The Anthropometrics of Disability - Designing Accessible Communities

fatigue on reaching ability nor do they reflect variations in gait or abilities to propel and
maneuver a wheelchair. For these reasons, correlations between muscle strength and
structural anthropometric measurements are very low.
Functional anthropometry expands on structural data to provide information on the actual
reach trajectories and envelopes and clearances needed to move through a space and
manipulate parts of the environment. It also includes examining the relationship between
the application of force and movement. So, for example, researchers at the RERC on
Wheeled Mobility and the Center for Ergonomics are studying the dynamics of propelling
manual wheelchairs and repetitive reaching tasks. This involves modeling the shoulder and
the pelvis under stress. Such models will provide an understanding of how to reduce
injuries and accidents for wheelchair users.
An important area of functional anthropometry that has been neglected is the
development and use of outcome measures. Two types of outcome measures can be
devised, observational measures and psychophysical measures. The former include
indicators of satisfactory performance like hitting a target or placing an item on shelf or
observer evaluations, e.g. level of assistance needed. The latter are subjective rating
scales that provide an indicator of what the participant thinks about the task being
performed, e.g. level of comfort or acceptance. Outcome measures requiring observer
judgement or subjective opinion are subject to bias and error due to intra rater variation
(same person rates the same thing differently at different times), inter rater differences
(different people rate the same thing differently) or lack of sensitivity (scale doesn’t pick
up real differences). Rigorous development and testing are necessary to insure that
outcome measures are effective.
COLLECTING RELIABLE AND VALID DATA
Some argue that functional concerns can be examined with computer animations of people
in movement. Animations, unlike anthropometric models, a re not tied to databases of
measurements or computational models of movement and biomechanics. Rather, the
motions and sizes of the figures are based on some rough assumptions about the size of
people and assistive devices and the way people move. Computer animation is very
convincing and useful for illustrative purposes but the external validity and
generalizability to large populations is questionable. If an image looks good on a
computer screen, it will often be accepted as fact even though it is not an accurate
representation of how real people move and function. A true human figure model is
parametric. Body sizes can be scaled to represent data collected from real people. It also
uses computational techniques to produce movement based on kinematic and b iomechanic
abilities.
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