Body Seat Research Articles

Differences of Physical Condition between China National Level Social Sports Instructor and the Coeval

The objective of this paper is to focus on the differences of physical condition between China National Level Social Sports Instructor and the Coeval. Methods: Test the vital capacity, step test, reacting time, crook before the seat body, grip strength, eye-closed and single-legged standing. The results were compared between experimental group and control group. Results: compared with control group, cardio-respiratory function of experimental group was obviously better (P<0.05). The flexibility, static balance ability and the grip strength of experimental male were obviously better (P<0.05). The static balance ability of experimental female was very obviously better (P<0.01). But the flexibility and static balance ability of the experimental female didn’t have obviously discrepancy (P>0.05). The reacting time between the two groups didn’t have obviously discrepancy. Conclusion: The physical conditions of National Level Social Sports Instructor are obviously better than the coeval, which is the important factor to conduct the instruction process of social sports.

A Study on Mechanism of Wear of Nozzle Body Seat of Diesel Fuel Injector

A Study on Mechanism of Wear of Nozzle Body Seat of Diesel Fuel Injector

Feasibility of home-based functional electrical stimulation cycling: case report

Single-subject (male, 64 years of age) case. To determine the feasibility of a home-based FES-LEC (functional electrical stimulation lower extremities cycling) program and effects on body composition, quality of life (QOL) and seat pressure mapping in an older individual with spinal cord injured (SCI). Home-based FES-LEC with internet connection. Southeastern United States. FES-LEC three sessions per week for 9 weeks in the participant's home and monitored by the research staff via internet connection. Pre- and post-exercise program testing of seat pressure mapping, QOL and body composition including percent body fat (%BF), fat mass (FM), lean mass (LM) and bone mineral density (BMD). The participant completed 25 of 27 recommended exercise sessions over 9 weeks for a 93% compliance rate. Cycling distance increased from 3.98 to 9.00 km (126%). Total body LM increased from 48.94 to 53.02 kg (8.3%). The %BF decreased from 29.6 to 28.4(-1.2%). Total body weight, FM and BMD remained unchanged. Average static seat pressure decreased from 55.5 to 52.59 mm Hg (5%), whereas maximum seat pressure decreased from 120.76 to 91.5 mm Hg (24%). The psychological domain (perception of body image, appearance and self-esteem) of the QOL questionnaire improved from 12.67 to 14. Positive changes in this study regarding body composition, QOL and seat pressure mapping support results of clinical studies using FES-LEC training on younger adults with SCI. The high percentage of exercise adherence and positive results on body composition, QOL and seat pressure provide support for the feasibility of home-based FES-LEC.

Analysis and optimum design of rider-bicycle mechanisms: Design of bicycle parameters for a specified rider

Optimum design of rider-bicycle mechanisms is very important for customizing bicycles and plays a crucial role in the improvement of athletes’ performances and in protection of the riders. Since the birth of the first bicycle, people have been keeping optimizing bicycles with respect to physical conditions of human. In modern design, the basic structure of a bicycle has been formulized, while many geographic parameters remain uncertain. In this paper, the bicycle and the human body are considered as a kinematic mechanism, called rider-bicycle mechanism. The optimum design is implemented from the perspective of mechanism. Effort-saving and comfortableness are considered at the same time. The corresponding performance charts are drawn and the relationship between the performances and parameters of seat height, crank length and body parameters are discussed. By using these charts, the optimal design method of bicycle’s parameters for a specified person is then founded. Optimum solutions to get suitable seat height and crank length for a person are obtained accordingly. The research is of significance for customizing bicycles and design of bicycle robot.

Dynamic modeling of seated human body based on measurements of apparent inertia matrix for fore-and-aft/vertical/pitch motion

Various models of a seated human body have been developed in the literature so far based on measurements of apparent mass in the vertical Z-direction alone or fore-and-aft X-direction alone. As the authors observed that accelerations in both X and Z directions are equally significant in tests on an excavator working in a quarry, 3×3 apparent inertia matrix was experimentally obtained as functions of frequency by exciting the seated human body in the Z– X plane, i.e. providing two translational motions in the Z and X axes and one angular motion about the Y-axis. A subject in slightly slouched posture was sitting on a seat without backrest and the hands were on lap. Five resonances were found in the frequency range of interest, i.e. up to 20 Hz, below 1 Hz and at 3, 5.25, 8, 9.5 Hz, which is one more than four resonances found in previous researches. The resonance at 8 Hz was newly found in only pitch component of the apparent inertia matrix. Since the experiment was carried out only for one subject, it may not be guaranteed that the new resonance is generally applicable. A 5-degree-of-freedom (dof) model with 23 parameters is proposed for the description of the apparent inertia matrix of a seated human body. The 8 geometric parameters were included in the model in order to describe the couplings between coordinates. The model yielded the resonances at 0.61, 3.3, 5.1, 8.8 and 9.8 Hz, which are near to observations of the experiment. The parameters of the models may not necessarily represent the physical values of a human body because only the apparent inertia matrix at human body–seat interface was reflected. The model may not be perfect because the apparent inertia matrix was obtained from only one subject. Yet, the observations and the model in this research could be a guideline or reference in future researches to obtain more perfect models. Since the vibration responses in the Z– X plane at the human–seat interface can be predicted using the proposed 5-dof model, this model could be used for evaluation of a seat system by computer simulations from the aspect of ride comfort and health.

Failure Analysis of Kelly Cock Valve Used in Drilling Process

Though statistically analyzing ten typical wells of kelly cock valve failure in certain oilfields, the main failure modes of the kelly cock valve were determined. Aiming at these modes and combining with mechanical analysis of knob, upper seat and main body of the kelly cock valve, its finite element calculation had been implemented and the weakness of all parts was found. By numerical modeling of the flow field of a kelly cock valve it was found that the velocity of fluid rapidly increased at upper and lower valve seats and this could easily prick out ball valves and valve seats, there was a annular low-velocity zone of minimum speed between the ball valve and the inner wall of the main body and this caused solid aggregation at this area. The research in this paper made the modes and causes of kelly failure to be recognized systematically. The results provided theoretical foundations of further improving the design and reasonable using of a kelly cock valve.

The relationship between cadence, pedalling technique and gross efficiency in cycling.

Technique and energy saving are two variables often considered as important for performance in cycling and related to each other. Theoretically, excellent pedalling technique should give high gross efficiency (GE). The purpose of the present study was to examine the relationship between pedalling technique and GE. 10 well-trained cyclists were measured for GE, force effectiveness (FE) and dead centre size (DC) at a work rate corresponding to ~75% of VO2max during level and inclined cycling, seat adjusted forward and backward, at three different cadences around their own freely chosen cadence (FCC) on an ergometer. Within subjects, FE, DC and GE decreased as cadence increased (p < 0.001). A strong relationship between FE and GE was found, which was to great extent explained by FCC. The relationship between cadence and both FE and GE, within and between subjects, was very similar, irrespective of FCC. There was no difference between level and inclined cycling position. The seat adjustments did not affect FE, DC and GE or the relationship between them. Energy expenditure is strongly coupled to cadence, but force effectiveness, as a measure for pedalling technique, is not likely the cause of this relationship. FE, DC and GE are not affected by body orientation or seat adjustments, indicating that these parameters and the relationship between them are robust to coordinative challenges within a range of cadence, body orientation and seat position that is used in regular cycling.

Manufacturing and Structural Feasibility of Natural Fiber Reinforced Polymeric Structural Insulated Panels for Panelized Construction

Natural fibers are emerging in the fields of automobile and aerospace industries to replace the parts such as body panels, seats, and other parts subjected to higher bending strength. In the construction industries, they have the potential to replace the wood and oriented strand boards (OSB) laminates in the structural insulated panels (SIPs). They possess numerous advantages over traditional OSB SIPs such as being environmental friendly, recyclable, energy efficient, inherently flood resistant, and having higher strength and wind resistance. This paper mainly focuses on the manufacturing feasibility and structural characterization of natural fiber reinforced structural insulated panels (NSIPs) using natural fiber reinforced polymeric (NFRP) laminates as skin. To account for the use of natural fibers, the pretreatments are required on natural fibers prior to use in NFRP laminates, and, to address this issue properly, the natural fibers were given bleaching pretreatments. To this end, flexure test and low-velocity impact (LVI) tests were carried out on NSIPs in order to evaluate the response of NSIPs under sudden impact loading and uniform bending conditions typical of residential construction. The paper also includes a comparison of mechanical properties of NSIPs with OSB SIPs and G/PP SIPs. The results showed significant increase in the mechanical properties of resulting NSIP panels mainly a 53% increase in load-carrying capacity compared to OSB SIPs. The bending modulus of NSIPs is 190% higher than OSB SIPs and 70% weight reduction compared to OSB SIPs.

Vibrations control of light rail transportation vehicle via PID type fuzzy controller using parameters adaptive method

In this study, a conventional PID type fuzzy controller and parameter adaptive fuzzy controller are designed to control vibrations actively of a light rail transport vehicle which modeled as 6 degree-of-freedom system and compared performances of these two controllers. Rail vehicle model consists of a passenger seat and its suspension system, vehicle body, bogie, primary and secondary suspensions and wheels. The similarity between mathematical model and real system is shown by comparing uncontrolled simulation results and vibration measurements. For carrying a comfortable travel, rail vehicle body and passenger seat vibrations are minimized by adding a controller between rail vehicle body and bogie in the model of this system. To control vibrations actively, a PID type fuzzy controller which is obtained by combining fuzzy PI and fuzzy PD controllers is preferred because of its robust character and superior performance. The PID type fuzzy controller using parameter adaptive method is designed by tuning the parameters online. Also, obtaining higher performance from this controller is studied.

Modelling the fore-and-aft apparent mass of the human body and the transmissibility of seat backrests

A combined lumped-parameter and multi-body system dynamic model of the human body–seat system has been constructed with masses and moments of inertia and with linear translational and rotational springs and dampers. The model was developed in four steps by minimising the sum-of-least-squares error between laboratory measurements and model predictions of the fore-and-aft driving point apparent mass and the fore-and-aft transmissibility of a car backrest. Good agreement was achieved between model predictions and both the median measured driving-point apparent mass and the median measured backrest transmissibility with six subjects. The model was capable of representing the measured apparent masses and predicting the backrest transmissibility with the individual subjects. It was also capable of predicting the backrest transmissibilities of two different car seats. A sensitivity study was conducted and the effects of the model parameters on the peak moduli and corresponding frequencies of the apparent mass and the backrest transmissibility are presented.

A simplified 3-D human body–seat interaction model and its applications to the vibration isolation design of high-speed marine craft

High-speed boats experience a harsh vibration environment and human response to this environment is of increasing interest to naval architects who wish to mitigate the effects of vibration and shocks. Based on published experiment data, a three-dimensional human body model with one degree-of-freedom in each direction is established. This model is combined with a simple seat model to construct a simplified 3-D human body–seat interaction model for naval architects to investigate the integrated interaction system when subjected to ship motions. The governing equations describing the dynamics of the human body–seat interactions are formulated and their theoretical solutions are derived. This model, in association with the experimental data recorded on board a high-speed marine craft, is used to study seat isolation system designs. The spring coefficient of the seat isolation system is chosen to avoid any resonance of the human–seat interaction system excited by sea waves. The damping coefficient of the seat isolation system is determined to attenuate motions at the most common excitation frequencies. The designed system is further checked by considering its response to an individual slam impact where the designed system is compared with typical existing seats to illustrate the potential advantages of the proposed approach. In addition the designed seat is compared with existing seats excited by actual boat loads. The study provides a simplified, effective approach for high-speed craft seat design in reducing the shock and vibration level experienced by the crew.

Effect of Chair Design on Feed-Forward Postural Control in Sitting

The objective of this study was to determine if a forward-tilted seat and the resultant semi-kneeling body position associated with sitting on the Balans Multi Chair (BMC) affect postural control in sitting. Nine healthy subjects were seated on either the BMC or a regular (REG) chair with their arms extended. They were instructed to induce self-initiated body perturbations in four different directions by exerting brief pulses of force against a stationary frame positioned in front of them. Electromyographic (EMG) activities of trunk and leg muscles were recorded before and during the perturbations. The results show that sitting on both types of chairs was associated with anticipatory activation of trunk and upper leg muscles. In contrast, anticipatory activation of distal muscles was observed while sitting only on the REG chair and was absent while sitting on the BMC. The outcome of the study suggests that although the forward-tilting seat and semi-kneeling body position might help in preserving a normal lordosis, it is not associated with anticipatory activation of lower leg muscles, which might reduce the ability of an individual to counteract self-initiated body perturbations. These findings stress the important role of chair designs in the control of sitting posture.

Health Literacy and Health Risk Behaviors Among Older Adults

Limited health literacy is associated with poorer physical and mental health, although the causal pathways are not entirely clear. In this study, the association between health literacy and the prevalence of health risk behaviors was examined among older adults. A cross-sectional survey of 2923 new Medicare, managed-care enrollees was conducted in four U.S. metropolitan areas (Cleveland OH; Houston TX; Tampa FL; Fort Lauderdale-Miami FL). Health literacy was measured using the short form of the Test of Functional Health Literacy in Adults. Behaviors investigated included self-reported cigarette smoking, alcohol consumption, physical activity, body mass index, and seat belt use. Individuals with inadequate health literacy were more likely to have never smoked (46.7% vs. 38.6, p =0.01); to completely abstain from alcohol (75.6% vs. 57.9, p <0.001); and to report a sedentary lifestyle (38.2% vs. 21.6%, p <0.001) compared to those with adequate health literacy. No significant differences were noted by mean body mass index or seat belt use. In multinomial logistic regression models that adjusted for relevant covariates, inadequate health literacy was not found to be significantly associated with any of the health risk behaviors investigated. Among community-dwelling elderly, limited health literacy was not independently associated with health risk behaviors after controlling for relevant covariates.

Assessment of mechanical conditions in sub-dermal tissues during sitting: A combined experimental-MRI and finite element approach

A common but potentially severe malady afflicting permanent wheelchair users is pressure sores caused by elevated soft tissue strains and stresses over a critical prolonged period of time. Presently, there is paucity of information regarding deep soft tissue strains and stresses in the buttocks of humans during sitting. Strain and stress distributions in deep muscle and fat tissues were therefore calculated in six healthy subjects during sitting, in a double-donut Open-MR system, using a “reverse engineering” approach. Specifically, finite element (FE) models of the undeformed buttock were built for each subject using MR images taken at the coronal plane in a non-weight-bearing sitting posture. Using a second MR image taken from each subject during weight-bearing sitting we characterized the ischial tuberosity sagging toward the sitting surface in weight-bearing, and used these data as displacement boundary conditions for the FE models. These subject-specific FE analyses showed that maximal tissue strains and stresses occur in the gluteal muscles, not in fat or at the skin near the body–seat interface. Peak principal compressive strain and stress in the gluteus muscle were 74±7% and 32±9 kPa (mean±standard deviation), respectively. Peak principal compressive strain and stress in enveloping fat tissue were 46±7% and 18±4 kPa, respectively. Models were validated by comparing measured peak interface pressures under the ischial tuberosities (17±4 kPa) with those calculated by means of FE (18±3 kPa), for each subject. This is the first study to quantify sub-dermal tissue strain and stress distributions in sitting humans, in vivo. These data are essential for understanding the aetiology of pressure sores, particularly those that were recently termed “deep tissue injury” at the US National Pressure Ulcer Advisory Panel (NPUAP) 2005 Consensus Conference.

Modeling of car seat and human body interaction under rear impact

The development of new protective systems must be performed on reliable tools and representative of an alive human. It is clear and often addressed in the literature that under such an impact configuration, the deformation of the torso and the car seat is of extreme importance and defines the initial conditions of the head–neck system. To address this issue, an original lumped model of the human torso was developed and coupled to a car seat–head rest complex. The modal analysis of the human torso in a seating position conduced by Kitazaki and Griffin in 1998 was used in this study for both masses and mechanical properties identification. This model of minimum complexity, able to reproduce the five first experimental vibration modes, was validated in the frequency domain in terms of natural frequencies and damping as well as mode shapes. In addition to the lumped approach, an external geometry of the human torso was implemented to couple the human body model to a finite element model of the car seat also developed in this study. Rear impact simulation permits it to observe realistic body behavior and accurate T1 acceleration, an essential aspect in real-world accident reconstruction, and seat–head rest evaluation and optimization against neck loading.

Gender-based differences in postural responses to seated exposures

Individuals may respond differently to various chair designs and the factors that influence these sitting behaviours are not well understood. There is very little information in the scientific literature regarding the observation and documentation of gender differences in seated postures. In particular, anecdotal observations of potential gender-specific sitting behaviours led us to test the influence of gender on the postural responses to different seated conditions. Sixteen healthy university students (8 males and 8 females) were tested on four different chair configurations. Upper body kinematics (spine angles and centre of mass) and seat pressure profiles (centre of pressure, peak pressure) were obtained during each testing session. Regardless of the chair used or the task performed, average lumbar and trunk angles were significantly more flexed for males than for females (P=0.047 and P=0.0026, respectively). Males exhibited average lumbar spine and trunk angles of 65.4 degrees (SD 16.2 degrees ) and 29.8 degrees (SD 28.3 degrees ), respectively, while female lumbar spine and trunk angles were 49.6 degrees (SD 23.1 degrees ) and -3.3 degrees (SD 20.4 degrees ), respectively. The pelvis was posteriorly rotated for males (7.6 degrees (SD 8.2 degrees )) and anteriorly rotated for females (-5.5 degrees (SD 9.3 degrees )) (P=0.0008). Significant gender *chair interactions of the location of the individual on the chair seat were most marked for the pivoting chair with a back rest. Females positioned their centre of mass and hip joints anterior to the chair pivot point while males' centre of mass (P=0.0003) and hip joints (P=0.0039) were located posterior to the pivot point. Females also sat with their centre of mass closer to the seat pan centre of pressure than males when a back rest was present (P=0.0012). Males and females may be exposed to different loading patterns during prolonged sitting and may experience different pain generating pathways. Therefore, gender-dependent treatment modalities and/or coaching should be implemented when considering methods of reducing the risk of injury or aggravation of an existing injury.

Analysis of pressure distribution at the body–seat interface in able-bodied and paraplegic subjects using a deformable active contour algorithm

In this paper, a semi-automatic method for segmenting pressure distribution image-based data at the body–seat interface is presented. The purpose of this work was to estimate the surface and the load supported by the ischial tuberosity (IT) region. The proposed method involves three steps: (1) detecting the IT region using a pressure-distribution image gradient; (2) estimating the contour of the IT region by an iterative active contour algorithm and finally (3) estimating the percentage of the surface and the weight-bearing of the IT region in a group of able-bodied (AB) and spinal-cord injury (SCI) subjects. It was found in this study that the weight bearing on the IT for the spinal-cord injured group is distributed on half the surface in comparison with the AB group or the powered wheelchair users groups. The findings of this study provide insights concerning pressure distribution in sitting for the paraplegic and able-bodied.

PRESSURE DISTRIBUTION ON WHEELCHAIR CUSHIONS IN STATIC SITTING AND DURING MANUAL PROPULSION

Quantification of biomechanical parameters by describing interactions between a wheelchair user and his cushion is important to prevent pressure sores in a better way and to match the needs of the subjects in terms of comfort and mobility. This paper presents the method and the results of a biomechanical analysis through the pressure maps at the body–seat interface of a antidecubitus wheelchair cushion on a group of eight patients (affected by SCI or Multiple Sclerosis) during autonomous wheelchair propulsion. In general, our results confirm that mobility is an important factor for ulcer prevention because passing from the static sitting posture to propulsion the mean pressure decreases and there is a redistribution of the load at lower pressure values. Moreover this represents a useful approach for the customized choice and adaptation of the antidecubitus aids.

An Experimental Setup to Parameterize and Simulate Upholstered Seats

The increasing number of 3D-CAD-systems integrating computer based man models make it possible to evaluate the design of the man machine interface in an early state. The interaction of human and seat is not simulated in a satisfying way yet due to the extreme complexity of the task. At the Lehrstuhl für Ergonomie, Technische Universität München an experimental setup has been developed to investigate this interaction systematically. With the help of this setup upholstered seats can be parameterized by their spring characteristics and geometry to be simulated as physical representation of the seat with the same setup. Pressure distributions and deflection profiles can be measured with integrated sensors. The simulated seat also provides the possibility to vary the seat characteristics systematically. The experimental setup consists of two cushion units, adjustable in size and angle. Each unit consists of 9 by 9 adjustable positioning units, technically realized as programmable springs. Tests with selected positioning units have shown that the accuracy of positioning, as well as the accuracy of the measured and simulated spring characteristics is sufficient. Existing seat cushions have been simulated. Based on mathematical indices the similarity of measured pressure distributions on the simulated cushions and the corresponding seats were compared. Based on this results it can be stated that the characteristics of real seats can be simulated with sufficient accuracy. So it is possible to use the experimental setup as a tool to gain the necessary data to model the interaction between the human body and upholstered seats. Further research is going to be performed on the modeling according to the physical parameters geometry and spring characteristics of the seat as well as the pressure distribution and deflection profiles caused by the subjects interacting with the seat.

Preferred Driving Posture and Driver's Physical Dimension

This study collected the data concerning preferred driving postures and adopted seat adjustment levels. Then, the relationships among drivers' body sizes, postural angles, positions and angles of the seat, and body pressure distribution were investigated. An experiment was conducted to find observed optimum driving posture, seat adjustment level, and body pressure. Thirty-six subjects (20 males, 16 females) were selected to be representative of the automotive driving population of Korea. The preferred ranges for optimum postural comfort of Korean were presented. Considering the relationships among body sizes, driving postures, and seat adjustment levels, there was trade-off on the comfortable driving posture between steering wheel handling and pedal operation. Estimation models on observed optimum driving posture and seat adjustment level were constructed. The developed models enable us to estimate the quantitative optimum driving posture and seat adjustment level with a certain driver's physical dimensions.