The Impact of Transfer Setup on the Performance of Independent Transfers: Phase I Final Report

ADDENDUM TO PHASE I FINAL REPORT: Points of Clarification

Further clarification on four participants who were admitted into the study, but were not able to attain any transfers in any of the protocols.

These four participants told us that they could independently transfer in their usual environments.  Thus they met the requirement for inclusion into this study (see inclusion and exclusion criteria for the study listed on Page 5, Number 2 which states that the person is be able to independently transfer to/from a wheeled mobility device with or without a transfer board).  This criteria was based on self-reported information to the study investigators.  When it came time for them to perform a transfer to the station in this study they could not do it because they were hindered by the constraints imposed by the transfer station design.  More specifically, these subjects could not position themselves and/or their mobility devices in the way that they would normally do to perform an independent transfer because they were hindered by the foot constraints that were fixed on the floor along the sides and in front of the transfer platform.  These subjects were included in the numbers of subjects who 'unattained' the transfers for each of the protocols.  This was done because these subjects would not be able to do the same kinds of transfers in the real world (e.g. when faced with a situation where there was a similar type of obstacle on the floor that they needed to transfer over). 

More information about how these four participants were handled in the analysis. 

These four subjects were grouped together with the other subjects who attempted each protocol but were unable to attain a successful transfer similarly due to the physical challenges of the station design.  The data from all these subjects who attempted but could not attain a successful transfer were included in the calculations for the overall percentages of subjects who transferred to certain heights, gaps, etc. under each protocol.  More specifically their data were included in Table 4, Table 5, Table 6, Table 7, Table 8, Table 9, and Table 13.  This was done so as not to skew the results in favor of those who could complete successful transfers.  Their data were not included in Figure 9, Figure 10, Figure 11, Figure 12, and Figure 13 which only contains data from participants that were successful with the transfers in each protocol. 

Clarification on number of subjects included in the “Adjustable Height” protocol analysis (Page 17 and (Page 20).

In addition to the four subjects who couldn't do any transfer, there was one subject who couldn't do any transfers in this protocol and one subject who could do some of the transfers in this protocol.  The Adjustable Height protocol included two types of transfers, a transfer to a higher height and a transfer to a lower height relative to the mobility device's seat to floor height. One subject could not transfer higher or lower than their device's seat to floor height.  This is the male subject who is described in the text as one of two additional subjects who couldn't attain the Adjustable Height transfer.  Another person, the female subject described in the text, could transfer lower but not higher than her device's seat to floor height. 

Clarification of references to some study participants as “wheelchair athletes”

It's important to be aware that while the National Veterans Wheelchair Games (NVWG) is a competitive event, it is mainly promoted as a recreational activity that veterans from all fitness levels can participate in.  Many of the events range from high intensity (e.g. basketball, rugby, handcycling) to low intensity (nine-ball, archery, air gun, table tennis, etc.) activities.  The National Disabled Winter Sports Clinic (NDVWSC) is a non-competitive event where recreation is the primary focus and a wide range of activities are offered from downhill skiing to snowmobiling. 

In the report, we did not specifically reference all the other studies that have collected activity levels from community dwelling 'non-athletic' wheelchair users.  A summary of the results of these studies are shown in Table A1 below.  While the mean distance traveled and average speed per day was slightly higher for NVWG participants using manual wheelchairs, the daily moving time (which is more reflective of general activity level) was very similar, if not lower than the other studies conducted among adult community dwelling manual wheelchair users.   However, there is no way to infer from the activity levels that higher activity level is linked to better transfer or transfer skills or vice versa.  In our experience, we have found that being an 'athlete' or a more active wheelchair user doesn’t necessary mean you will be better at performing transfer activities.

Table A1: Comparison of wheelchair activity across four studies from the scientific literature

Key:  NVWG = National Veterans Wheelchair Games; SCI = Spinal Cord Injury; NR = Not Reported in Study

Using the more current data collected for Phase 2 of subject testing in our muti-year study on transfer, we compared the actual transfer performance of the 31 veterans who were tested at the recent 2014 NDVWSC to the first 31 subjects recruited and tested in the study at HERL.   There were 27 men and 4 women tested at HERL and 21 men and 9 women tested at the NDVWSC.  The general subject demographics broken down by group are shown in Tables A2-A4.          

Table A2: Subject demographics for both HERL and NDVWSC study participants. Mean and standard deviation of the samples are shown.

Table A3: Type of wheelchairs used by HERL and NDVWSC study participants

                    Table A4: Disability types among the HERL and NDVWSC study participants

We compared the two groups for transfer heights to/from the wheelchair to a level platform with and without grab bars and also evaluated their maximum and minimum transfers heights to the platform for each grab bar condition.  As can be seen from the results in Table A5, the HERL and NDVWSC study participants attained similar transfer heights for all parts of the protocol.  An independent t-test comparison of these results (p-values shown in Table 5) showed no statistically significant differences between the two groups for transfer performance.  This result further supports that the veterans who participate in these events and that have been included in our studies are not very different from the subjects that we recruit at HERL from the general community. 

Table A5:  Comparison of transfer performance in Phase 2 of the multi-year study on transfers between wheelchair users tested at HERL and veterans tested at the NDVWC

Clarification on how the wheeled mobility device seat height was measured

Wheelchair measurements were completed without the person seated in their wheelchair.  The device seat to floor height was measured as the linear distance between the front of the seat, center-line point on top of the cushion (if present) and the floor (Figure 1A left).  This location was chosen to account for any hammocking, wear or compression of the seat upholstery and/or cushion.  However, for the setup of the baseline level transfer (when the person and mobility device were in a position next to platform ready to transfer), if there was a noticeable difference (one inch or more) between the occupied seat-to-floor height at the same center-line point at the front of the seat (plus cushion if present) ( Figure 1A right) and the height of the platform which was initially set based on the unoccupied seat to floor height, we adjusted the platform to match the occupied seat-to-floor height and this new measurement replaced the unoccupied measurement in the data set. 

Figure 1A:  Seat height measurements in an unoccupied (20.5" seat to floor height) and occupied wheelchair (19.5" seat to floor height).

http://herl.pitt.edu/ab/  (MS Word version)

Reference List

1. Tolerico ML, Ding D, Cooper RA, Spaeth DM, Fitzgerald SG, Cooper R, Kelleher A, and Boninger ML. Assessing the Mobility Characteristics and Activity Levels of Manual Wheelchair Users in Two Real World Environments. Journal of Rehabiliation Research and Development 44(4), 573-580. 2007.

2. Oyster ML, Karmarkar AM, Patrick M, Read MS, Nicolini L and Boninger ML. Investigation of factors associated with manual wheelchair mobility in persons with spinal cord injury. Arch Phys Med Rehabil 92: 484-490, 2011.

3. Sonenblum SE, Sprigle S and Lopez RA. Manual wheelchair use: bouts of mobility in everyday life. Rehabil Res Pract 2012: 753165, 2012.

4. Levy CE, Buman MP, Chow JW, Tillman MD, Fournier KA and Giacobbi P, Jr. Use of power assist wheels results in increased distance traveled compared with conventional manual wheeling. Am J Phys Med Rehabil 89: 625-634, 2010.