A comparison of approaches to reweighting anthropometric data

The objective of this work is to identify the most effective techniques for reweighting anthropometric data such that it accurately represents a target user population. Seven methods are compared, including uniform weighting, stratification and permutations of nearest neighbour (NN) reweighting. The analysis illuminates the performance of existing and novel approaches to reweighting data specifically for approximating body size and shape ('anthropometry'). While uniform weighting and stratified sampling are often used in this field, the present analysis indicates that lower-order NN approaches will produce more representative results. Although anthropometric data are crucial to the design of artefacts, tasks and environments, finding appropriate representative data is challenging. Designers and ergonomists are unlikely to find data that are simultaneously accessible, up-to-date, detailed and from the relevant population. The application of new statistical weights - reweighting - is one useful strategy for meeting this shortfall. This research indicates the best methods for reweighting and provides guidance for sampling strategies in future data collection efforts. Practitioner Summary: Reweighting anthropometric data is one strategy for matching available data to a target user population. Stratified sampling is often used as the method for calculating weights, but it has been shown to produce inaccurate estimates. This research examines seven strategies and finds low-order NN approaches are the more accurate methods.

The effects of seat width, load factor, and passenger demographics on airline passenger accommodation

The objective of this work is to demonstrate a method for examining the competing effects of secular trends in body size, seat size and configuration, and the increased load factor of aeroplanes. The method uses statistical modelling and virtual fit testing to provide a flexible environment for exploring the impact of various parameters on passenger accommodation. A case study demonstrates the method by exploring the effect of seat width on the accommodation of US civilians (based on seated hip breadth). The case study demonstrates that recent trends of decreasing seat widths and increasing load factors lead to higher disaccommodation. Based on anthropometry and virtual fit, women are also shown to be disproportionately disaccommodated compared to men. Practitioner summary: Airlines are reducing seat width at the same time that individuals worldwide are getting larger. Flights are increasingly crowded, with load factor at a record high. This paper explores the effects of seat width on passenger accommodation under several scenarios involving load factor, demographics, and passenger seating allocation strategies.

Reweighting anthropometric data using a nearest neighbour approach

When designing products and environments, detailed data on body size and shape are seldom available for the specific user population. One way to mitigate this issue is to reweight available data such that they provide an accurate estimate of the target population of interest. This is done by assigning a statistical weight to each individual in the reference data, increasing or decreasing their influence on statistical models of the whole. This paper presents a new approach to reweighting these data. Instead of stratified sampling, the proposed method uses a clustering algorithm to identify relationships between the detailed and reference populations using their height, mass, and body mass index (BMI). The newly weighted data are shown to provide more accurate estimates than traditional approaches. The improved accuracy that accompanies this method provides designers with an alternative to data synthesis techniques as they seek appropriate data to guide their design practice.Practitioner Summary: Design practice is best guided by data on body size and shape that accurately represents the target user population. This research presents an alternative to data synthesis (e.g. regression or proportionality constants) for adapting data from one population for use in modelling another.

A survey of anthropometry and physical accommodation in ergonomics curricula

The size and shape of users are an important consideration for many products and environments. Designers and engineers in many disciplines must often accommodate these attributes to meet objectives such as fit and safety. When practitioners have academic training in addressing these issues, it is typically through courses in Human Factors/Ergonomics (HF/E). This paper investigates education related to physical accommodation and offers suggestions for improvement. A survey was conducted wherein 21 instructors at 18 universities in the United States provided syllabi for 29 courses, which were analysed to determine topics related to anthropometry and resources used for the courses. The results show that within the U.S., anthropometry is covered in the majority of courses discussing physical ergonomics, but important related concepts were often omitted (e.g., digital human modelling, multivariate accommodation and variability across global populations). Curricula could be improved by incorporating more accurate anthropometry, multivariate problems and interactive online tools.

PRACTITIONER SUMMARY

This paper describes a study investigating collegiate ergonomics courses within the U.S. in the area of physical accommodation. Course schedules and texts were studied for their treatment of several topics related to accommodating the spatial requirements (anthropometry) of users. Recommendations are made for improving course curricula.

An updated estimate of the body dimensions of US children

Anthropometric data from children are important for product design and the promulgation of safety standards. The last major detailed study of child anthropometry in the USA was conducted more than 30 years ago. Subsequent demographic changes and the increased prevalence of overweight and obesity render those data increasingly obsolete. A new, large-scale anthropometric survey is needed. As an interim step, a new anthropometric synthesis technique was used to create a virtual population of modern children, each described by 84 anthropometric measures. A subset of these data was validated against limited modern data. Comparisons with data from the 1970s showed significant changes in measures of width and circumference of the torso, arms and legs. Measures of length and measurements of the head, face, hands and feet exhibited little change. The new virtual population provides guidance for a comprehensive child anthropometry survey and could improve safety and accommodation in product design. Practitioner Summary: This research reviews the inadequacies of available sources of US child anthropometry as a result of the rise in the rates of overweight and obesity. A new synthesised database of detailed modern child anthropometry was created and validated. The results quantify changes in US child body dimensions since the 1970s.

Limiting disproportionate disaccommodation in design for human variability

In the design of artefacts, tasks and environments for human use, the body dimensions of the target population are a critical element in spatial optimisation of the design. This study examines how the choices designers make affect the ability of different user groups to safely and effectively interact with a designed artefact. Due to the variability in body size and shape across different demographic groups, heterogeneous user populations are unlikely to experience uniform levels of performance. The associated variability in the rate of unacceptable user conditions is referred to here as disproportionate disaccommodation. This is both an ethical and a performance concern that can partially be addressed through improved design practice. Three methods for incorporating the consideration of user demographics and the corresponding variability in body size and shape are presented. They are compared with a baseline strategy in terms of accommodation and cost.

Considering just noticeable difference in assessments of physical accommodation for product design

Configuring products or environments for the size of their human users requires the consideration of several characteristics of the target user population, including body dimensions (anthropometry) and preferred interaction. Users are both adaptable and imperfect observers, which often makes it difficult for them to distinguish between candidate designs. This insensitivity is described by a concept called 'just noticeable difference', or JND. This paper presents an implementation of JND modelling and demonstrates how its use in the sizing of products or environments for target user populations can improve expected performance. Two facets of this problem are explored: (1) how experimental measures of JND for dimensional optimisation tasks may be obtained, and (2) how measures of JND may be included in models of user-device interaction for both adjustable and discretely sized products and the assumptions required. A case study demonstrating the collection and modelling of JND for a simple univariate problem is also presented. Practitioner Summary: Since people are adaptable and imperfect observers, there exists a 'just noticeable difference' that can be considered when designing products and environments. When JND is modelled for a target population, less variability in design dimensions due to physical user requirements may be necessary. This paper considers JND in quantitative simulations of population accommodation.

The role of anthropometry in designing for sustainability

An understanding of human factors and ergonomics facilitates the design of artefacts, tasks and environments that fulfil their users' physical and cognitive requirements. Research in these fields furthers the goal of efficiently accommodating the desired percentage of user populations through enhanced awareness and modelling of human variability. Design for sustainability (DfS) allows for these concepts to be leveraged in the broader context of designing to minimise negative impacts on the environment. This paper focuses on anthropometry and proposes three ways in which its consideration is relevant to DfS: reducing raw material consumption, increasing usage lifetimes and ethical human resource considerations. This is demonstrated through the application of anthropometry synthesis, virtual fitting, and sizing and adjustability allocation methods in the design of an industrial workstation seat for use in five distinct global populations. This work highlights the importance of and opportunities for using ergonomic design principles in DfS efforts.

PRACTITIONER SUMMARY

This research demonstrates the relevance of some anthropometry-based ergonomics concepts to the field of design for sustainability. A global design case study leverages human variability considerations in furthering three sustainable design goals: reducing raw material consumption, increasing usage lifetimes and incorporating ethical human resource considerations in design.

Center of pressure excursion capability in performance of seated lateral-reaching tasks

BACKGROUND

Seated center of pressure excursion capability can be used for patient evaluation in a clinical setting and in universal design. A quantification of excursion capability across age and anthropometry has not been previously reported, although some research suggests that the ischial tuberosities are the support structure limiting the excursion.

METHODS

Thirty-eight neurologically healthy adults ranging in age from 21 to 74 years and including 12 obese persons performed a series of 6 lateral-reaching tasks. Participants sat on a platform such that their feet did not touch the ground, leaving their legs free to provide counterbalancing support. Data recorded from a force plate under the platform allowed calculation of the center of pressure throughout the trial and the maximum excursion for each condition was recorded.

FINDINGS

The average excursion capability for the healthy, experimental population was 148 mm or 37% of seated hip breadth. Taller participants had larger maximum excursions, on average, than shorter participants, and older participants had smaller excursions than younger participants.

INTERPRETATION

The greater trochanter of the femur-rather than the ischial tuberosities-appears to be the primary support structure limiting center of pressure excursion in lateral, balance-limited reaches without contralateral support. These measures and concepts can be used for design, accommodation, and clinically for patient assessment.