Independent Wheelchair Transfers in the Built Environment: How Transfer Setup Impacts Performance Phase 2: Final Report

Addendum E: Comparison of participants tested at the National Disabled Veterans Winter Sports Clinic (NDVWSC) compared to the participants tested at the Human Engineering Research Laboratories and Hiram G. Andrews Center

At the time this addendum was composed, there were 31 participants enrolled in the phase 2 study at HERL (27 men and 4 women).  This group of subjects was compared to all the subjects who were tested at the NDVWSC (22 men and 9 women).  The general subject demographics broken down by group are shown in Tables E1-E3. 

Table E1: Subject demographics for both HERL and NDVWSC study participants. Mean and standard deviation of the samples are shown.

Table E2: Type of wheelchairs used by HERL and NDVWSC study participants

Table E3: Disability types among the HERL and NDVWSC study participants

For protocols A, B and C (same set up as described in the report) a comparison of the 5th, 25th, 50th, 75th, and 95th percentiles was calculated and shown below.

Protocol A Heights Obtained

The highest and lowest obtained transfers were compared for the participants that were tested at HERL (n=31) and the participants that were tested at the NDVSWC. The transfer heights obtained in protocol A for both sample groups can be seen in tables E4 and E5.

Table E4. Percentiles for the Lowest Attainable Transfer Heights Protocol A
Data shown in inches

Table E4 Alternative Text Description: This table shows the attainable height percentiles for Protocol A minimum height transfers. Participants are divided into three groups in column one: participants tested at HERL, participants tested at the NDVWSC, and all participants. Columns two through six show the transfer heights for 5th, 25th, 50th, 75th, and 95th for each subset of participants. HERL participants tended to be able to transfer lower than NDVWSC participants. They attained lower heights in the 25th and 50th percentiles. The 5th, 75th, and 95th percentiles are equal for all groups.

Table E5. Percentiles for the Highest Attainable Transfer Heights Protocol A
Data shown in inches

For the minimum height transfer, the participants tested at HERL transferred about 1.4" lower on average than the participants tested at the NDVWSC.  The upper 95th percentile transfer heights were 3" higher for the NDVWSC than the HERL group for the maximum height transfer.

Protocol B Heights Obtained

The data for each of the two groups can be seen in tables E6 and E7. Again for the minimum height protocol HERL participants transferred lower on average than the NDVWSC participants. For the maximum height transfer the participants tested at HERL transferred slightly higher than the participants tested at the NDVWSC based on all calculated percentiles.

Table E6. Percentiles for the Lowest Attainable Transfer Heights Protocol B
Data shown in inches

Table E7. Percentiles for the Highest Attainable Transfer Heights Protocol B
Data shown in inches

Protocol C Heights Obtained

Like the two previous protocols the HERL participants transferred lower on average compared to the NDVWSC participants. For the maximum height transfers HERL's percentile heights were slightly higher for the 25th and 75th percentiles than the NDVWSC heights. These results can be seen in tables E8 and E9 respectively.

Table E8. Percentiles for the Lowest Attainable Transfer Heights Protocol C
Data shown in inches

Table E9. Percentiles for the Highest Attainable Transfer Heights Protocol C
Data shown in inches

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 E10, 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 10) showed no statistically significant differences between the two groups for transfer performance.  This result supports that the veterans who participate in these events are not very different from the subjects that we recruit at HERL from the general community. 

Table E10:  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 heights attained between both subject populations. Height data are shown in inches. No significant difference was found between the subjects.