Seat Position Research Articles

Acute effects of an exercise based multimodal in-patient rehabilitation protocol in male knee osteoarthritis patients and the two years follow-up sustainability.

Working with lifting and carrying heavy loads and kneeling postures with crawling, squats or heel seat position lead to progressive cartilage wear with premature degenerative changes. To investigate the effects of the exercise based multimodal 'knee college' and its sustainability in patients with knee osteoarthritis with data assessments before and after a starter course, before a 1-year and a 2-year follow-up refresher course in a retrospective observational study. A sample of 401 male patients (ICD10: M17 [arthrosis of knee]/ICF: s75011 [knee joint]) from the construction industries were assessed with Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), EuroQol (EQ-5D), Performance Assessment Capacity Testing (PACT), Isokinetic torque H/Q ratio and Physical Work Capacity Test (PWC). Retrospectively, after two years they were divided into three groups based on their intermediate sporting activity: gym (n = 194, age: 50.8±7.0, BMI: 28.8±4,3), home training (n = 110, age: 50.2±7.0, BMI: 28.4±4,2), no exercising (n = 97, age: 48.2±7.0, BMI: 29.2±4,6). Patients did not differ significantly in their demographic and anthropometric data prior to the rehab program. Significant interaction effects indicated group-dependent differing sustainability effects for the 2-year follow-up (all outcomes: p < 0.001, except for H/Q ratio: p = 0.03). Group-wise analyses revealed significant acute improvements (after 3-week in-patient starter rehab program: p < 0.05) for all groups in almost all outcomes (except the 'no sport' group, H/Q ratio p = 0.08). These effects remained significant (p < 0.001) only for the 'gym' group during the 1-year and 2-year follow-up. Our data indicate that 2-year sustainability of acute rehabilitation starter effects was demonstrated especially for patients with adherence and compliance to long-term gym based exercises.

Timing Differences in Stride Cycle Phases in Retired Racehorses Ridden in Rising and Two-Point Seat Positions at Trot on Turf, Artificial and Tarmac Surfaces.

Injuries to racehorses and their jockeys are not limited to the racetrack and high-speed work. To optimise racehorse-jockey dyads' health, well-being, and safety, it is important to understand their kinematics under the various exercise conditions they are exposed to. This includes trot work on roads, turf and artificial surfaces when accessing gallop tracks and warming up. This study quantified the forelimb hoof kinematics of racehorses trotting over tarmac, turf and artificial surfaces as their jockey adopted rising and two-point seat positions. A convenience sample of six horses was recruited from the British Racing School, Newmarket, and the horses were all ridden by the same jockey. Inertial measurement units (HoofBeat) were secured to the forelimb hooves of the horses and enabled landing, mid-stance, breakover, swing and stride durations, plus stride length, to be quantified via an in-built algorithm. Data were collected at a frequency of 1140 Hz. Linear Mixed Models were used to test for significant differences in the timing of these stride phases and stride length amongst the different surface and jockey positions. Speed was included as a covariate. Significance was set at p < 0.05. Hoof landing and mid-stance durations were negatively correlated, with approximately a 0.5 ms decrease in mid-stance duration for every 1 ms increase in landing duration (r2 = 0.5, p < 0.001). Hoof landing duration was significantly affected by surface (p < 0.001) and an interaction between jockey position and surface (p = 0.035). Landing duration was approximately 4.4 times shorter on tarmac compared to grass and artificial surfaces. Mid-stance duration was significantly affected by jockey position (p < 0.001) and surface (p = 0.001), speed (p < 0.001) and jockey position*speed (p < 0.001). Mean values for mid-stance increased by 13 ms with the jockey in the two-point seat position, and mid-stance was 19 ms longer on the tarmac than on the artificial surface. There was no significant difference in the breakover duration amongst surfaces or jockey positions (p ≥ 0.076) for the ridden dataset. However, the mean breakover duration on tarmac in the presence of a rider decreased by 21 ms compared to the in-hand dataset. Swing was significantly affected by surface (p = 0.039) and speed (p = 0.001), with a mean swing phase 20 ms longer on turf than on the artificial surface. Total stride duration was affected by surface only (p = 0.011). Tarmac was associated with a mean stride time that was significantly reduced, by 49 ms, compared to the turf, and this effect may be related to the shorter landing times on turf. Mean stride length was 14 cm shorter on tarmac than on grass, and stride length showed a strong positive correlation with speed, with a 71 cm increase in stride length for every 1 m s-1 increase in speed (r2 = 0.8, p < 0.001). In summary, this study demonstrated that the durations of the different stride cycle phases and stride length can be sensitive to surface type and jockey riding position. Further work is required to establish links between altered stride time variables and the risk of musculoskeletal injury.

Neck muscle activation in response to eye movement depends on sitting posture and is modified in whiplash associated disorders: Cross-sectional study

BackgroundActivity of specific neck muscles is modulated by eye movement. This activity modulation is exaggerated in people with whiplash associated disorders (WAD), but it is unknown whether it is impacted by sitting posture. ObjectiveThis study investigated; (i) whether activity of cervical muscles differs with spinal posture; (ii) whether the effect of eye gaze direction (horizontal/vertical) on neck muscle activity differs between postures, and (iii) whether these effects differ between individuals with and without WAD. MethodsIn three seated postures (normal relaxed, head forward, sit tall) electromyography (EMG) was recorded right obliquus capitis inferior (OI), multifidus (MF), splenius capitis (SP) and left sternocleidomastoid (SCM) with fine-wire and surface electrodes in ten healthy controls and nine with WAD. Electro-oculography recorded eye movements. ResultsIn controls, EMG was less for extensor muscles in Sit Tall than Head Forward, but higher in SCM. Only SC EMG modulated with eye movement. When WAD participants adopted similar sitting postures several responses were different; compared to Normal Relaxed posture OI EMG was less in Head Forward; MF EMG was less in Sit Tall; and SC was less in Head Forward and Sit Tall. Neck muscles in WAD were generally more sensitive to eye movement, except SC which did not modulate. ConclusionsThese finding support the hypothesis that neck muscle activity is influenced by spinal posture and eye movement. In WAD, this relationship is distorted and the response to eye movement is increased. SignificanceThese observations have potential implications for clinical management of individuals with WAD.

In-silico modelling of multi-strike insertion and torsional resistance of tapered revision hip stems: Insight into spline design philosophy.

Despite the clinical success of tapered splined titanium stems, a knowledge gap still exists between spline design and its primary mechanical stability, which is critical to the long-term success of revision hip arthroplasty. Additionally, almost all published pre-clinical studies relied on resource-intensive benchtop and cadaveric testing. Hence, the present study developed a novel computational model to investigate effects of spline geometry and configuration on axial and torsional stability of tapered stem. Dynamic explicit Finite Element Analysis coupled with a state-of-the-art adaptive meshing technique was used to simulate the highly non-linear contacts and large bony material deformations. Hybridising primary straight splines with secondary angled splines results in 41% and 10% increases of peak insertion force and post-seating moment than the predicate device for the same seating position. The primary straight splines cut at multiple circumferential bony locations, enhancing torsional stability; while the alternatively placed secondary angled splines form wedges with the bone, providing reliable seating and additional torsional resistance. To the best knowledge of the author, this is the first in-silico investigation of its kind to simulate multi-strike seating and torsional resistance of revision hip stems, offering an effective and efficient platform for future multi-factorial parametric study and uncertainty quantification.

Prevalence and Risk Factors of Musculoskeletal Disorders Among Police Employees: A Survey Study

Background: Musculoskeletal disorders are a widespread and increasing occupational health problems worldwide. The disorders that result from work related event are known as “work related musculoskeletal disorders” where workers experience discomfort in one or multiple body parts, pain in joints, tingling and swelling. MSDs are reported to significantly impact on quality of life, cause lost work time, increase work restriction, or disability. The police have high possibility of showing musculoskeletal pains due to rough physical activities, including duties, traffic control, driving, security, sports and drills, and handling heavy equipment, and are highly hospitalized or treated. Aim and Objectives: To determine the prevalence and risk factors of Musculoskeletal disorders in Police Employees. Methodology: The study was conducted among 100 police employees. The data was collected using Self - Administered Questionnaire, Nordic Musculoskeletal Questionnaire and Operational Police Stress Questionnaire. Result and conclusion: The 12-month prevalence of musculoskeletal disorders among police employees was 72%. Neck pain (51%) was found to be most prevalent followed by lower back (45%). The occurrence of Musculoskeletal Disorders was associated with factors such as age, work experience, longer working hours per day, daily alcohol consumption, and prolonged seated posture. Additionally, the study identified various operational stressors among police employees, including shift work, working alone at night, high overtime demands, fatigue, and unhealthy eating habits at work. Thus, strategies should be implemented to manage shifts, provide support and resources, promote healthy lifestyles, and mitigate fatigue, ultimately fostering a healthier and more resilient workforce that benefits both individual officers and overall law enforcement effectiveness. Keywords: Prevalence, Musculoskeletal Disorders, Risk Factors, Police Employees.

Relationship between Total Flight Hours and Individual Factors with Low Back Pain in Indonesian Military Helicopter Pilots

Introduction: Helicopter pilots are potentially at risk of Low Back Pain (LBP) and are twice as likely as fighter pilots to experience it. Helicopter pilots’ LBP is caused by a combination of risk factors: engine and rotor vibration, ergonomic risks due to cockpit design, static seating position due to operations, and individual factors. These factors are incorporated into cumulative aviation risk exposure, which can be measured by total flight hours. The prevalence of LBP in Caucasians is high, at 50.5%-92%. However, there has not been any research on Indonesian military helicopter pilots who have a different posture from Caucasians.Objective: To determine the prevalence of LBP, to analyze the relationship between total flight hours and individual factors (age, height, BMI, exercise habits, and smoking habits) with LBP in Indonesian military helicopter pilots.Methods: The study was conducted at the Indonesian Army and Indonesian Air Force with total sampling method as many as 124 people. An explanation was carried out followed by filling in the consent to become a research subject, filling in personal data, anamnesis, Numeric Rating Scale (NRS), physical examination, neurological examination, and total flight hour data.Results: There were 124 subjects, consisting of 37.9% pilots and 62.1% copilots, 87.9% of pilots operate large helicopters, have average total flight hours of 450 hours, age of 30 years, the height of 172.66 cm, low intensity exercise habits of 61.3%, and smokers as much as 45.2%. A total of 57 people (46%) experienced LBP. Statistical results showed that total flight hours had an association with LBP (p = 0.035) where each 1 unit increase in total flight hours had a 1.02 times greater chance of LBP.Conclusion: The prevalence of LBP is 46% and there is an association between total flying hours and LBP in Indonesian military helicopter pilots.

Child occupant safety in unconventional seating for vehicles with automated driving systems

The objective of this study was to use computational models to study how unconventional seating positions and orientations in vehicles with Automated Driving System (ADS) may affect occupant response metrics of children with various restraint conditions.A literature review was first conducted to frame a simulation plan, including selections of surrogate ADS-equipped vehicles, potential seating arrangements, impact scenarios, anthropomorphic test device (ATD) models, and child restraint system (CRS) models that are relevant to the selected ATD models. Due to the lack of impact tests with child ATDs and CRS in farside, oblique, and rear impacts, 17 sled tests were conducted with CRS harness-restrained ATDs and vehicle belt-restrained ATDs in frontal, farside, oblique, and rear impact conditions. The sled tests were then used to validate a set of MADYMO (MAthematical DYnamic MOdels) v7.7 models. A total of 550 simulations were then conducted with four child ATDs and various CRS conditions across a range of conventional and unconventional seating locations and orientations under five impact directions. We did not find major safety concerns with ATDs restrained by harnessed CRSs based on the nature of ATD contacts. Compared with frontal and rear impacts, CRSs may rotate laterally in farside and oblique impacts, which could result in higher head and chest injury measures than frontal due to inertial loading to the CRS, and the larger lateral rotation of the CRS may lead to a contact between the CRS and vehicle interior. The major safety concern for vehicle belt-restrained ATDs (with and without booster) is that they have the potential to contact the seat next to them or the instrument panel behind them in a farside or oblique impact. Unconventional seating does not necessarily create additional safety concerns beyond what we know with the conventional seating. However, due to the orientation of the unconventional seats, the occupants on those seats may be involved in a higher percentage of oblique and rear-oblique impacts relative to their seating orientations than conventional seats, which may be considered in the future safety design process.This is the first study using different child ATDs and CRSs to investigate child occupant responses in a wide range of impact directions and seating orientations. Results from the sled tests and simulations provide a better understanding of child occupant responses in those crash conditions, but also identified several limitations of using frontal ATDs in other crash directions.

THOR-05F biofidelity evaluation in reclined and upright seated postures subjected to frontal crash pulses

The THOR 5th percentile female dummy (THOR-05F) was evaluated for two seating postures/positions in frontal impacts using a generic automotive seat environment. The conditions included 2 crash pulses: a 15 km/h test that utilized 4.5 g acceleration and a 3-point restraint with 2 kN load limiter, and a 32 km/h test that utilized 9.5 g acceleration and a 3-point restraint with a 4.5 kN load limiter and pretensioner, and two seatback angles: 25°, a nominal upright posture, and 45°, a moderate reclined posture. The BRS scores were calculated using the NHTSA BioRank method. Overall biofidelity rating was consider excellent for both seating postures. This evaluation provides an understanding of the THOR-05F response and biofidelity evaluation of the ATD in two seating postures (nominal and reclined). This is essential in the assessment and development of safety measures in emerging ADS-equipped vehicles.

Early Rehabilitation with Exergame Which Muscle Groups are Addressed by Bedside-Based Knee Exercises?

Background. Knee exercises are generally recommended following knee-related operations. Nevertheless, compliance in performing self-administered exercises is varying. The use of exergames may alter patient compliance. These computer games encourage the user to exercise. Exergames are not yet used much in orthopedic rehabilitation. The aim of this study was to analyze the influence of different seating positions in electromyography while performing knee exercises with the exergame GenuSport.Material and methods. 72 healthy women and men were tested in 6 seating positions using an application-based knee-training device (KT). Positions were 1. user seated 90 upright with straight leg on KT, 2. 90 upright with leg exercising in external rotation on KT, 3. 90 upright with leg exercising in internal rotation on KT, 4. 90 upright with straight leg on 30mm elevated KT, 5. 45 upright with straight leg on KT and 6. 45 upright with straight leg on 30mm elevated KT. Electromyogram was recorded for biceps femoris, rectus femoris, semitendinosus, vastus medialis, adductor magnus and vastus lateralis.Results. No significant difference was shown in position 2, 3 or 4 compared to position 1. In position 5 and 6, EMG reported significantly higher values compared to positions 1 to 4 (ischiocrural: 130% and quadriceps: 90%). The quadriceps was activated significantly less in position 6 compared to 5.Conclusion. 1. Bedside-based knee extension exercises are most effective in a seated position of 45 trunk inclination. 2. A slightly more bent knee (KT elevation of 30mm) leads to a higher activation of the ischiocrural muscles.

Obese Occupant Response in Reclined and Upright Seated Postures in Frontal Impacts.

The American population is getting heavier and automated vehicles will accommodate unconventional postures. While studies replicating mid-size and upright fore-aft seated occupants are numerous, experiments with post-mortem human subjects (PMHS) with obese and reclined occupants are sparse. The objective of this study was to compare the kinematics of the head-neck, torso and pelvis, and document injuries and injury patterns in frontal impacts. Six PMHS with a mean body mass index of 38.2 ± 5.3 kg/m2 were equally divided between upright and reclined groups (seatback: 23°, 45°), restrained by a three-point integrated belt, positioned on a semi-rigid seat, and exposed to low and moderate velocities (15, 32 km/h). Data included belt loads, spinal accelerations, kinematics, and injuries from x-rays, computed tomography, and necropsy. At 15 km/h speed, no significant difference in the occupant kinematics and evidence of orthopedic failure was observed. At 32 km/h speed, the primary difference between the cohorts was significantly larger Z displacements in the reclined occupant at the head (190 ± 32 mm, vs. 105 ± 33 mm p < 0.05) and femur (52 ± 18 mm vs. 30 ± 10 mm, p < 0.05). All the moderate-speed tests produced at least one thorax injury. Rib fractures were scattered around the circumference of the rib-cage in the upright, while they were primarily concentrated on the anterior aspect of the rib-cage in two reclined specimens. Although MAIS was the same in both groups, the reclined specimens had more bi-cortical rib fractures, suggesting the potential for pneumothorax. While not statistical, these results suggest enhanced injuries with reclined obese occupants. These results could serve as a data set for validating the response of restrained obese anthropometric test device (ATDs) and computational human body models.

Calibration of head mounted displays for vision research with virtual reality.

Immersion in virtual environments is an important analog for scientists. Situations that cannot be safely organized in the real world are being simulated virtually to observe, evaluate, and train aspects of human behavior for psychology, therapy, and assessment. However, creating an immersive environment using traditional graphics practices may create conflict with a researcher's goal of evaluating user response to well-defined visual stimuli. Standard computer monitors may display color-accurate stimuli, but it is generally viewed from a seating position, where the participant can see real-world visual context. In this article, we propose a novel means to allow vision scientists to exert finer control over the participants visual stimuli and context. We propose and verify a device-agnostic approach to color calibration by analyzing display properties such as luminance, spectral distribution, and chromaticity. We evaluated five different head-mounted displays from different manufacturers and showed how our approach produces conforming visual outputs.

Sagittal Spinal Alignment in People with Chronic Spinal Cord Injury and Normal Individual: A Comparison Study Using 3D Ultrasound Imaging.

The aim of this study was to compare the sagittal spinal alignment of people with chronic spinal cord injury (SCI) with normal individuals and to determine whether transcutaneous electrical spinal cord stimulation (TSCS) could cause a change in the thoracic kyphosis (TK) and lumbar lordosis (LL) to re-establish normal sagittal spinal alignment. A case series study was conducted, wherein twelve individuals with SCI and ten neurologically intact subjects were scanned using 3D ultrasonography. In addition, three people with SCI having complete tetraplegia participated further to receive a 12-week treatment (TSCS with task-specific rehabilitation) after evaluation of sagittal spinal profile. Pre- and post-assessments were conducted to evaluate the differences in sagittal spinal alignment. The results showed that the TK and LL values for a person with SCI in a dependent seated posture were greater than those of normal subjects for: standing (by TK: 6.8° ± 1.6°; LL: 21.2° ± 1.9°), sitting straight (by TK: 10.0° ± 4.0°; LL: 1.7° ± 2.6°), and relaxed sitting (by TK: 3.9° ± 0.3°; LL: 7.7° ± 1.4°), respectively, indicating an increased risk for spinal deformity. In addition, TK decreased by 10.3° ± 2.3° after the TSCS treatment, showing a reversible change. These results suggest that the TSCS treatment could be used to restore normal sagittal spinal alignment for individuals with chronic SCI.

Is It Necessary to Obtain Lateral Pelvic Radiographs in Flexed Seated Position for Preoperative Total Hip Arthroplasty Planning?

Many of the current total hip arthroplasty (THA) planning tools only consider sagittal pelvic tilt in the standing and relaxed sitting positions. Considering that the risk of postoperative dislocation is higher when bending forward or in sit-to-stand move, sagittal pelvic tilt in the flexed seated position may be more relevant for preoperative planning. We hypothesized that there was a significant difference in sagittal pelvic tilt between the relaxed sitting and flexed seated positions as measured by the sacral slope in preoperative and postoperative full-body radiographs. This was a multicenter retrospective analysis of the preoperative and postoperative simultaneous biplanar full-body radiographs of 93 primary THA patients in standing, relaxed sitting, and flexed seated positions. The sagittal pelvic tilt was measured using the sacral slope relative to the horizontal line. The mean difference between the preoperative sacral slope in the relaxed sitting position and the flexed seated position was 11.3° (-13° to 43°) (P < .0001). This difference was >10° in 52 patients (56%) and >20° in 18 patients (19.4%). The mean difference between the postoperative sacral slope in a relaxed sitting position and the sacral slope in a flexed seated position was 11.3° (P < .0001). This difference was >10° in 51 patients (54.9%) and >30° in 14 patients (15.1%) postoperatively. There was a significant difference in sagittal pelvic tilt between the relaxed and flexed seated positions. A flexed seated view provides valuable information that might be more relevant for preoperative THA planning in order to prevent postoperative THA instability.

Discomfort estimation for vertical whole-body vibration in the aircraft cabin considering the duration and static sitting comfort

This paper investigated the discomfort caused by vertical whole-body vibration (WBV) over 20 minutes using data recorded at the front, middle, and rear seats of the passenger cabin in civil aviation during a cruising flight. Twenty-four subjects experienced each stimulus at 0.5 ms−2 r.m.s. and judged discomfort at various moments (i.e., 1/6, 5, 10, 15, and 20 min) using a category-ratio method. The difference in discomfort due to high-frequency vibration components vanished after 10 min. Based on Stevens’ power law, a method is developed to estimate long-term vertical WBV discomfort by considering the static discomfort and an interaction coefficient between vibration and static discomfort as parameters. The proposed estimation method showed high accuracy with determination coefficients (R 2) higher than 0.97 and good linearity with values of growth rates 0.95, 1 and 0.95 for the vertical WBV discomfort at the front, middle and rear seat positions in the aircraft cabin.

Effect of naturalistic seating postures and seatbelt routing on booster-seated Q6 ATD kinematics and kinetics in frontal impacts

Research questions / objectiveTest protocols evaluate restraint performance with pediatric ATDs placed in an ideal seating posture. However, real-world evidence suggests that ideal test conditions do not always reflect actual occupant positions. Prior studies have also shown that booster seat designs affect the position of the seatbelt around the child. Occupants in naturalistic seating postures, coupled with potentially unfavorable seatbelt positions, could result in adverse kinematics and kinetics in a crash. Therefore, the aim of this study was to quantify the effect of different naturalistic seating postures on the response of the Q6 ATD restrained on boosters with varying initial static belt fit in a frontal impact. Methods/data sourcesThe Q6 ATD was positioned on two booster seats of similar design but varying static belt fit metrics in three seating postures: reference, leaning forward, and leaning inboard. These booster seats were chosen from extensive belt fit studies on human volunteers and ATDs, and were defined as follows:•Booster A: more inboard shoulder belt position, more inferior lap belt position, larger gap size.•Booster B: more outboard shoulder belt position, more superior lap belt position, smaller gap size.The booster-seated ATD was restrained on the simulated Consumer Reports test buck (2010 Ford Flex 2nd row seat) with a front blocker plate using a 3-point lap-shoulder belt with a retractor and pretensioner. The sled environment was subjected to the FMVSS 213 frontal impact pulse, and each booster and seating posture was evaluated twice (n = 12 sled tests). Kinematic and kinetic measures were recorded. A linear regression analysis was conducted across postures on each booster. Further, a paired t-test analysis was conducted across booster seats for each seating posture. ResultsAcross seating postures, the reference posture exhibited similar or higher kinematic and kinetic metric values compared to the leaning forward and leaning inboard postures on both boosters. However, both leaning forward (Booster A = 279.5 ± 21.6 mm; Booster B = 298.8 ± 1.5 mm) and leaning inboard (Booster A = 308.7 ± 1.1 mm; Booster B = 331.4 ± 8.5 mm) postures generally resulted in greater head excursion than the reference posture (Booster A = 285.0 ± 16.9 mm; Booster B = 288.1 ± 1.5 mm), indicating greater potential for head contact.Between boosters, Booster A resulted in significantly lower head 3 ms clip acceleration (p = 0.0026), HIC15 (p = 0.0008), upper neck tensile force (Fz)(p = 0.0057), chest 3 ms clip acceleration (p = 0.0013), and right abdominal pressure (p = 0.0163), and significantly higher left ASIS force (Fx)(p = 0.0150) and left (p = 0.0489) and right (p = 0.0088) ASIS moment (My) than Booster B. Upper neck tensile forces on Booster B crossed the 20% and 50% thresholds for AIS3 + injury. Lower abdominal pressure and higher ASIS forces and moments on Booster A suggest that the lap belt loaded the ASIS appropriately, and hence, relatively better kinematics than Booster B. Significance of resultsThis study shows that booster design affects static belt fit which can have an effect on dynamic crash performance and assessment criteria. By connecting static belt fit to dynamic performance, these effects may have the potential to help guide booster seat design.

Improving old tricks as new: Young adults learn from repeating everyday activities.

The notion that young healthy adults can substantially improve in activities that are part of their daily routine is often overlooked because it is assumed that such activities have come to be fully mastered. We followed, in young healthy adults, the effects of repeated executions of the Timed-Up-and-Go (TUG) task, a clinical test that assesses the ability to execute motor activities relevant to daily function-rising from a seated position, walking, turning and returning to a seated position. The participants (N = 15) performed 18 consecutive trials of the TUG in one session, and were retested on the following day and a week later. The participants were video recorded and wore inertial measurement units. Task execution times improved robustly; performance was well fitted by a power function, with large gains at the beginning of the session and nearing plateau in later trials, as one would expect in the learning of a novel task. Moreover, these gains were well retained overnight and a week later, with further gains accruing in the subsequent test-sessions. Significant intra-session and inter-session changes occurred in step kinematics as well; some aspects underwent inter-sessions recalibrations, but other aspects showed delayed inter-session changes, suggesting post-practice memory consolidation processes. Even common everyday tasks can be improved upon by practice; a small number of consecutive task repetitions can trigger lasting gains in young healthy individuals performing highly practiced routine tasks. This new learning in highly familiar tasks proceeded in a time-course characteristic of the acquisition of novel 'how to' (procedural) knowledge.

Relative Safety Assessment for Positioning Children in Vehicles with Varying Levels of Advanced Safety Technologies

Recent studies suggest that advances in rear seat occupant protection are trailing while frontal crash prevention technologies have disproportionately improved front seat occupant safety. Therefore, the first objective of this study is to identify the safest seat for children by estimating injury severity by seat position using current crash data. The second objective of this study is to demonstrate that Level-2 and above (i.e., L2+) AVs will be significantly different from current vehicles regarding child injury severity, and therefore it is essential to find the safest seat for children in L2+ AVs. This study utilized data from the National Automotive Sampling System (NASS) to estimate crash injury severity by seat position in children. This study used the Injury Severity Score (ISS) as its measure of crash severity. The mean ISS for restrained children sitting in the front passenger seat was 0.494 (for model year &gt; 2000 vehicles). The mean ISSs for second-row left and second-row right seats were 0.374 and 0.322, respectively. The second-row middle seat had 162, 98, and 71% lower mean ISSs than the front passenger, second-row left, and second-row right seats, respectively. Overall, in both restrained and unrestrained scenarios, the safest seat for a child was the second-row middle seat.

An experimental investigation of active control of road noise employing the weighted error signal to maximize the noise suppression performance at focused control positions

This study presents the practical implementation and validation of an automotive active road noise control (ARNC) system that can concentrate control efforts on a selected position by employing a weighting factor in error microphone signals. The current ARNC system is designed to uniformly attenuate road noise across the entire seating position in the vehicle cabin, which results in the abandonment of the ability to maximize noise suppression performance in a single seat. It can be expected that the noise suppression performance of the selected position can be further improved by applying a weighting factor to the error signal to concentrate the control effort. However, practical demonstration of the implementation and evaluation of this approach in modern ARNC systems is scarce. To validate this approach, we investigated the influence of weighting factors in the error signals on the noise suppression performance. A practical active control system was implemented in a large luxury sedan, and the noise attenuation performance according to the weighting factor was evaluated based on real driving experiments. The experimental results show that relatively high weighting factors at the selected location can improve the noise attenuation performance. Moreover, it was found that a small weighting factor of 0.01 is suitable to prevent the acoustic amplification of uncontrolled error microphones, as opposed to the extreme condition where the weighting factor is 0.

Simulink-Based Simulation of Gas Pilot Servo Actuator for Aviation Ejection Seat

The ejection seat needs the ability of rapid attitude adjustment to save lives, and the gas servo steering engine is a feasible scheme for correcting the seat position. The three closed-loop control system of the permanent magnet synchronous motor is built to realize the rotor position loop control of the motor; the working principle of the gas steering gear is analyzed, and the mathematical model of the gas servo system is constructed; Simulink is used to simulate the position of the motor and gas valve; the simulation results show that the steering gear can respond quickly to the control command, and the torque to the rudder surface generated by gas is large enough to meet the needs of the rudder blade to overcome the torque generated by the erosion of the rudder surface and the timeliness of the ejection seat.

Application of data-driven surrogate models for active human model response prediction and restraint system optimization

Surrogate models are a must-have in a scenario-based safety simulation framework to design optimally integrated safety systems for new mobility solutions. The objective of this study is the development of surrogate models for active human model responses under consideration of multiple sampling strategies. A Gaussian process regression is chosen for predicting injury values based on the collision scenario, the occupant's seating position after a pre-crash movement and selected restraint system parameters. The trained models are validated and assessed for each sampling method and the best-performing surrogate model is selected for restraint system parameter optimization.