Standards and Anthropometry for Wheeled Mobility

UDI

The research sample was recruited from disability and senior organizations in Winnipeg by written invitation. The organizations were not reported. Participants were measured in their own devices. All participants were paid $50 and travel expenses. Of the 50 individuals studied, 35 used power chairs and 15 used scooters. The cause of disability for individuals in the sample included a wide range of conditions. The largest group represented was Cerebral Palsy (15 individuals or 24% of the sample). The research was conducted in February.

All dimensions were taken to the extremes of the equipment including any object attached to the device like a ventilator. However, the actual landmarks on the devices are not well documented. Measurements were made with rulers and tape measures but no information is given on the accuracy and reliability of these techniques. Maneuvering trials were recorded using overhead video cameras while participants completed standardized movements in simulated environments built with plywood floors and wood framed dividers. Measurements were later taken off the videotapes although the method used to do this and the reliability of the technique are not described. An observer rating was used to determine successful trials.

Maneuvering trials were recorded using overhead video cameras. Except for one, the maneuvering experiments were completed within simulated environments built with plywood floors and wood framed dividers faced with fiberboard and covered with construction paper. The starting clearance for each trial was the minimum clearance of the Canadian CSA B651-95 Standard. Each participant completed two trials for each clearance but which was used for analysis is not reported. Observers rated the level of accessibility of each trial on a scale devised by the researchers. No information is provided regarding the inter-rater or intra-rater reliability of the scale. “Very accessible” as defined by the scale meant that the participant was able to drive the device through the test environment without stopping, reversing or touching walls/obstacles. No hesitation or reduction in speed was allowed to achieve that rating. If the trial was not rated “very accessible” the clearance between dividers was increased an increment of 25 mm until, presumably, they reached that level of performance.

The width of travel required for passage was studied for the device user alone, for two device users and for a “pedestrian” and a device user. No information is provided on the size of the other person or how close to the adjoining wall they passed. Although shoulder “widths” was measured, the report does not define that dimension. Several different types of turns were studies:  a 360 degree turn in free space, a three point (K turn) between two corridor walls, two 90 degree turns around an obstacle that was 1200 mm wide, two 90 degree turns around an obstacle that was narrower than1200 mm, 90 degree turn on a ramp landing, and a 180 degree turn on a ramp landing. The 360 degree turn was conducted both in the clockwise and counter clockwise direction. The 360 degree turn diameter was estimated by using the video image and the measured size of the wheelchair. It was noted that arms and elbows often protruded outside the arc of the chair. The additional space required for limbs was estimated. No indication as whether the estimates were corrected for parallax or distortion in the video lens. Video lenses tend to distort the scene more toward the outside of the lens than toward the middle.

Reach measurements were obtained without touching the individual. Reaching abilities were measured both with and without “bending” although a definition of “bending” was not provided. Side reaching abilities were measured from the center seat back where it met the seat to the “tip of the furthest extended finger or the furthest reach of the participant’s hand.” Forward reach was measured similarly from the point where the seat back meets the seat. No information is provided how the actual reach was completed, e.g. to a target, at a specified angle, with a weight, etc. It is also not clear whether the seat cushion was considered part of the seat or not. And, no mention is made of how measurements were taken in conditions where there was a space between seat back and seat. The accuracy and reliability of the measurements is of particular concern here since standard anthropometric measuring tools were not used and the wheeled mobility device users often have very limited reaching abilities and may not be able to hold their hand and arm in position long enough for an accurate measurement in free space. Without more specific information on the angle or direction of reach, it is very difficult to interpret the results of this research. Furthermore, measuring the point at which the seat back meets the seat is very difficult when an individual is occupying the chair. No information is provided on how that was accomplished.