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SCI: Physical Activity (2007)


Algood SD, Cooper RA, Fitzgerald SG, Cooper R, Boninger ML. Impact of a pushrim-activated power-assisted wheelchair on the metabolic demands, stroke frequency, and range of motion among subjects with tetraplegia. Arch Phys Med Rehabil 2004;85:1865-1871.

PubMed ID: 15520983
Study Design:
Time Study
C - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To determine differences in metabolic demands, stroke frequency, and upper-extremity joint range of motion (ROM) during pushrim-activated power-assisted wheelchair (PAPAW) propulsion and traditional manual wheelchair propulsion and traditional manual wheelchair propulsion among subjects with tetraplegia.
Inclusion Criteria:
Participants had to be between the ages of 18 and 65 years, full-time manual wheelchair users (MWU) for at least one year with tetraplegia, free from pressure ulcers and shoulder pain, and have no history of cardiopulmonary disease.
Exclusion Criteria:
None noted by author.
Description of Study Protocol:


Participants were recruited through the Human Engineering Research Laboratories' registry through either letter or by telephone.


  • Participants were not to eat for 2 hours before testing.  For all testing the participants propelled both their own manual wheelchair and a PAPAW on a computer-controlled wheelchair dynamometer. 
  • Participants were asked to maintain a speed of 0.9m/s through 3 different dynamometer resistance conditions (slight, moderate, high) for both the PAPAW and their own manual wheelchair.  The order in which the wheelchairs were presented to each participant was randomized.  The resistance conditions simulated trials of propelling on a flat tiled floor (slight: 0.9m/s, 10W), a flat carpet (moderate: 0.9m/s, 12W), and uphill (high:0.9m/s, 14W).  Each of the 6 propulsion trials was for 3 minutes.
  • After the testing, the steady state of each participant was confirmed by an investigator who visually observed that metabolic and heart rate values had reached a plateau after 2.5 minutes. Participants were given 5 mintues to get acclimated to the test setup and were provided with a 5-minute rest between each trial. The participants were also provided with a visual display of their real-time speed throughout the propulsion trials.
  • The PAPAW was a Yamaha JWII mounted to a Quickie 2 folding frame manual wheelchair, which was selected and adjusted to the particpant's own wheelchair's current seat dimensions.

Two Optotrak 3D 3020 motion analysis cameras were used to collect the positioning data of infrared markers palced on both sides of the participant's body. This set position was taken to ensure that similar wheelchair setup between the participant's own manual wheelchair and the PAPAW's.

Blinding used (if applicable): Not applicable

Intervention (if applicable):  Not applicable

Statistical Analysis

  • Descriptive analyses were performed for all variables, and histograms were evaluated for normal ditributions.
  • Paired sample t-tests were used to compare the means of data that were normally distributed and Wilcoxon ranksum tests were perfromed on data that were not normally distributed. 
  • A mixed-model analysis of variance (ANOVA) was used to determine whether differences existed between the 2 types of chairs and the 3 resistance conditions. 
  • Power analyses were computed and revealed that for all variables, 15 participants were needed to provide at least 75% power in the study.
Data Collection Summary:

Timing of Measurements

For each trial four minutes of physiologic data were collected: 1 minute resting and 3 minutes of propulsion. Steady-state oxygen consumption (VO2) and ventilation rate (V2) were acquired using an Aerograph VO2000 metabolic cart which was calibrated before each testing session. Each participant's nose was clamped to prevent air loss from the system.  Heart rate data was collected by a Polar T31 wireless heart rate monitor and heart rate was continuously monitored. 

Dependent Variables

  • Oxygen consumption (VO2)
  • Ventilation (Ve)
  • Heart rate (beats per minute)
  • Stroke frequency
  • Range of motion (ROM) angles for the shoulder, wrist joints, elbow

Independent Variables

  • Mean velocities at the three resistance levels (slight, moderate, high)

Control Variables

  • None noted
Description of Actual Data Sample:

Initial N: 15 full-time MUWs with tetraplegia (cervical-level SCI); 12 men/3 women

Attrition (final N):  15 participants

Age: 37.3 ± 7.3 years (range 27 - 52 years)

Ethnicity: Not noted by author.

Other relevant demographics: Height 180.0 ± 1.4 cm (range152 - 193 cm)


Location: A biomechanics laboratory within a Veterans Affairs medical center

Summary of Results:



Mean velocity at 0.9m/s 10W


Mean velocity at 0.9m/s 10W

Mean velocity at 0.9m/s, 12W


Mean velocity at 0.9m/s, 12W

Mean velocity at 0.9m/s, 14 W


Mean velocity at 0.9m/s, 14 W

   Personal PAPAW  Personal  PAPAW  Personal  PAPAW
VO2 (ml/min)  625 ± 316 415 ± 204*

 664 ± 261

415 ± 164*  855 ± 389 485  ± 199*
Ve (L/min)

 19.1 ± 9.0

11.0 ± 9.0*

 20.2  ± 9.2

11.1 ±  3.5*

 27.4 ± 11.9

12.5 ± 4.0*
VO2 (mL·kg–¹·min–¹)

 8.0 ± 4.0

 5.1 ± 2.4*

 8.6 ±  3.0

 5.3 ± 1.8*

 10.9 ± 4.6

 6.2 ± 2.1*
Heart rate (bpm)  102 ± 23  91 ±  32  99 ± 20  90 ± 33  129 ± 30  93 ± 14*
Mean stroke frequency  .80 ± .14  .64 ± .11*  .82 ± .13  .63 ± .11*  .74 ± .17  .65 ± .13*

 Values are mean ± SD

* p < 0.05

For oxygen consumption and ventilation, a significant difference was noted between the two wheelchairs. Mean heart rate was significantly reduced when using the PAPAW during the high resistance trial. Results of the mixed ANOVA showed that the PAPAW was responsible for the observed changes in all dependent variables.  Stroke frequency was significantly reduced for participants for the slight (p = 0.001) and moderate (p = 0.001) resistances but there were no significant differences between the 2 chairs when resistance was at the highest setting (p = 0.078).

Other Findings

For ROM during the slight resistance, paired sample t-tests showed significantly lower ROM when using the PAPAW for shoulder flexion and extension (p=0.003), internal and external rotation (p = 0.032), horizontal flexion and extention (p=0.028), and wrist ulner and radial deviation (p=0.028).

At moderate resistance, a significant decrease in ROM was observed for shoulder flexion and extension (p=0.005), internal and external rotation (p=0.002), horizontal flexion and extension (p=0.043), as well as forearm supination and pronation (p=0.008) and ulnar and radial deviation (p =   0.014).

At the highest resistance, there were significant decreases in overall ROM when using the PAPAW for all joint movements except for shoulder abduction and adduction.

Author Conclusion:
In participants with tetraplegia, PAPAW's reduce the energy demands, stroke frequency, and overall joint ROM when compared with traditional manual wheelchair propulsion.
Funding Source:
Government: NIDRR, US Dept. of Edu, US Dept. US Dept. of Veterans Affairs
Reviewer Comments:

The relatively short propulsion trials during the first phase might not allow all participants to reach steady state. Some participants were fatiguing when using their own manual wheelchairs after 3 mintues of propulsion.

Sample size was small, there was a high variablity of the metabolic data and marker dropout during the kinematic testing.

One subject was unable to complete a high resistance trial when using a manual wheelchair due to fatigue.

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? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  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) N/A
  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? N/A
  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%.) Yes
  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? ???
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  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? N/A
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? ???
  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? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
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