0.001) for the group allowed only 5 min rest. The group allowed 20 min rest had a slow, uneventful recovery, free of delayed hyperexcitability. Occupational and sports activities requiring repetitive (cyclic) loading of the lumbar spine may be a risk factor for the development of a cumulative lumbar disorder and may require sufficient rest, as much as twice as long as the loading period, for prevention. Comparison to similar data for static lumbar loading shows that cyclic loading is more deleterious than static loading, requiring more rest to offset the negative effect of the repeated acts of stretch.