Lumbar spinal loads and lumbar muscle forces evaluation with various lumbar supports and backrest inclination angles in driving posture.

PURPOSE: The low back pain of professional drivers could be linked to excessive lumbar load. This study aims at developing a musculoskeletal model to study the lumbar spinal loads and lumbar muscle forces of the human body in driving posture, so as to contribute to a better understanding of low back pain and to improve the design of vehicle seats. METHODS: A standing musculoskeletal model, including limbs, head and neck, that can reflect several activities of daily living was established based on the Christophy spine model. The model was then validated by comparing the calculated lumbar loads and muscle forces to the experimental data in the previous studies. Referring to radiology studies, the musculoskeletal model was adjusted into different driving postures with several different lumbar supports (0, 2 and 4 cm) and inclinations of the backrest (from 23° to 33°, by 2° intervals). The lumbar biomechanical load with various lumbar supports and backrest inclination angles was calculated. RESULTS: The results showed that the overall lumbar spinal load and lumbar muscle force with 4 cm lumbar support were reduced by 11.30 and 26.24%. The lumbar spinal loads and lumbar muscle forces increased first and then decreased with the increase in backrest inclination angles from 23° to 33°. The lumbar biomechanical load varied slightly with the backrest inclination angles from 29° to 33°. CONCLUSIONS: There are two findings: (i) the lumbar spinal loads at the L3-L4, L4-L5 and L5-S1, and lumbar muscle forces decreased obviously with the 4 cm lumbar support, while the seat cushion inclination angle was set to 10°. (ii) The recommended backrest inclination angles are 29° to 33° with a 10° seat cushion to the horizontal, which can keep a low level of the lumbar spinal loads and lumbar muscle forces. This study could be used to explain the association between drivers' sitting posture and the lumbar load change, and provide a reference for the prevention of low back pain.

Design and Characterization of a Low-Cost and Efficient Torsional Spring for ES-RSEA.

The design of torsional springs for series elastic actuators (SEAs) is challenging, especially when balancing good stiffness characteristics and efficient torque robustness. This study focuses on the design of a lightweight, low-cost, and compact torsional spring for use in the energy storage-rotary series elastic actuator (ES-RSEA) of a lumbar support exoskeleton. The exoskeleton is used as an assistive device to prevent lower back injuries. The torsion spring was designed following design for manufacturability (DFM) principles, focusing on minimal space and weight. The design process involved determining the potential topology and optimizing the selected topology parameters through the finite element method (FEM) to reduce equivalent stress. The prototype was made using a waterjet cutting process with a low-cost material (AISI-4140-alloy) and tested using a custom-made test rig. The results showed that the torsion spring had a linear torque-displacement relationship with 99% linearity, and the deviation between FEM simulation and experimental measurements was less than 2%. The torsion spring has a maximum torque capacity of 45.7 Nm and a 440 Nm/rad stiffness. The proposed torsion spring is a promising option for lumbar support exoskeletons and similar applications requiring low stiffness, low weight-to-torque ratio, and cost-effectiveness.

A newly developed floor chair placed on an office chair reduces lumbar muscle fatigue by cyclically changing its lumbar supporting shape.

[Purpose] This study investigated lumbar muscle fatigue before and after maintaining a seated position for one hour, lumbar and pelvic inclination angle change, in subjects with and without active lumber support. [Subjects and Methods] Fourteen healthy subjects randomized into two groups sat on a floor chair, placed on an office chair, that cyclically changed its lumbar supporting shape to provide active lumbar support (ALS) or no ALS for one hour. Before and after, we measured the frequency of muscle waveforms of the trunk extensor muscles when the subjects lifted an object weighing 10% of their body weight, using both hands while seated. In addition, ROMt (Range of motion test) of trunk rotation, degree of fatigue and muscle stiffness were analyzed. [Results] Muscle frequency while lifting the weight decreased significantly without ALS compared to with ALS. Mean muscle stiffness increased, ROMt decreased in desk work task significantly without ALS compared to with ALS. [Conclusion] These results suggest that the lumbar muscles became fatigued, because low frequencies, increased muscle stiffness, and decreased ROMt without ALS. We suggest lumbar muscle fatigue was maintained low for subjects seated in a chair with ALS.

Do users desire symmetrical lumbar supports in task seating?

This research was designed to objectively investigate the desired low back (lumbar) support in a task chair; specifically by allowing a user to self-select the magnitude and location of support. An experimental chair built specifically for this study allowed the users to remotely adjust 35 diodes to achieve their desired level of support. Pressure mapping was used to measure the interface pressure at the user-seat back interface. It was determined that 73.8% of the 201 participants in this study, self-selected asymmetrical lower back support that was at least 20% greater on one side vs. the other. Additionally, 16.9% of the participants self-selected support on one side which was at least twice that of the other side. Contrary to popular practice, participants were found to prefer asymmetric support in the lower back region. It is anticipated that the culmination of this research will aid chair manufacturers in designing adaptable back rests. Practitioner Summary: Most current lumbar supports are designed to move vertically and to symmetrically increase or decrease in firmness as per a user's adjustment. This investigation highlights that participants tended to select asymmetrical lumbar support, and as such, designers should consider providing lumbar supports that provide the desired support at appropriate locations.

Chair Size Design Based on User Height.

General principles derived from anatomical studies of human body sizes should be applied to chair designs. Chairs can be designed for a specific user or a particular group of users. Universal chairs for public spaces should be comfortable for the largest possible group of users and should not be adjustable, such as office chairs. However, the fundamental problem is that the anthropometric data available in the literature either come from many years ago and are out of date or do not provide a complete set of all the dimensional parameters of a sitting human body position. This article proposes a way to design chair dimensions solely based on the height range of the intended chair users. For this purpose, based on literature data, the main structural dimensions of the chair were assigned to the appropriate anthropometric body measurements. Furthermore, calculated average body proportions for the adult population overcome the incompleteness, outdated and burdensome access to anthropometric data and link the main chair design dimensions to one easily accessible anthropometric parameter: human height. This is achieved by seven equations describing the dimensional relations between the chair's essential design dimensions and human height or even a height range. The result of the study is a method of determining the optimal functional dimensions of a chair for a chosen range of sizes of its future users based only on users' height range. Limitations of the presented method: the calculated body proportions are correct only for people with a standard body proportion characteristic of adults, i.e., they exclude children and adolescents up to 20 years of age, seniors, and people with a body mass index exceeding 30.

[Preliminary observation on the clinical application of rehabilitation support for lumbar disc herniation based on 3D printing technology].

OBJECTIVE: To analyze the important effect of 3D printing personalized lumbar support on lumbar pain and lumbar function in patients with lumbar disc herniation. METHODS: From October 2018 to May 2021, 60 patients initially diagnosed with lumbar disc herniation were selected and divided into an observation group and a control group, with 30 patients in each group. Among them, there were 18 males and 12 females in the observation group;the age ranged from 24 to 56 years old, with an average of (45.23±6.07) years old. The course of disease ranged from 1 to 24 months, with an average of(6.25±0.82) months, and rehabilitation treatment was carried out by wearing 3D printed personalized lumbar support. There were 19 males and 11 females in the control group;the age ranged from 25 to 57 years old, with an average of (42.78±7.58) years old. The course of disease ranged from 1 to 24 months, with an average of (6.72±1.36) months, and rehabilitation treatment is carried out by wearing traditional lumbar protective equipment. The Japanese Orthopaedic Association (JOA) scores, lumbar Oswestry dysfunction index (ODI) and visual analogue scale (VAS) were evaluated and compared between the two groups before and 1 course after treatment (3 weeks). RESULTS: There was no statistically significant difference in JOA, ODI, and VAS between two groups before treatment (P>0.05). After one course of treatment (3 weeks), JOA scores of both groups was increased compared to before treatment (P<0.05), while ODI and VAS decreased compared to before treatment (P<0.05). After treatment, JOA score of observation group was higher than that of control group (P<0.05), while ODI and VAS scores were lower than those of control group. No adverse events occurred in both groups. CONCLUSION: The application of 3D printing personalized lumbar support can effectively alleviate the pain of patients with lumbar disc herniation and improve their lumbar function of patients.

Influence of seat lumbar support adjustment on muscle fatigue under whole body vibration: An in vivo experimental study.

BACKGROUND: In order to alleviate muscle fatigue and improve ride comfort, many published studies aimed to improve the seat environment or optimize seating posture. However, the effect of lumbar support on the lumbar muscle of seated subjects under whole body vibration is still unclear. OBJECTIVE: This study aimed to investigate the effect of lumbar support magnitude of the seat on lumbar muscle fatigue relief under whole body vibration. METHODS: Twenty healthy volunteers without low back pain participated in the experiment. By measuring surface electromyographic signals of erector spinae muscles under vibration or non-vibration for 30 minutes, the effect of different lumbar support conditions on muscle fatigue was analyzed. The magnitude of lumbar support d is assigned as d1= 0 mm, d2= 20 mm and d3= 40 mm for no support, small support and large support, respectively. RESULTS: The results showed that lumbar muscle activation levels vary under different support conditions. For the small support case (d2= 20 mm), the muscle activation level under vibration and no-vibration was the minimum, 42.3% and 77.7% of that under no support (d1= 0 mm). For all support conditions, the muscle activation level under vibration is higher than that under no-vibration. CONCLUSIONS: The results indicate that the small support yields the minimum muscle contraction (low muscle contraction intensity) under vibration, which is more helpful for relieving lumbar muscle fatigue than no support or large support cases. Therefore, an appropriate lumbar support of seats is necessary for alleviating lumbar muscle fatigue.

Non-rigid lumbar supports for the management of non-specific low back pain: A literature review and meta-analysis.

BACKGROUND: Clinical practice guidelines for non-specific low back pain do not recommend the use of non-rigid lumbar supports (NRLSs) despite the publication of several positive randomized controlled studies. OBJECTIVE: We conducted a systematic review with meta-analysis to assess the efficacy of NRLSs in the treatment and prevention of non-specific low back pain. METHODS: We searched for reports of randomized controlled trials in PubMed, Cochrane Library, EMBASE, Science Direct and Pedro databases. Data were analyzed by disease stage (acute, subacute, and chronic) and type of prevention (primary and secondary). The analysis of methodological quality involved the Physiotherapy Evidence Database (PEDro) scale. RESULTS: Of the 1581 records retrieved, only 4 full-text articles were included, with 777 patients: 378 in the NRLS group, and 348 in the control group. NRLSs conferred greater amelioration of disability (effect size -0.54, 95% CI -0.90; -0.17) and pain (-0.29, -0.46; -0.12) than standard management. Insufficient data prevented a comparison of the efficiency for acute, subacute and recurrent low back pain as well as meta-regression of responder phenotypes (sociodemographic and other patient characteristics). CONCLUSION: We demonstrated the overall efficacy of NRLSs for both disability and pain. However, further studies are needed to assess which patients can benefit the most from lumbar supports based on patient phenotype and the characteristics of low back pain. PROSPERO (CRD42018109855).

An Indication-Based Concept for Stepwise Spinal Orthosis in Low Back Pain According to the Current Literature.

BACKGROUND: The current literature is not conclusive for spinal orthosis treatment in low back pain. Therefore, two questions have to be answered: Does the current literature support the indication of spinal orthosis treatment in low back pain? Which treatment concept can be derived from the result? METHOD: The 30 highest-rated literature citations (PubMed: best match, 30 December 2021) dealing with low back pain and spine orthosis were included in the study. Excluded were all articles related to Kinesio Taping, scoliosis, physical exercise, or dealing with side effects and unrelated to treatment effect. Thus, the literature list refers only to "low back pain and spine orthoses". These articles were analyzed according to the PRISMA criteria and divided according to "specific diagnosis", when the cause of pain was explained (group A), or when "specific diagnosis is not given" (group B). The articles were also distinguished by the information about the orthosis. Articles with biomechanical information about the function of the orthoses were called "diagnosis-based orthosis" (group C). All other articles were part of the group "unspecific orthotic treatment" (group D). The results were compared to each other in terms of effectiveness. According to anatomical causes, a concept of orthosis selection depending on diagnosis of low back pain for clinical practice was developed. The risk of bias lies in the choice of the MESH terms. The synthesis of the results was a clinical treatment concept based on findings from the current literature. RESULTS: The literature citations with 1749 patients and 2160 citations of literature were processed; 21 prospective clinical or biomechanical studies and 9 review articles were included. The combination of literature citations according to "specific diagnosis" (group A) and "diagnosis based orthosis" (group C) was very likely to lead to a therapeutic effect (seven articles). No positive effect could be found in four articles, all dealing with postoperative treatment. When "specific diagnosis is not given" (group B) and combined with "unspecific orthotic treatment" (group D), therapy remained without measurable effect (15 articles). An effect was described in four articles (three biomechanical studies and one postoperative study). In review articles, according to specific diagnosis, only one article dealt with fractures and another with stenosis. In all review articles where specific diagnosis was not given, no effect with spine orthoses could be found. Using this knowledge, we created a clinical treatment concept. The structure was based on diagnosis and standardized orthoses. According to pain location and pathology (muscle, intervertebral disc, bone, statics, postoperative) the orthoses were classified to anatomical extent and the mechanical limitation (bandage, bodice, corset, orthosis with shoulder straps and erecting orthosis). CONCLUSION: The effectiveness of spinal orthoses could not be deduced from the current literature. The most serious limitation was the inconsistency of the complaint and the imprecise designation of the orthoses. INTERPRETATION: Articles with a precise allocation of the complaint and a description of the orthosis showed a positive effect. The treatment concept presented here is intended to provide a basis for answering the question concerning the effectiveness of spinal orthoses as an accompanying treatment option in low back pain.

Influence of an on-body lifting aid (HAL® for Care Support) on kinematics during repetitive lifting in healthy men.

Work-related lower back pain (LBP) leads to socio-economic burden and demands solutions. The hybrid assistive limb (HAL) for Care Support (Cyberdyne Inc., Ibaraki, Japan) is an active on-body lifting aid to assist joint motion according to the wearer's voluntary motor drive to reduce the lumbar load. A few studies investigated HAL and stated efficacy in terms of enhanced performance and reduced fatigue, yet the question remained if the use of HAL may result in a different execution of movement, for example by influencing the kinematics of the lower extremities. The aim of this study was to determine the influence of HAL on kinematics of the lower limbs and the spinal column during repetitive freestyle symmetrical lifting. Kinematic data was recorded by an inertial measurement unit sensor system in 11 healthy men lifting and lowering a 19.5 kg barbell under three conditions (no HAL, HAL Level 3/5, HAL Level 5/5). Outcome parameters were maximum and minimum angles as well as range of motion (ROM) of thoracic spine, lumbar spine, hip- and knee joint in sagittal plane. We found a significantly decreased ROM of the lumbar spine as well as a significantly reduced maximum and minimum thorax extension when starting lifting and in upright position after lifting, respectively, while using HAL. Influence of HAL on the kinematics of the lower limbs was not significant. Differences between both evaluated HAL conditions were not significant. This study proved limited lumbar spine ROM and reduced thorax extension without alterations of lower limbs kinematics when using HAL. This might potentially decrease the risk of work-related LBP.

Partitioning the total seatback reaction force amongst the lumbar spine motion segments during simulated rear-impact collisions.

Purpose. This study aimed to determine how the seatback force is distributed across lumbar spine motion segments during a simulated low-velocity rear-impact collision with and without the application of mechanical lumbar support. Methods. A ferroresistive pressure-sensing system was used during simulated rear-impact collisions (ΔV = 7.66 km/h). Total seatback reaction force was derived from pressure recordings as the product of calibrated pressure outputs and sensel areas. The three-dimensional position of the pressure mat and the lumbar spinous processes were tracked and then used to extract the seatback force that was applied to the lumbar motion segments. Results. On average, 77% (637 N) and 53% (430 N) of the total seatback force was applied directly to the lumbar spine with and without lumbar support, respectively (p < 0.001). In addition to four of five individual motion segments bearing a greater force with lumbar support (p < 0.029), the distribution of the total lumbar force was found to be significantly different between support type conditions. Conclusions. Although lumbar supports can alter the magnitude and distribution of shear force applied to the lumbar spine during low-velocity rear-impact collisions, they do not appear to elevate the injury risk.

Assessment of the Range of Movement of the Lower Limb in Sport: Advantages of the ROM-SPORT I Battery.

Range of movement (ROM) assessment is an important strategy to increase physical-technical performance and minimize the risk of sports-related injuries. Currently, there is no consensus regarding which ROM assessment method is the most appropriate. The main objective of this study was to perform a systematic review of the test batteries available for the assessment of lower limb ROM; additionally, we compare the ROM-SPORT I battery with those previously reported in the literature. The systematic review was conducted following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines. The identification of publications was made by using the databases SciELO, Medline, Scopus, PubMed, and Web of Science. Based on the inclusion criteria, sixteen publications were selected and analyzed. The ROM-SPORT I battery is the most valid of the analyzed methods. This battery evaluates the ROM of eleven lower limb movements. The inclinometer with a telescopic arm and a box is a simpler, more comfortable, and faster procedure than others. The Lumbosant support and use of two examiners are essential to avoid compensatory movements to obtain reliable measurements during ROM assessment. The ROM-SPORT I is a field-based battery of tests that may be used by sports professionals, clinics, and researchers in applied settings to accurately assess and monitor lower extremity ROM.

Muscle Synergies During Repetitive Stoop Lifting With a Bioelectrically-Controlled Lumbar Support Exoskeleton.

Lower back problems are common in the world, which leads to the development of various lumbar support exoskeletons to alleviate this problem. In general, previous studies evaluating lumbar support devices quantified assistance by reporting the reduction in back muscle activity and perceived fatigue. However, despite the beneficial effects of such devices, the effects of using such exoskeletons on muscle coordination are not well-studied. In this study, we examined the short-term change in muscle coordination of subjects using a bioelectrically-controlled lumbar support exoskeleton in a fatiguing stoop lifting task with muscle synergy analysis. Results indicate that muscle coordination changes were dominated by changes in timing coefficients, with minimal change in muscle synergy vectors. Analysis on muscle coordination changes would be useful to design future generations of exoskeletons.

Effect of a prototype lumbar spinal stenosis belt versus a lumbar support on walking capacity in lumbar spinal stenosis: a randomized controlled trial.

BACKGROUND CONTEXT: Lumbar spinal stenosis (LSS) can impair blood flow to the spinal nerves giving rise to neurogenic claudication and limited walking ability. Reducing lumbar lordosis can increases the volume of the spinal canal and reduce neuroischemia. We developed a prototype LSS belt aimed at reducing lumbar lordosis while walking. PURPOSE: The aim of this study was to assess the short-term effectiveness of a prototype LSS belt compared to a lumbar support in improving walking ability in patients with degenerative LSS. STUDY DESIGN: This was a two-arm, double-blinded (participant and assessor) randomized controlled trial. PATIENT SAMPLE: We recruited 104 participants aged 50 years or older with neurogenic claudication, imaging confirmed degenerative LSS, and limited walking ability. OUTCOME MEASURES: The primary measure was walking distance measured by the self-paced walking test (SPWT) and the primary outcome was the difference in proportions among participants in both groups who achieved at least a 30% improvement in walking distance from baseline using relative risk with 95% confidence intervals. METHODS: Within 1 week of a baseline SPWT, participants randomized to the prototype LSS belt group (n=52) and those randomized to the lumbar support group (n=52) performed a SPWT that was conducted by a blinded assessor. The Arthritis Society funded this study ($365,000 CAN) with salary support for principal investigator funded by the Canadian Chiropractic Research Foundation ($500,000 CAN for 5 years). RESULTS: Both groups showed significant improvement in walking distance, but there was no significant difference between groups. The mean group difference in walking distance was -74 m (95% CI: -282.8 to 134.8, p=.49). In total, 62% of participants wearing the prototype LSS belt and 82% of participants wearing the lumbar support achieved at least 30% improvement in walking distance (relative risk, 0.7; 95% CI: 0.5-1.3, p=.43). CONCLUSIONS: A prototype LSS belt demonstrated significant improvement in walking ability in degenerative LSS but was no better than a lumbar support.

A randomized controlled trial comparing the long-term use of soft lumbosacral orthoses at two different pressures in patients with chronic nonspecific low back pain.

BACKGROUND: There is concern that wearing soft lumbosacral orthoses for prolonged periods may impair motor function. Moreover, the pressure applied by lumbosacral orthoses on the abdominal wall is usually ignored when these orthoses are prescribed. METHOD: In this randomized controlled trial study, 48 patients with chronic nonspecific low back pain were randomly divided into high pressure, normal pressure and control groups. All groups received medication for 4 weeks. The normal pressure and high pressure groups, in addition to medication, used soft lumbosacral orthoses at normal pressure and 50% increased pressure, respectively. Motor function outcome measures were strength, endurance, proprioception and electromyographic activity of the trunk muscles. Clinical outcome measures were pain and disability, which were evaluated in two sessions before and after a 4-week interval. FINDINGS: Isometric strength, endurance and most of the electromyographic parameters were generally unaffected by wearing the lumbosacral orthosis. Pain improved in all groups, and disability and proprioception improved in the high pressure and normal pressure groups. Between-group differences in these three measures indicated better results in the lumbosacral orthoses groups than in the control group. The improvements in pain and proprioception were significantly greater in the high pressure group than the normal pressure group. INTERPRETATION: Long-term use of lumbosacral orthoses had no significant adverse effects on motor function or clinical factors in patients with chronic low back pain. Increasing lumbosacral orthosis tightness may improve motor functioning and the clinical efficacy of the orthosis. CLINICAL TRIAL REGISTRATION NUMBER: Code: IRCT201708192391N38.

Anterior chest support, muscular activity and subjective rating of exertion during microtome sectioning.

Seven females, six laboratory assistants, participated in the experimental part of the study. The level of muscular activity in different sitting work postures was recorded, using surface electrodes, as full-wave-rectified and low-pass filtered EMG, and normalised. The laboratory assistants also rated the degree of exertion in four different body regions during their ordinary microtome sectioning work, comparing the use of anterior chest support with the use of their usual chair with lumbar support. The use of anterior chest support reduced the muscular activity in the lumbar back muscles but increased it in the shoulder muscles. Perceived exertion in the neck, shoulders and thoracic back regions increased. Anterior chest support does not seem to solve the problem of neck- and-shoulder load-elicited pain during the work of preparing laboratory sections.