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SCI: Physical Activity (2007)


Cooper RA, Fitzgerald SG, Boninger ML, Prins K, Rentschler AJ, Arva J, O'Connor TJ. Evaluation of a pushrim-activated, power-assisted wheelchair. Arch Phys Med Rehabil. 2001;82:702-708.

PubMed ID: 11346854
Study Design:
Randomized Crossover Trial
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To determine the performance of the PAPAW with appropriate American National Standards Institute-Rehabilitation Engineering and Assistive Technology Society of North America (ANSI-RESNA) standards, to compare metabolic energy demands for the pushrim-activated, power-assisted wheelchair (PAPAW) with subjects' manual wheelchairs, and to compare performance of selected activities of daily living (ADLs) with the PAPAW with subjects' personal wheelchairs.
Inclusion Criteria:
None noted by author.
Exclusion Criteria:
None noted by author.
Description of Study Protocol:


Subjects were recruited from the Human Engineering Research Laboratories, VA Rehabilitation Research & Development Center, VA Pittsburgh Healthcare System, University of Pittsburgh, Pittsburgh, PA


This study was perfromed in three phases, the second and third of which were repeated-measures designs.

Blinding used (if applicable):  Not applicable

Intervention (if applicable)

Phase 1: Wheelchair standards testing which involved compliance testing, with a test dummy, in accordance with the wheelchair standards of the ANSI-RESNA.

Phase 2: Metabolic energy consumption testing - at 2 speeds and 3 resistance levels - in the subject's manual wheelchair and the PAPAW.

Phase 3: Evaluation of ability to perform ADLs and ergonomics of the PAPAW compared with the subjects personal wheelchair.

Statistical Analysis 

  • Metabolic energy consumption was analyzed using paired t tests for normal distribution or Wilcoxon rank-sum test for data not normally distributed.  Significance was set a p < 0.05. A mixed analysis of variance (ANOVA) was used to determine if differences existed between the 2 types of chairs and 5 trials (2 speeds, 3 resistance levels).
  • ADLs were analyzed using a one-way ANOVA to identify differences in ratings for ease and comfort of tasks, and to identify differences in physical strain. A significance of p < 0.05 was used. A multiple comparison least significant difference post hoc test was applied to identify significant differences among the groups (p = 0.05). A paired 1-tailed t test was used to identify differences for all variables for the car transfer. Paired t tests were also used to identify differences in ratings, time period, and physical strain among ADL tasks performed during trial 1 and 3 with the PAPAW (p < 0.05). Repeated measures ANOVA was used to identify task completion time differences at the subject level among the groups (p < 0.05). Differences in the amount of strokes used for propulsion with each wheelchair were analyzed with Kruskal-Wallis test (p < 0.05).
Data Collection Summary:

Timing of Measurements

Phase 1: Two Quickie GP wheelchairs were tested using ANSI-RESNA standards in the order prescribed by the standards.

Phase 2: In random order, subjects propelled their manual wheelchairs on a computer-controlled wheelchair dynamometer. 5 minutes were allowed to acclimate to the experimental set-up and each subject was given a 5-minute break between each trial.

Phase 3: All subjects propelled over a standardized ADLs course 3 times. The number of propulsion strokes were counted by the investigator and recorded.

Dependent Variables

  • Wheelchair standards testing including (1) static stability, (2) dynamic stability, (3) effectiveness of brakes, (4) energy consumption, (5) overall mass, dimensions, (6) speed, acceleration, (7) seating and wheel dimensions, (8) static, impact, fatigue strength, (9) obstacle climbing, and (10) environmental testing.
  • Metabolic energy consumption by oxygen consumption (VO2mL/kg X min, VO2mL/min and ventilation (VEL/min)
  • ADLs evaluation by subjects' ratings, heart rate (HR), completion time, and stroke frequency  

Independent Variables

  • PAPAW and the subject's manual wheelchair

Control Variables

 none noted

Description of Actual Data Sample:

Initial N:

  • Phase 2: 10 manual wheelchair users (4 women, 6 men)
  • Phase 3: 10 manual wheelchair users (6 men, 4 women)

Attrition (final N):

  • Phase 2: 10 subjects
  • Phase 3: 10 subjects


  • Phase 2: 35 ± 10.7 SD years
  • Phase 3: 45.2 ± 7.1 SD years


  • Phase 2: 90% Caucasian
  • Phase 3: not noted

Other relevant demographics:

  • Phase 2: Mean length of time post SCI 13 ± 10.4 SD years. 9 subjects had a T2-12 injury, 1 had multiple sclerosis (MS)
  • Phase 3: 8 subjects with thoracic SCI, 1 subject with lumbar SCI, 1 subject with MS, use of manual wheelchair 17 ± 6.3 SD years.

Anthropometrics:  Crossover trial


A rehabilitation engineering center within a Veterans Affairs medical center

Summary of Results:

 Results of metabolic testing with the PAPAW and subject's personal wheelchair



Mean ± SD


  Ventilation (L/min)

Mean ± SD

 Vo2 (mL/kg ·min)

Mean ± SD

  Heart Rate (bpm)

Mean ± SD


Personal PAPAW Personal PAPAW Personal PAPAW Personal PAPAW

1.8m/s, 25W





 42.7±13.5  12.7±3.1



 138±27  121±26
1.8m/s, 30W





 39.8±9.0  15.3±3.5






0.9m/s, 10W  515±139












0.9m/s, 12W  565±179









 110±21  91±34
0.9m/s, 14W  570±136



 36.9±8.4  40.1±13.6  8.4±2.0



 101±42  96±36

 With the PAPAW, the subject had a significantly lower oxygen consumption and heart rate when compared with a manual wheelchair at different speeds

Other Findings

Phase 1: the PAPAW was found to be inc ompliance with wheelchair standards

Phase 3: the PAPAW had a significantly higher ergonomic evalutaion (p<.01) than the subject's personal wheelchair. The ratings of the car transfer between the PAPAW and the subject's personal wheelchair showed a significant difference in the task of taking the wheels off (p<.001) and putting the wheels back on (p=.001), with the PAPAW receiving lower ratings.

Author Conclusion:
The tested PAPAW is compliant with wheelchair standards, reduced the energy demand placed on the user during propulsion, and subjects rated its ergonomics favorably when compared with their personal wheelchairs. PAPAWs may provide manual wheelchair users with a less stressful means of mobility with few adaptations to the vehicle or home environment.
Funding Source:
Foundation associated with industry:
Reviewer Comments:
The abstract indicated that 11 subjects participated in the trial but only 4 women and 6 men were identified in each of the trials.
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? No
  2.2. Were criteria applied equally to all study groups? ???
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) No
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? Yes
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? Yes
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? Yes
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? ???
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? Yes
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? No
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? No
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes