Pressure thresholds and stiffness on the plantar surface of the human foot

Abstract

A methodology to assess Pressure Discomfort Thresholds (PDT), Pressure Pain Thresholds (PPT) and tissue stiffness on the plantar surface of the foot was developed. Ten male and 10 female participants volunteered for the study. Foot landmarks were used to create a standardised grid-type template of 95 points. For each test point, PPT and PDT values were obtained, and stiffness was calculated for each of the 20 participants. Cluster analyses were performed to determine the regions of similarity for the three dependent variables, PPT, PDT and stiffness. Moran’s-I-index was used to determine the spatial auto correlations. The use of k-means clustering showed five distinct clusters while the three dependent variables showed strong correlations to each other. Morisita’s similarity index was used to check the similarity of the grid among all participants. Both male and female participants showed a Morisita’s index greater than 0.7 confirming the reliability of the foot template.

Practitioner Summary: Pressure Discomfort thresholds (PPT), Pressure pain thresholds (PPT) and tissue stiffness were evaluated at 95 points on the plantar surface of the foot. The PPT and related PDT map are useful to design the footbeds of shoes. Based on the data collected, five distinct clusters of locations were identified.     

Effects of external light load on posture and foot pressure distribution in young adults: A pilot study

Holding an asymmetrical load, like a rucksack, grocery bag, or travel backpack, is a part of daily and occupational activities. This pilot study was aimed to determine the effects of light, asymmetrical, handheld load on the body posture and foot pressure distribution in young adults. Thirteen young volunteers, free of any injury or pain, took part in the study (aged 21.53 ± 1.10 years). All the study participants were right-handed. An additional load (4 kg, placed in the rucksack) was asymmetrically held in each hand while standing still. For evaluation of the posture and foot pressure distribution, the investigation focused on three positions, i.e., no-load, a rucksack in the right hand, a rucksack in the left hand. We used a surface topography system and force platform for evaluation of the body posture and foot pressure examination, respectively. The results showed that the main changes in the body posture caused by an external load application manifested in trunk imbalance. The trunk was shifted in the direction opposite to the load. Trunk imbalance changes were statistically significant in all three comparisons (p = 0.001). Interestingly, changes in the rotations and lateral deviation seem to be dependent on the hand dominance. Greater foot pressure was observed on the loaded limb (p < 0.01), and highly significant differences were noted between the left and right foot in both loaded postures (p < 0.001). Further research needs to be done to check if lateralization is connected with body posture while holding an external load.     

基于新型免疫粒子群优化的热连轧负荷分配策略*

针对带钢热连轧精轧中的负荷分配问题,提出了一种新型的优化策略。首先提出了一种新型的免疫粒子群混合优化算法,通过克隆选择算子来调节群体的浓度,实现混合算法的个体高亲和力和群体的多样性; 然后通过提出的混合算法对负荷分配进行优化,得到优化的压下量数据,通过这些数据建立了计算负荷分配输出的人工神经网络。实验表明,提出的混合算法和负荷分配优化策略给出了很好的优化效果,能有效地指导实际生产应用。     

The assessment of material handling strategies in dealing with sudden loading: influences of foot placement on trunk biomechanics

Sudden unexpected loading has been identified as a risk factor of work-related low back pain (LBP). This study investigated the effects of different foot placements and load-releasing locations on trunk biomechanics under an unexpected sudden loading event. Fifteen subjects experienced sudden release of a 6.8-kg external load from symmetric or asymmetric directions while maintaining four different foot placements. The results showed that subjects experienced on average 4.1° less trunk flexion, 6.6 Nm less L5/S1 joint moment and 32.0 N less shear force with staggered stance with the right foot forward (the most preferred placement) compared with wide stance (the least preferred placement). Asymmetric load-releasing positions consistently resulted in smaller impacts on trunk biomechanics than symmetric positions. The findings suggest that staggered stance and asymmetric load-holding position can be used as a protective load-handling posture against LBP caused by sudden loading.     

Research to reality: a critical review of the validity of various criteria for the prevention of occupationally induced low back pain disability

Criteria have been suggested to reduce the incidence, or severity of low back pain disability. Five underlying theories for such criteria have been identified in the literature, and a critical review of the validity of these criteria has been carried out. Despite attributions elsewhere, peer-reviewed validation of the various criteria range from modest to nil. The need for a validation criterion for use in workplace design in order to reduce low back pain disability, or severity, is identified and the need for an international protocol to allow cross-study validation of present and future criteria is suggested.     

The impact of a sloped surface on low back pain during prolonged standing work: A biomechanical analysis

Background

Occupations that require prolonged periods of standing have been associated with increased reports of musculoskeletal disorders including low back pain. Previous work has utilized a prospective design of functionally inducing low back pain in previously asymptomatic individuals during a prolonged standing task. Increased trunk and gluteus medius muscle co-activation has been found in previously asymptomatic individuals who developed pain during standing compared with individuals who did not develop pain.

Purpose

The purpose of this study was to investigate the subjective and biomechanical responses of known pain developers and non-pain developers (previously determined during level standing) when exposed to the same prolonged standing task protocol completed while standing on a ±16° sloped surface.

Results

Overall low back pain scores were reduced by 59.4% for the pain development group, identified in level standing, when using the sloped surface. There was a marked decrease in the co-activation of the bilateral gluteus medius muscles in the known pain developers when standing on the sloped surface compared with level standing. However the non-pain developer group responded in the opposite direction by having an increase in the co-activation of these muscles, although they did not have a commensurate increase in low back pain. There were changes in both the postural and joint-loading variables examined. These changes were minimal and in most cases the sloped surface produced responses that bracketed the postures and loading magnitudes found in level standing depending on whether the participant was standing on the +16° or −16° surface.

Conclusions

The sloped surface resulted in decreased subjective low back pain during prolonged standing. There were also associated biomechanical changes resulting from using a sloped surface during prolonged standing. These positive findings were supported in an exit survey satisfaction rating with 87.5% indicating that they would use the sloped surface if they were in an occupational setting that required prolonged standing work.     

A randomised approach for NARX model identification based on a multivariate Bernoulli distribution

The identification of polynomial NARX models is typically performed by incremental model building techniques. These methods assess the importance of each regressor based on the evaluation of partial individual models, which may ultimately lead to erroneous model selections. A more robust assessment of the significance of a specific model term can be obtained by considering ensembles of models, as done by the RaMSS algorithm. In that context, the identification task is formulated in a probabilistic fashion and a Bernoulli distribution is employed to represent the probability that a regressor belongs to the target model. Then, samples of the model distribution are collected to gather reliable information to update it, until convergence to a specific model. The basic RaMSS algorithm employs multiple independent univariate Bernoulli distributions associated to the different candidate model terms, thus overlooking the correlations between different terms, which are typically important in the selection process. Here, a multivariate Bernoulli distribution is employed, in which the sampling of a given term is conditioned by the sampling of the others. The added complexity inherent in considering the regressor correlation properties is more than compensated by the achievable improvements in terms of accuracy of the model selection process.     

Association between pain intensity in the neck and components of a workstation: A cross-sectional study on Japanese office workers

This study aimed to investigate the association between inappropriate workstation components and neck pain intensity. This cross-sectional study was conducted on 309 Japanese office workers. Workstation questionnaires were developed based on previous studies and consisted of 11 items that assessed the armrest, monitor screen, desk, and keyboard. For each of the 11 items, we defined whether the item was “inadequate” based on previous studies. Neck pain experienced was measured using a numerical rating scale (NRS) of 0–10, and the NRS scores were categorized into three (0: “no pain,” 1–3: “low pain intensity,” and 4–10: “high pain intensity”). Crude and adjusted ordered logistic regressions were used to determine the association between the inadequate workstation and neck pain intensity. In the first analysis model, each item of the workstation questionnaire was used as an explanatory variable. Then, in the second analysis model, the number of inadequate workstation components was used as the explanatory variable. Ordered logistic regression analyses showed that the distance of the eye to the monitor was significantly associated with neck pain intensity (crude, OR: 2.21; 95% CI: 1.41–3.19; adjusted, OR: 1.79; 95%CI: 1.08–2.50). The number of inadequate workstation components had a significant positive association with neck pain intensity (crude, OR: 1.19, 95%CI: 1.04–1.34; adjusted, OR: 1.15, 95% CI: 1.00–1.32). The results of this study suggest that the distance between the eye and the monitor might be the most important workstation factor contributing to neck pain, and workstation components should be assessed collectively.     

Participation in workplace design with reference to low back pain: a case for the improvement of the police patrol car

Thirty Canadian police officers, divided into six groups, participated in the redesign of the interior of the patrol car. Three of the groups consisted of individuals having a history of low back disease. The effect of participating in a design process on the characteristics of the final design and on the perception of the low back pain was studied in a semi-experimental setting. The participants developed a strong commitment to the participatory design process, which was reflected in their productions. The differences between participants with and without a history of a low back disease was not marked. The former tended to stress posture-related elements in their analysis and design.     

The effect of dynamic sitting on the prevention and management of low back pain and low back discomfort: a systematic review

Dynamic sitting has been proposed to reduce low back pain (LBP) and/or low back discomfort (LBD) while sitting. This is supported by studies suggesting that subjects with LBP assume more static, sustained postures while sitting. This systematic review investigated the effect of dynamic sitting on LBP among subjects with LBP and the development of LBD among pain-free subjects. Electronic databases were searched by two independent assessors. All prospective studies which compared the effect of a dynamic sitting condition on LBP or LBD to another sitting condition were eligible, with no minimum follow-up period applied. The quality of the included studies was assessed using the PEDro scale. Seven high-quality studies were eligible, including five crossover studies and two randomised controlled trials. The results suggest there is currently no evidence to support the use of dynamic sitting as a stand-alone approach in the management of LBP. PRACTITIONER SUMMARY: This systematic review investigated the effect of dynamic sitting on LBP or LBD. Seven high-quality studies met the inclusion and exclusion criteria. Overall, the evidence suggests that dynamic sitting approaches are not effective as a stand-alone management approach for LBP.     

City bus driving and low back pain: a study of the exposures to posture demands, manual materials handling and whole-body vibration

A cross-sectional study was conducted to investigate worker exposure to posture demands, manual materials handling (MMH) and whole body vibration as risks for low back pain (LBP). Using validated questionnaire, information about driving experience, driving (sitting) posture MMH, and health history was obtained from 80 city bus drivers. Twelve drivers were observed during their service route driving (at least one complete round trip) and vibration measurements were obtained at the seat and according to the recommendations of ISO 2631 (1997), for three models of bus (a mini-bus, a single-decker bus, a double-decker bus). The results showed that city bus drivers spend about 60% of the daily work time actually driving, often with the torso straight or unsupported, perform occasional and light MMH, and experience discomforting shock/jerking vibration events. Transient and mild LBP (not likely to interfere with work or customary levels of activity) was found to be prevalent among the drivers and a need for ergonomic evaluation of the drivers' seat was suggested.     

Predicting passenger seat comfort and discomfort on the basis of human,context and seat characteristics: a literature review

Abstract

This literature review focused on passenger seat comfort and discomfort in a human–product–context interaction. The relationships between anthropometric variables (human level), activities (context level), seat characteristics (product level) and the perception of comfort and discomfort were studied through mediating variables, such as body posture, movement and interface pressure. It is concluded that there are correlations between anthropometric variables and interface pressure variables, and that this relationship is affected by body posture. The results of studies on the correlation between pressure variables and passenger comfort and discomfort are not in line with each other. Only associations were found between the other variables (e.g. activities and seat characteristics). A conceptual model illustrates the results of the review, but relationships could not be quantified due to a lack of statistical evidence and large differences in research set-ups between the reviewed papers.

Practitioner Summary: This literature review set out to quantify the relationships between human, context and seat characteristics, and comfort and discomfort experience of passenger seats, in order to build a predictive model that can support seat designers and purchasers to make informed decisions. However, statistical evidence is lacking from existing literature.     

The development of a model to predict the effects of worker and task factors on foot placements in manual material handling tasks

Accurate prediction of foot placements in relation to hand locations during manual materials handling tasks is critical for prospective biomechanical analysis. To address this need, the effects of lifting task conditions and anthropometric variables on foot placements were studied in a laboratory experiment. In total, 20 men and women performed two-handed object transfers that required them to walk to a shelf, lift an object from the shelf at waist height and carry the object to a variety of locations. Five different changes in the direction of progression following the object pickup were used, ranging from 45° to 180° relative to the approach direction. Object weights of 1.0 kg, 4.5 kg, 13.6 kg were used. Whole-body motions were recorded using a 3-D optical retro-reflective marker-based camera system. A new parametric system for describing foot placements, the Quantitative Transition Classification System, was developed to facilitate the parameterisation of foot placement data. Foot placements chosen by the subjects during the transfer tasks appeared to facilitate a change in the whole-body direction of progression, in addition to aiding in performing the lift. Further analysis revealed that five different stepping behaviours accounted for 71% of the stepping patterns observed. More specifically, the most frequently observed behaviour revealed that the orientation of the lead foot during the actual lifting task was primarily affected by the amount of turn angle required after the lift (R ² = 0.53). One surprising result was that the object mass (scaled by participant body mass) was not found to significantly affect any of the individual step placement parameters. Regression models were developed to predict the most prevalent step placements and are included in this paper to facilitate more accurate human motion simulations and ergonomics analyses of manual material lifting tasks.

Statement of Relevance: This study proposes a method for parameterising the steps (foot placements) associated with manual material handling tasks. The influence of task conditions and subject anthropometry on the foot placements of the most frequently observed stepping pattern during a laboratory study is discussed. For prospective postural analyses conducted using digital human models, accurate prediction of the foot placements is critical to realistic postural analyses and improved biomechanical job evaluations.     

Critical velocity of a load moving on a beam with a sudden change of foundation stiffness: Applications to high-speed trains

The transient dynamic response of a beam supported on a foundation with sudden stiffness change and subjected to a force moving with constant velocity is analysed. The abrupt change is located at the mid-section of the beam of finite length. Two analytical approaches are implemented. In the first one, the response is obtained by finite integral transformations incorporating global modes of vibration, while in the second the analytical responses of each half of the beam are linked by continuity conditions. The values obtained are used to study the influence of the abrupt change on the critical velocities. The analyses carried out enable to reach results and draw conclusions directly related to the knowledge of ground vibrations induced by high-speed trains.     

A version of a nuclear optical model code for small computers designed to run on a PDP-15

Title of program: OPTIX KSU 1 Catalogue number: ACRR Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland (see application form in this issue). Computer: PDP-15; Installation: Department of Physics, Kansas State University, Manhattan, Kansas, USA. Operating system: BF Programming language used: Fortran IV High speed storage required: 14K words No. of bits in a word: 18 for integer variable. 2 words per floating-point variable. Overlay structure: Overlaid No. of magnetic tapes required: 2 PDP DEC tapes Other peripherals used: Lineprinter, typewriter, storage oscilloscope images No. of card images in combined program and test deck: 3660 Card punching code: ASCII Reference to other published version of this program:

     

17.

From laser-scanned data to feature human model: a system based on fuzzy logic concept     

Charlie C.L. Wang ^{Author Vitae}  Terry K.K. Chang Author VitaeAuthor Vitae 《Computer aided design》2003,35(3):241-253

This paper describes the development of a prototype system using fuzzy logic concept for constructing a feature human model, which is to be stored in a 3D digital human model database. In our approach, the feature human model is constructed by unorganized cloud points obtained from 3D laser scanners. Firstly, noisy points are removed, and the orientation of the human model is adjusted; secondly, a feature based mesh generation algorithm is applied on the cloud points to construct the mesh surface of a human model; lastly, semantic features of the human model are extracted from the mesh surface. Compared with earlier approach, our method strongly preserves the topology of a human model; more details can be constructed; and both the robustness and the efficiency of the algorithm are improved. At the end of the paper, in order to demonstrate the functionality of feature human models, potential applications are given.     

18.

Influence diagnostics for random effect survival models: Application to a recurrent infection study for kidney patients on portable dialysis     

Liming Xiang  S.K. Tse 《Computational statistics & data analysis》2007,51(12):5977-5993

In modeling multivariate failure time data, a class of survival model with random effects is applicable. It incorporates the random effect terms in the linear predictor and includes various random effect survival models as special cases, such as the random effect model assuming Cox's proportional hazards, with Weibull baseline hazards and with power family of transformation in the relative risk function. Residual maximum likelihood (REML) estimation of parameters is achieved by adopting the generalised linear mixed models (GLMM) approach. Accordingly, influence diagnostics are developed as sensitivity measures for the REML estimation of model parameters. A data set of recurrent infections of kidney patients on portable dialysis illustrates the usefulness of the influence diagnostics. A simulation study is carried out to examine the performance of the proposed influence diagnostics.     

19.

Polynomial expansion Monte Carlo study of frustrated itinerant electron systems: Application to a spin-ice type Kondo lattice model on a pyrochlore lattice     

Hiroaki Ishizuka  Masafumi Udagawa  Yukitoshi Motome 《Computer Physics Communications》2013

We present the benchmark of the polynomial expansion Monte Carlo method to a Kondo lattice model with classical localized spins on a geometrically frustrated lattice. The method enables us to reduce the calculation amount by using the Chebyshev polynomial expansion of the density of states compared to a conventional Monte Carlo technique based on the exact diagonalization of the fermion Hamiltonian matrix. Further reduction is brought about by a real-space truncation of the vector–matrix operations. We apply the method to the model with spin-ice type Ising spins on a three-dimensional pyrochlore lattice and carefully examine the convergence in terms of the order of polynomials and the truncation distance. We find that, in a wide range of electron density at a relatively weak Kondo coupling compared to the noninteracting bandwidth, the results by the polynomial expansion method show good convergence to those by the conventional method within reasonable numbers of polynomials. This enables us to study the systems up to 4×8³=2048$4\times 8^3=2048$ sites, while the previous study by the conventional method was limited to 4×4³=256$4\times 4^3=256$ sites. On the other hand, the real-space truncation is not helpful in reducing the calculation amount for the system sizes that we reached, as the sufficient convergence is obtained when most of the sites are involved within the truncation distance. The necessary truncation distance, however, appears not to show significant system size dependence, suggesting that the truncation method becomes efficient for larger system sizes.     

20.

Design and development of a technology enhanced hybrid instruction based on MOLTA model: Its effectiveness in comparison to traditional instruction     

Omer Delialioglu  Zahide Yildirim 《Computers & Education》2008

Using the model for learning and teaching activities (MOLTA), a new technology enhanced hybrid instruction was designed, developed and implemented. The effectiveness of the hybrid instruction in regard to students’ achievement, knowledge retention, attitudes towards the subject, and course satisfaction was evaluated in comparison to traditional classroom instruction. Experimental study with pre-test, post-test control group design was carried out. The sample of the study consisted of 50 university students enrolled in “Computer Networks and Communication” course. The control and experimental groups composed of 24 and 26 students respectively, and the experiment lasted 14 weeks. The findings of the study indicated no significant difference between the hybrid course and the traditional course in students’ achievement, knowledge retention, satisfaction, and attitude.     

Catalogue no.:	Title:	Ref. in CPC:
ABOU	OPTICS	5 (1973) 69

From laser-scanned data to feature human model: a system based on fuzzy logic concept

This paper describes the development of a prototype system using fuzzy logic concept for constructing a feature human model, which is to be stored in a 3D digital human model database. In our approach, the feature human model is constructed by unorganized cloud points obtained from 3D laser scanners. Firstly, noisy points are removed, and the orientation of the human model is adjusted; secondly, a feature based mesh generation algorithm is applied on the cloud points to construct the mesh surface of a human model; lastly, semantic features of the human model are extracted from the mesh surface. Compared with earlier approach, our method strongly preserves the topology of a human model; more details can be constructed; and both the robustness and the efficiency of the algorithm are improved. At the end of the paper, in order to demonstrate the functionality of feature human models, potential applications are given.     

Influence diagnostics for random effect survival models: Application to a recurrent infection study for kidney patients on portable dialysis

In modeling multivariate failure time data, a class of survival model with random effects is applicable. It incorporates the random effect terms in the linear predictor and includes various random effect survival models as special cases, such as the random effect model assuming Cox's proportional hazards, with Weibull baseline hazards and with power family of transformation in the relative risk function. Residual maximum likelihood (REML) estimation of parameters is achieved by adopting the generalised linear mixed models (GLMM) approach. Accordingly, influence diagnostics are developed as sensitivity measures for the REML estimation of model parameters. A data set of recurrent infections of kidney patients on portable dialysis illustrates the usefulness of the influence diagnostics. A simulation study is carried out to examine the performance of the proposed influence diagnostics.     

Polynomial expansion Monte Carlo study of frustrated itinerant electron systems: Application to a spin-ice type Kondo lattice model on a pyrochlore lattice

We present the benchmark of the polynomial expansion Monte Carlo method to a Kondo lattice model with classical localized spins on a geometrically frustrated lattice. The method enables us to reduce the calculation amount by using the Chebyshev polynomial expansion of the density of states compared to a conventional Monte Carlo technique based on the exact diagonalization of the fermion Hamiltonian matrix. Further reduction is brought about by a real-space truncation of the vector–matrix operations. We apply the method to the model with spin-ice type Ising spins on a three-dimensional pyrochlore lattice and carefully examine the convergence in terms of the order of polynomials and the truncation distance. We find that, in a wide range of electron density at a relatively weak Kondo coupling compared to the noninteracting bandwidth, the results by the polynomial expansion method show good convergence to those by the conventional method within reasonable numbers of polynomials. This enables us to study the systems up to 4×8³=2048$4\times 8^3=2048$ sites, while the previous study by the conventional method was limited to 4×4³=256$4\times 4^3=256$ sites. On the other hand, the real-space truncation is not helpful in reducing the calculation amount for the system sizes that we reached, as the sufficient convergence is obtained when most of the sites are involved within the truncation distance. The necessary truncation distance, however, appears not to show significant system size dependence, suggesting that the truncation method becomes efficient for larger system sizes.     

Design and development of a technology enhanced hybrid instruction based on MOLTA model: Its effectiveness in comparison to traditional instruction

Using the model for learning and teaching activities (MOLTA), a new technology enhanced hybrid instruction was designed, developed and implemented. The effectiveness of the hybrid instruction in regard to students’ achievement, knowledge retention, attitudes towards the subject, and course satisfaction was evaluated in comparison to traditional classroom instruction. Experimental study with pre-test, post-test control group design was carried out. The sample of the study consisted of 50 university students enrolled in “Computer Networks and Communication” course. The control and experimental groups composed of 24 and 26 students respectively, and the experiment lasted 14 weeks. The findings of the study indicated no significant difference between the hybrid course and the traditional course in students’ achievement, knowledge retention, satisfaction, and attitude.