Standards and Anthropometry for Wheeled Mobility

Appendix 1 – Details of Research Methodologies

Bails et al.

Bails recruited participants from attendees at disability support centers and institutions. Participants had to be between 18 and 60 years of age and had to either use a manual or powered wheelchair. Scooter users were not included in the study. The exact sample size is difficult to determine because each sub-study had a different sample size and not all participants were given an ID number. It therefore remains unclear whether or not the total number of participants is the aggregate of the individual studies or if some individuals participated in more than one field test.

Bails’ research focused on testing of full-size simulations of elements found in the built environment, such as doorways, environmental controls, furniture and fixtures. Research findings from many of the field tests used pre-established sizes and features to measure barriers and problems. The research was focused on testing the adequacy of current standards. Many of the findings therefore could not be used to make generalizations or to determine the ideal spaces needed for access. Much of Bails’ data was reported in an incomplete and disorganized manner. For example, hand printed lists of results from each sub-study were included in his report which were difficult to decipher.

Seeger et al.

Seeger et al. (1994) studied only device size. Participants included 240 individuals. About 73% of the sample lived in nursing homes and other institutions. Forty-five percent were over 65. Eleven percent used power chairs and 2% used scooters. Both unoccupied and occupied dimensions of device width and length were measured as well as a set of other basic dimensions. Measurements were taken manually using a tape measure, spirit level and, in some cases, a steel square. No reliability study was completed but the “accuracy” of the measurements is reported to be within 5 mm. 

DETR

The DETR study (Stait et al., 2000) was limited to measurement of device size and weight. Participants were recruited at a “Mobility Roadshow,” an exposition of equipment for people who use wheeled mobility devices for traveling around the community. Of the 745 participants whose data was acceptable, 59% of the sample used self-propelled manual chairs, 9% used attendant powered chairs, 25% used power chairs and 9% used scooters. Nine percent of the sample were judged to be 16 years of age or younger.

The method of data collection was designed to be completed in a very short participation time. A low profile stand was constructed with a weight pad underneath and two cameras mounted above and to the side. Participants were recruited as they walked by the apparatus. They rolled onto the stand and were photographed while their weight was recorded. Then they rolled directly off the stand. A checkerboard was mounted behind the stand from which dimensions could be scaled from photographs. Parallax was corrected during the calculation of the dimensions using scaling from the checkerboard and trigonometry. Prior to data collection the reliability of the method was checked by comparing dimensions taken directly from the person with those calculated from the photographs. The differences between the two sets of dimensions in the reliability study were less than 1%. Although 943 people were photographed, 198 participants’ data were omitted due to camera failure, inability to take accurate dimensions from the photographs, or because the participants had rental wheelchairs.

Wheelchair dimensions were defined clearly. Length was measured from the most anterior to posterior dimension, either body part or device part. Width was the unoccupied width. Height was taken from the ground to the highest point, either chair or person. A major limitation of this study is that, although a wide variety of accessories were observed on the devices, they were not measured as part of the width calculation.

BS8300:2001 Research

Annex D and E to the BS8300:2001 Standard includes informative charts and tables from the results of research commissioned to obtain information on anthropometry of wheeled mobility devices. They include information on space required for “kneeholes,” reaching abilities of wheeled mobility users, clear floor area space requirements and maneuvering clearances. Unfortunately, without a research report with details about the research protocols, it is difficult to interpret and compare the results of this interesting study to the others.

Knee height measured from “floor to top of knee” but it is not clear what anatomical body landmark was used in the knee area and how knee height and location relates to lap height. Footrest depth was measured from “front of wheelchair seat to the front of the toes” but an anatomical landmark on the toes was not identified and information was not provided about how measurements were made when the toe was not as far forward as the footrest or other part of the device (e.g. scooter body) or when footrests did not extend as far as the front wheels. An armrest height landmark is illustrated in the document but it is not clear whether the top was defined as the top of the metal structure of the armrest or an armrest pad. The illustration shows the former. It is also not clear what was measured if the chair had no armrests or slanted armrests.

Reach ranges were measured using a fixed counter height at 750 mm and at three angles of arm reach with respect to the counter. Two conditions, “comfortable” and “extended” were measured. The former did not include stretching or bending from the waist and the latter included stretching and bending but it is not clear whether all participants could do the latter and which hand was used. It is also not clear how individuals were positioned with respect to the counter. No information is given about how the protocol dealt with individuals who could not reach at the specified angles, the landmark on the body used to measure the reach nor the conditions of reaching, e.g. free reach, with a weight, reach to target, open hand, closed fist, etc. No information is provided on the landmark used to measure reach, e.g. tips of fingers or other landmark on the hand.

Clear floor area included the space needed to accommodate wheelchair accessories and the projection of toes beyond footrests and arms and elbows beyond the armrests. It is not clear whether other body parts were included, e.g. knees and legs on scooters. No information is given on the details of the protocol for measuring clear floor area or maneuvering clearances. In particular, it is not clear whether the maneuvers were performed in open space or within some sort of confined space, what constituted a successful trial, how many trials were performed and how the space clearance required was measured. From an illustration, it appears that the protocol for the 180-degree turn did allow participants to perform either a U turn or a K turn.

It appears, from the report of data on the maneuvering trials that some scooters and attendant propelled chairs were included in the sample. It is not clear whether these individuals were included in the device, body or reach measurements.

From basic information gathered with human participants, the researchers developed computer aided design simulations to identify clearances needed for access aisles at vehicles.

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.

IDEA Center

The IDEA study (Steinfeld, Paquet, Feathers, 2004; 2005; Feathers, Paquet, Steinfeld, 2004; Paquet and Feathers, 2004) included static anthropometry of occupied wheeled mobility devices, reach measurements and measurements of maneuvering clearances. At the date of the analyses conducted for this report, 275 participants with a wide range of chronic conditions had been recruited through outreach efforts with several organizations in Western New York and mass media. Fifty-three percent of the sample was male and 47% female. The mean age of the sample was 51.5 with a range of 18-94 years of age. Fifty-five percent used manual wheelchairs, 36% used power wheelchairs and 9% used scooters. Three-dimensional locations of body and wheelchair landmarks were collected with an electromechanical probe (Feathers, Paquet and Steinfeld, 2004). A reliability study was completed before data collection (Feathers, Paquet and Drury, 2004).

Participants were recruited through presentations at organizational meetings, television news, mailers, posters, flyers, brochures and cooperative outreach efforts with several organizations in Western New York that serve people who use wheeled mobility devices. Organizations that helped to recruit participants included the Western New York Independent Living Center, the United Cerebral Palsy Association of Western New York, the Western New York Veterans Administration Medical Center, Eastern Paralyzed Veterans of America and DeGraff Skilled Nursing Facility. Some employees of the University at Buffalo were also recruited. Only those who relied on a wheeled mobility device for their primary means of mobility were eligible for participation. Participants had to be at least 18 years of age. All participants were paid $50 plus travel expenses.

Participants were asked to bring in the chair that they use on a regular basis. Most of the individuals in this study had more than one chair (60%), and many of these people had another type of chair as their alternate (52%). Most of the individuals brought the chair that they would normally use when out in public. Informally, most respondents reported that they had smaller and more maneuverable chairs for use at home. Some individuals did not bring in their footrests (4%) because they prefer not to travel with them.

Analysis of individual participants with very large measurements for length identified two clear “outliers” who were excluded from the sample. One of these individuals needed to have one of his legs extended fully during the measurements. The second had spastic tendencies that made it impossible for him to remain still long enough to take the length measurement accurately. Uncorrectable data conversion problems with software caused additional outliers for several analyses.

The measurement protocol included the collection of wheelchair specifications, demographic information, structural anthropometric information and functional anthropometric information for each participant. Three-dimensional locations of body and wheelchair landmarks were collected with an electromechanical probe. A single origin point on the floor was used to identify the location of all landmarks. Thousands of dimensions can be computed from a limited set of landmarks. This reduced the amount of trials and measurements needed significantly. Photographs were taken of each participant in a variety of positions and video recordings were made of all maneuvering trials.

Body and device landmarks were defined in detail in a manual (Feathers, Paquet and Steinfeld, 2004), which also described how the definitions relate to generally accepted anthropometric landmarks and how they differed for this population. The probe used to record body and device landmark locations with respect to one another and to reference planes (e.g., floor, seat, arm support) was an articulating arm with six degrees of freedom that had a precision of 0.3 mm. The three-dimensional coordinates of each landmark point were recorded by pressing the probe’s activation button three times in rapid sequence.

For the reference planes, a minimum of five points on different locations of the physical plane such as on the floor or on the top of a footrest were recorded to define the plane. Distances between points or reference planes were used to derive estimated widths, heights, and depths of key device characteristics and body dimensions. A reliability study showed that this method of obtaining anthropometric dimensions is reliable but measurements may differ from those obtained with conventional anthropometric measuring devices (Feathers, Paquet and Drury, 2004). This occurs mostly with dimensions near the hands and other body parts that may move slightly during data collection.

Occupied length of devices was calculated by computing the dimension from the extreme rear and forward points on the body or chair. This was usually a toe in the front and the trailing edge of the wheel, backpack or edge of the power base in the rear for manual and power wheelchairs. For scooters, the extreme front point was usually a basket that hung off the handlebars or part of the scooter housing and the extreme rear point was usually the rear edge of the housing. Occupied width of devices was calculated by computing the dimension from the extreme left and right points on the body or the chair with hands in resting position. For manual wheelchairs, including attendant propelled models, this could be the outside edge of the wheel guide, the elbow or the hand. For power chairs it could be the outside edge of the control box, an elbow or other body part extended over the side. For scooters, it could be the outside edge of the device housing, the elbows or the outside surface of the hips or shoulders, if they hung over the housing.

The reach protocol utilized a standardized procedure in which participants utilized an apparatus with a series of five shelves that could be moved in and out from the main part of the device and positioned at 100 mm (4 in.) increments while lifting .46, 1.4 and 2.3 kg (0, 1, 3 and 5 lb.) weights. Reach limits were digitized with the mechanical probe, and, from the data, a reach envelope for each individual was constructed. Standard cylindrical canisters 75 mm (3.5 in.) in diameter were used to assess reaching ability. These weights were empirically derived through a study of common bathroom products. If an individual could not grip the canister, a cuff around the palm and attached to the canister was used. If the cuff could not be used, the individual did not complete the reach protocol except for free reach. If a person was unable to reach above the shoulder, they were excluded from all reaching tasks. This eliminated bias in results due to the inclusion of individuals who could not perform a functional reaching task. In all reaching trials except free reach, individuals were asked to reach as far as they could without endangering their safety or causing pain. Free reach trials were completed without bending or stretching.

An envelope of reaching ability was measured with the individual’s preferred hand. To determine maximum reach, the individual held the canister in their preferred hand and placed it on a shelf at the extreme of reach. Reach was recorded using the probe at the “MCP5”, a bony protuberance at the outside of the hand below the pinky finger. This landmark was used because functional reach involves grasping and manipulating objects and the tip of the fingers does not give a measure of reach that reflects grasping tasks. In calculating the actual reach, we computed the location of the target on the shelf itself using the known dimensions of the target and the reach dimension to the MCP5. Similar trials were completed for high reach, mid range reach and low reach. A shelf location closest to the highest vertical free reach was used to measure high reach; mid level was set at or near the shoulder and the shelf for the lower reach was set at the MCP5 height while an individual was asked to reach as low as they possibly could at the side (lateral). The lowest possible shelf was 390 mm (15.3 in). This limit was set for safety reasons.

Three sets of reach trials were completed at three different positions – forward, laterally and at a 45 degree angle. There were no obstructions under the shelves because they projected out from the main part of the apparatus. The order of the trials was counterbalanced to control for fatigue but participants were told to stop and rest whenever they felt tired. Data is not reported here for the 45 degree reach.

Three-dimensional digital data has many advantages in reach studies. The distance between any pair of three-dimensional landmarks or reach coordinates can be computed. Moreover, projections of the coordinates to virtual planes at any orientation provide additional flexibility. As an example, reach limits can be computed from precise landmarks on the shoulder, parts of the mobility device, like the most leading edge (anterior most) or trailing edge (posterior most) of the person or device. Reaching abilities can also be projected onto planes inserted at any location in the reach envelope.

The uniform variables for forward reach in the standards assume that an individual is reaching to a plane that is at the anterior (forward) most point on the device or the body (e.g. toes) or set back from a counter edge (reach over obstruction). For side reach, the uniform variables assume that an individual is reaching to a plane at the extreme lateral (side) most point of the body or device or set back from a similar counter edge. A computational procedure was used to identify the locations where forward and side reaching abilities, as measured by the three dimensional reach envelope, intersect virtual planes at the anterior most point and the lateral most point. For lateral reach we also calculated reach to a second plane set 254 -610 mm (10 - 24 in.) back from the lateral most point (not reported here). For the purpose of this report, all reach limits were calculated to the acromion, a bony protuberance on the shoulder. 

Maneuvering clearances were measured while participants conducted standardized maneuvers inside a set of lightweight movable walls. The walls were gradually moved further apart until the maneuver could be completed without the participants moving the walls. Clearances were pre-measured on the floor of the test site using tape and marker and the locations of walls were recorded after each trial. Maneuvering trials included an L or 90 degree turn and a 360-degree turn within a confined space. The latter could be completed as a “K”-turn or a “U”-turn or any other maneuver as long as the participant wound up facing in the same direction as their starting position. Clearances were pre-measured on the floor of the test site using tape and marker.

In the L turn, the starting width of the clearance was the closest pre-measured clearance to the occupied width of the individual’s device (leaving no more than 50 mm of clearance to either side). In the 360 degree turn in a confined space, the starting clearance was an 1100 mm (43 in.) wide square space. Each participant was asked to complete the trial and, if a wall was moved in the course of the trial, the clearance was increased 50 mm and another trial completed until the participant was able to complete a trial without moving a section of wall. In the 360-degree turn in a confined space, two adjoining sections of wall were moved out as one unit along the diagonal so that the space stayed square in proportion. All trials were videotaped for later observation although the minimum clearance required was noted during the trials.