Seat Position Research Articles

Analysis of ride comfort of high-speed train based on a train-seat-human model in the vertical direction

A rigid-flexible coupled train-seat-human model was developed for studying ride comfort of rail vehicles. The weighted acceleration r.m.s. value at the seat pan was used for assessing ride comfort. The contribution of different modes of the carbody to ride comfort was defined from the perspective of power spectral density. The role of first bending mode was more important than other bending modes when bogie and seat positions are far from the nodes of first bending mode. Under this situation, the bogie spacing filter effect of first bending mode can be adopted to predict peaks and troughs of the equivalent acceleration on the floor or human-seat interface varying with speed or first bending frequency. The incorporation of human-seat system was necessary in order to accurately evaluate ride comfort. The ride comfort exhibited a global trend of improvement with increased bending rigidity or reduced speed. Increasing the damping ratio of bending modes improved ride comfort effectively. Increasing stiffness or decreasing damping of human-seat vertical contact on the seat pan worsened ride comfort. Equivalent accelerations at symmetrical seat positions showed analogous tendency as the speed. Ride comfort was worst at two ends whatever the speed was, followed by carbody centre at high speed.

Wheelchair Seated Posture and Health Outcomes of Older Veterans in Community Living Centers.

Nursing home residents sit in wheelchairs (WCs) for extended periods, often with slumped posture. They often experience pneumonia, pressure ulcers, and pain. This study described WC seated posture with its selected predictors and outcomes in the nursing home environment, throughout the daytime hours of 1 day. This observational study (n = 45) in two Veterans Administration Community Living Centers introduced a new measure of WC fit and described WC seated posture of older Veterans, with selected predictors and outcomes. Wheelchair seated posture was predicted by cognitive status, WC fit, WC skills, and duration of sitting, but not by level of sitting ability. Poor posture measured by the Seated Posture Scale was associated with pain. Highest interface pressures measurable were seen in peak pressure index (PPI = 200 mm Hg), indicating risk of pressure injury. Veterans often denied discomfort, possibly lowering overall pain scores, while reporting severe pain in specific body parts. Wheelchair seated posture was predicted by cognitive status, WC fit, WC skills, and duration of sitting. Poor posture was associated with pain, and poor posture was an outcome of poor WC fit. Poor WC fit in this study supported earlier findings in non-Veterans Administration nursing homes.

A Wearable Device Based on a Fiber Bragg Grating Sensor for Low Back Movements Monitoring.

Low back pain (LBP) is one of the musculoskeletal disorders that most affects workers. Among others, one of the working categories which mainly experiences such disease are video terminal workers. As it causes exploitation of the National Health Service and absenteeism in workplaces, LBP constitutes a relevant socio-economic burden. In such a scenario, a prompt detection of wrong seating postures can be useful to prevent the occurrence of this disorder. To date, many tools capable of monitoring the spinal range of motions (ROMs) are marketed, but most of them are unusable in working environments due to their bulkiness, discomfort and invasiveness. In the last decades, fiber optic sensors have made their mark allowing the creation of light and compact wearable systems. In this study, a novel wearable device embedding a Fiber Bragg Grating sensor for the detection of lumbar flexion-extensions (F/E) in seated subjects is proposed. At first, the manufacturing process of the sensing element was shown together with its mechanical characterization, that shows linear response to strain with a high correlation coefficient (R2 > 0.99) and a sensitivity value (Sε) of 0.20 nm∙mε−1. Then, the capability of the wearable device in measuring F/E in the sagittal body plane was experimentally assessed on a small population of volunteers, using a Motion Capture system (MoCap) as gold standard showing good ability of the system to match the lumbar F/E trend in time. Additionally, the lumbar ROMs were evaluated in terms of intervertebral lumbar distances (Δ) and angles, exhibiting moderate to good agreement with the MoCap outputs (the maximum Mean Absolute Error obtained is ~16% in detecting ). The proposed wearable device is the first attempt for the development of FBG-based wearable systems for workers’ safety monitoring.

Improving the utility of high-resolution manometry for the diagnosis of defecatory disorders in women with chronic constipation.

We compared the utility of existing and modified versions of high-resolution manometry for diagnosing defecatory disorders (DD). In 64 healthy and 136 constipated women, we compared left lateral (LL) and seated manometry, and analyzed with existing (ManoView™) and new methods, for discriminating between constipated patients with normal and prolonged rectal balloon expulsion time (BET). In both positions, the rectoanal gradient (RAG) and, for the new analysis, the pressure topography pattern during evacuation were used to discriminate between constipated patients without and with DD. The BET was prolonged, suggestive of a DD, in 52 patients (38%). During evacuation, rectoanal pressures and the RAG were greater in the seated than the LL position (P≤.001). The new analysis identified 4 rectoanal pressure patterns. In the seated position, the BET was associated with the pattern (P=.0001), being prolonged in, respectively, 45%, 15%, 53%, and 0% of patients with minimal change, anal relaxation, paradoxical contraction, and transmission. Within each pattern, the RAG was greater (ie, less negative, P<.0001) in patients with a normal than a prolonged BET. Compared to the ManoView™ RAG in the LL position, the integrated analysis (ie, pattern and new RAG) in the LL position (P<.01) and the seated ManoView™ gradient (P=.02) were more effective for discriminating between constipated patients without and with DD. Anorectal HRM ideally should be performed in the more physiological seated position and analyzed by a two-tier approach, which incorporates the overall pattern followed by the rectoanal gradient. These findings reinforce the utility of manometry for diagnosing DD.

A Novel Approach towards Early Detection of Obliteration in Lumbar Lordosis.

The millennial age group (18 to 30 years) spend at least 6 hours sitting, either in college or at their workspace. High screen time as a routine, is the major cause for numerous spinal problems. Despite the wide research carried out on postural abnormalities, there exists numerous unrequited queries with regards to lumbar lordosis estimations, due to indeterminate parameters such as age, gender, lifestyle and diet. This work emphasizes the proficient method by observing the posture of a person for early detection of obliteration in Lumbar Lordosis. This further contributes to efficient diagnosis and treatment of spine ailments. With a novel approach to hardware using the myRIO hardware coupled with LabVIEW for interactive interface, the calibration is enhanced using machine learning (ML) - kNN Classifier. The use of machine learning accounts for the variations in the ideal angles of segmented sagittal measures with respect to different subjects. The device is developed to be a non-invasive, user friendly instrument to analyse the casual seated posture trends of the subject. The male subjects are expected to show the tilt angles in the range of -16.3 to -17.2 degrees and similar threshold for females are -15.8 to -16.8 degrees. Out of 120 subjects taken into consideration, the device could accurately classify subjects with obliterated or normal lumbar lordosis). An accuracy and f1- score of 94% and 90% respectively was achieved by the ML model.

Research on Driver's Seating Position Based on Chinese Human Characteristics

Research on Driver's Seating Position Based on Chinese Human Characteristics

Influence of occupant collision state parameters on the lumbar spinal injury during frontal crash

IntroductionDeveloped a detailed finite element model of spine and validated with the experimental or cadaveric tests to gain insight on occupant safety. ObjectivesThis study evaluates the influence of occupant collision state parameters such as height of the drop, occupant seating posture (occupant posture angle) and mass of the upper body on the risk of lumbar spinal injury during a frontal crash. MethodsThis parametric evaluation utilizing response surface methodology (RSM) performed. ANOVA was used to test the significance of parameters. ResultsHigher axial force of 3547 N is observed with higher dropping distance of 1500 mm. Similarly, higher strain and energy absorption were observed for the same dropping condition respectively. ConclusionThe result shows that all the factors considered in the experiment contribute to the risk of spinal lumbar injury during the frontal crash. Among all, height of the drop and the occupant posture angle are the most significant parameters in determining the lumbar spinal injury of occupant. It is observed that the injury criteria are directly proportional to the posture angle of the seat and height of drop.

Relationship between seat surface shape and pressure distribution in school seat models.

Students remain in a sedentary position inside classrooms for 60% to 80% of their school day. As such, research has associated students' prolonged seated posture on school furniture with their discomfort and musculoskeletal pain. The correlation between the shape of the seat surface and the zones of the body making contact with these surfaces constitutes an essential factor in determining comfort-enhancing seat design. This study's primary aim lies in contrasting the standard, current school chair against two seat prototypes, both designed and built from digital models, comparing seat-user pressure distribution and contact area during students' performance of different school tasks. Participants (n = 13), ages 7 to 19, performed school tasks sitting on three different chairs' seat surfaces during the test: the current seat used in schools and two seat prototypes, each designed based on body anatomy. The seats were evaluated through a force-sensing array pressure-mapping system. The measurements from designed seat prototypes provide a better distribution of pressures and greater contact area with the students' anatomical areas (buttocks and thighs) than the seat currently used in the specified schools. The improvement in pressure values and contact area as seen in the second designed seat prototype is due to its inclination angle and contact with students' sacral zone. This research work found that a seat's shape based on human anatomical features (buttocks and thighs), compared to a completely flat seat, creates a higher reduction of body pressures and an increase in the body contact area, with the intent to increase comfort and reduce musculoskeletal pain.

Difference Thresholds for the Perception of Sinusoidal Vertical Stimuli of Whole-Body Vibrations in Ranges of Amplitude and Frequency Relevant to Ride Comfort

Minor differences in the vibration characteristics of a vehicle may greatly influence the comfort experienced by the driver. Therefore, such characteristics are significant in the process of vehicle development. In this experimental study, just-noticeable differences were determined for sinusoidal vertical whole-body vibrations at the frequencies 1.3 Hz and 6.0 Hz, and for the vibration amplitudes 0.2 m/s², 0.5 m/s² and 1.2 m/s². The stimulation set up was realised using a test rig constituting a seating position similar to that in a real vehicle environment. A transformed one-up-three-down method, in conjunction with a two-interval forced choice procedure, was used to determine difference thresholds, in accordance with Weber’s Law, for 14 test subjects. Median relative difference thresholds in the range of 6.7% to 11.0% were observed, and were examined for statistical significance (α &lt; 0.05) and practical importance on amplitude and frequency, with respect to this law. The results showed a frequency-dependence at the lowest vibration amplitude and an amplitude-dependence for both frequencies from a statistical point of view. However, the amplitude-dependence at 6.0 Hz was considered as negligible for practical use.

Seated postural loads caused by shock-type whole-body vibration when driving over obstacles

ABSTRACT Operators of mobile machines within forestry work long hours in seated postures while being exposed to whole-body vibration (WBV) that is associated with pain in the lower back and neck. Still, little is known about the contribution from postural loads. In this study postural loads and shock-type WBV exposure on drivers operating a forwarder during terrain-like conditions was measured and quantified using inertial measurement units (IMUs). Five male drivers drove a forwarder repeatedly over standardized steel obstacles using a predefined speed and posture followed by driving over natural obstacles along a terrain course using a self-selected speed and posture. IMUs were affixed along the spine, on the back of the head of the driver and on the seat to detect orientation, velocity, and acceleration. The result shows that the methodology for measuring WBV and postural load with IMUs is feasible. Postural loads, expressed as range of motions (ROMs), when driving over a single standardized obstacle at a speed of 3.3 km/h were up to 21° in the neck segments. Increasing vehicle speed and size of obstacles increased postural loads. The terrain course resulted in higher ROMs in all body segments compared to a standardized obstacle, a difference in sideway seat acceleration but no differences regarding angular velocities of the head. Mechanical shocks at the seat were prevalent but the action limit value was exceeded only for one driver. Postural loads remained small during all conditions indicating that the spine can remain stable during exposure to shock-type WBV of this nature.

Positioning human body models for crashworthiness using model order reduction

A new technique to accelerate the positioning of human body models (HBMs) by means of a dimensionality reduction of a database of precomputed simulations is presented. First, a set of important subspace deformation modes which are used to approximate the model’s movements observed in the training simulations are computed. In the second step, a convex optimization problem is solved in order to obtain an optimal position of the human body model as described by the user. We apply the proposed method to a new reclined seating position of the Total Human Model for Safety (THUMS, v5).

DESIGNING AN EXPERIMENT FOR EVALUATING SEATING POSITIONS IN PARALYMPIC ROWING

AbstractWhen designing high performance sports equipment for Paralympic athletes, there are many unknowns for the design engineer to consider. The design challenge is an optimisation task per individual athlete. However, modelling this optimisation is difficult due to the many variables. This article presents the design of an experiment for identifying and evaluating various seating positions in Paralympic rowing by using a rowing ergometer with a modified seat. Results indicate that changing seating position has a substantial impact on per-athlete rowing performance.

Effect of sitting posture on pelvic injury risk under vertical loading

Underbody blast (UBB) attacks on military vehicles can result in severe pelvic injuries to the vehicle occupants. The aim of this study was to evaluate the biomechanical responses of the pelvis to UBB-like vertical loading in different seated postures. High-rate axial loading were performed on six defleshed human cadaveric pelves, whilst a three-dimensional finite element model of a human pelvis was created and used to simulate the high-rate loading with the model responses validated against experimental measurements. Three pelvic orientation corresponding to normal, upright, and relaxed seated postures, along with three different sacral slope angles representing the range of relative pelvis and sacrum positions known to exist across the population, were studied. The results showed that a decrease in posterior pelvic tilt slightly reduced the severity of sacral fracture, while an increase in sacral angle extended the region of anterior sacral fracture but reduced the extent to which the dorsal sacrum fractured. Across all seated postures, the predicted fractures of the ischial tuberosity, ischium, pubic rami and sacrum coincided with the typical pelvic fracture patterns observed in UBB events. The present study suggests that adopting an upright initial seated posture prior to an UBB event may reduce the risk of pelvic injuries.

Innovative Active Head Restraint System in a Car: Safety Assessment with Virtual Human Body Model

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;The aim of this study is to use numerical simulations for safety assessment of an innovative active head restraint system. This system was developed to protect the head and neck of an occupant in a car without a head airbag during a side impact. Its FE model is created and embedded it in a model of a small car with a side airbag. The dynamics of the head restraint activation are also taken into account. The virtual human body model Virthuman is used to represent occupants. The model is scaled for pre-selected human individuals to cover large numbers of occupants of different sizes. It extends conventional virtual evaluation of new safety designs via existing pre-defined mono-purpose side dummies and their FE models. The benefit of the head restraint system is evaluated in side impact scenarios inspired by the pole tests performed by EuroNCAP. Transversal impacts to a pole at 29 and 32 km/h are considered at 90° and 75° angles from driver and the opposite side. Also, the far side impact prescribed with an acceleration pulse according to EuroNCAP is considered. Various initial driver sizes in standard seated positions are tested. To extend the study beyond standard testing protocols, out-of-position of driver is also considered, leading to more than 100 simulations of impact scenarios in total. The effect of the innovative head restraint system is assessed from the point of view of driver injury risk.&lt;/div&gt;&lt;/div&gt;

New insights into lumbar flexion tests based on inverse and direct kinematic musculoskeletal modeling

Measurement of maximal lumbar flexion is considered to be a crucial element in the assessment of lumbar spine mechanics in situations as diverse as physiotherapy, orthopaedics, ergonomics, sport or aging. However, currently, there is no consensus on a reference test.This study aims to characterise five maximal lumbar flexion tests (four classical tests and a new, specifically-developed test designed to constrain pelvic retroversion) based on a three-dimensional, participant-specific musculoskeletal model.Twenty-six male and female participants performed the five tests. Movements were modelled in OpenSim to estimate change in length in lumbar, hamstring and gluteus muscles, together with lumbar flexion and pelvic tilt. These so-called “inverse” kinematic results were compared using a two-way ANOVA (sex×test). In a second step, lumbar muscle change in length was computed using a direct kinematic method.Lumbar flexion and lumbar muscle change in length were found to be greater when participants were in seated postures, with little pelvic retroversion. Female participants were observed to have less lumbar flexion than male participants (77±14° and 91±12°, respectively). Hip extensor muscles (hamstrings and gluteus) were fully stretched during each of the five tests. Our results highlight the specific roles of hamstrings, gluteus and lumbar muscles into reaching maximal lumbar flexion.Coupling inverse and direct kinematic methods proved to be a useful tool to enhance our knowledge of lumbar tests. Our findings help to characterise the role of the muscles involved in lumbar flexion, and we propose some recommendations for improving and standardising these tests.

Predictive Forward Dynamic Simulation of Manual Wheelchair Propulsion on a Rolling Dynamometer.

Research studies to understand the biomechanics of manual wheelchair propulsion often incorporate experimental data and mathematical models. This project aimed to advance this field of study by developing a two-dimensional (2D) model to generate first of its kind forward dynamic fully predictive computer simulations of a wheelchair basketball athlete on a stationary ergometer. Subject-specific parameters and torque generator functions were implemented in the model from dual X-ray absorptiometry and human dynamometer measurements. A direct collocation optimization method was used in a wheelchair propulsion model for the first time to replicate the human muscle recruitment strategy. Simulations were generated for varying time constraints and seat positions. Similar magnitudes of kinematic and kinetic data were observed between simulation and experimental data of a first push. Furthermore, seat heights inferior to the neutral position were found to produce similar joint torques to those reported in previous studies. An anterior seat placement produced the quickest push time with the least amount of shoulder torque required. The work completed in this project demonstrates that fully predictive simulations of wheelchair propulsion have the potential of varying simulation parameters to draw meaningful conclusions.

Kinematic and Biomechanical Response of Post-Mortem Human Subjects Under Various Pre-Impact Postures to High-Rate Vertical Loading Conditions.

Limited data exist on the injury tolerance and biomechanical response of humans to high-rate, under-body blast (UBB) loading conditions that are commonly seen in current military operations, and there are no data examining the influence of occupant posture on response. Additionally, no anthropomorphic test device (ATD) currently exists that can properly assess the response of humans to high-rate UBB loading. Therefore, the purpose of this research was to examine the response of post-mortem human surrogates (PMHS) in various seated postures to high-rate, vertical loading representative of those conditions seen in theater. In total, six PMHS tests were conducted using loading pulses applied directly to the pelvis and feet of the PMHS: three in an acute posture (foot, knee, and pelvis angles of 75°, 75°, and 36°, respectively), and three in an obtuse posture (15° reclined torso, and foot, knee, and pelvis angles of 105°, 105°, and 49.5°, respectively). Tests were conducted with a seat velocity pulse that peaked at ~4 m/s with a 30-40 ms time to peak velocity (TTP) and a floor velocity that peaked at 6.9-8.0 m/s (2-2.75 ms TTP). Posture condition had no influence on skeletal injuries sustained, but did result in altered leg kinematics, with leg entrapment under the seat occurring in the acute posture, and significant forward leg rotations occurring in the obtuse posture. These data will be used to validate a prototype ATD meant for use in high-rate UBB loading scenarios.

Basal and post-exercise heart rate variability correlates with training load in endurance athletes

Objective: Heart rate variability has been proposed as a valid method to examine the individual response to training load in endurance athletes. Thanks to this tool, the relationship between basal and post-exercise Heart rate variability measurements can be analyzed during a microcycle (one week) using straight values or their coefficients of variation.&#x0D; Method: Ten amateur endurance athletes (n = 5 men, n = 5 women) were monitored during a 7-day microcycle that included three road-cycling sessions, two running sessions and two trail-running sessions. The RR series were measured for 5 minutes upon wake up and after training, in a seating position, using a chest strap.&#x0D; Results: Basal and post-exercise Heart rate variability measurements showed high correlation when weekly mean values were used, very similar to when coefficients of variation values were used. In women, the root mean square of successive differences (RMSSD) was: r= 0.73; RMSSD coefficients of variation (RMSSDcv) was: r= 0.66; natural logarithm (Ln) RMSSD: r= 0.68; LnRMSSDcv: r= 0.79; and in men it RMSSD was: r= 0.78; RMSSDcv: r= -0.62; LnRMSSD: r= 0.75; LnRMSSDcv: r= -0.73).&#x0D; Conclusion: the relationship between these two measurements could be useful to program the training loads of the following microcycle.

Ultrasound assessment of diaphragm function in patients with late-onset Pompe disease.

Late-Onset Pompe Disease (LOPD) is characterized by progressive limb-girdle muscle weakness and respiratory dysfunction. Diaphragm is the most impaired muscle in LOPD and its dysfunction cause major respiratory symptoms. The aim of this study was to evaluate the correlation between diaphragm thickness and mobility assessed by ultrasonography and respiratory function and muscle strength tests in patients with LOPD. 17 patients with LOPD (9 female, 47 ± 15years) and 17 age and gender-matched healthy controls underwent spirometry, muscle strength testing, and ultrasound evaluation of diaphragm excursion and thickness. The following parameters were significantly reduced in LOPD patients versus controls (all p < 0.001): forced vital capacity (FVC) in seated and supine position, maximum inspiratory and expiratory pressure (MIP and MEP), diaphragm excursion, thickness at functional residual capacity (FRC) and total lung capacity (TLC), and thickness fraction (TF). Ultrasound studies of diaphragm thickness at FRC correlated with MIP (r = 0.74; p < 0.0001) and seated FVC(r = 0.73; p < 0.05). Diaphragm thickness at TLC correlated with MIP (r = 0.85; p < 0.0001) and FVC in both seated (r = 0.77; p < 0.0001) and supine position (r = 0.68; p < 0.05). TF correlated significantly with MIP (r = 0.80; p < 0.001), FVC in both seated (r = 0.66; p < 0,005) and supine position (r = 0.61; p < 0.05). Interestingly diaphragm thickness at FRC correlated with disease duration (years) in LOPD patients (r = -0.53; p < 0,05). Ultrasound diaphragm mobility correlated with diaphragm thickness at TLC(r = 0.87; p < 0.0001), FRC (r = 0.84; p < 0.005) and TF (r = 0.73; p < 0.05). Moreover diaphragm mobility correlated with FVC in seated(r = 0.79; p < 0.005) and supine position(r = 0.74; p< 0.05) and MIP (r = 0.81; p < 0.005). Diaphragm ultrasonography is a simple and reproducible technique for manage respiratory dysfunction in LOPD patients.

학습자의 성취도와 좌석선호도를 고려한 강의실 환경 및 교육시설 배치 연구

학습자의 성취도와 좌석선호도를 고려한 강의실 환경 및 교육시설 배치 연구