SCI: Physical Activity (2007)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To determine the energy cost of wheelchair propulsion (WCP) in people with spinal cord injury (SCI), comparing ultralight wheelchairs (UWCs) with standard wheelchairs (SWCs), people with different levels of injury and changes over a 20-minute trial.
Inclusion Criteria:
  • Complete injury as defined in the international standards of the American Spinal Injury Association (ASIA) or sparing of only light touch
  • Had a stable spine at the time of testing and were free from any rigid external trunk or neck support
  • Were able to propel a manual WC for at least 20 minutes at a self-selected speed
  • Were in good health except for the sequelae of the SCI.
Exclusion Criteria:
Subjects with C5 tetraplegia were not included because use of manual WCP is typically not a goal for these patients.
Description of Study Protocol:


Not described.


  • Each subject performed two trials of WCP: One in an SWC and one in a UWC
  • The order of testing was randomized for each subject and the two tests were performed no less than 24 hours and no more than 72 hours apart
  • Subjects propelled each WC for 20 minutes around a level outdoor track (60.5m in circumference), at self-selected speeds, while data was collected at four pre-determined intervals  
  • Test equipment was fitted to each subject and he or she was given three to five minutes to become familiar with breathing into the mouthpiece and propelling while wearing the apparatus
  • After a three-minute rest, baseline resting data for oxygen uptake were recorded for two minutes.


Two trials of WCP: One in an SWC and one in a UWC.

Statistical Analysis

  • Mean and SD were calculated for descriptive data and the energy cost variables
  • Speed, distance traveled and oxygen cost were compared by wheelchair, group and over time (four data collection periods) using a mixed-design ANOVA with one between-group factor (the four groups) and two within-group factors (WC and time)
  • Scheffe post-hoc tests were used to determine significant comparisons
  • The level of significance was lowered from 0.05 to 0.0167 using Bonferroni correction for three independent variables.
Data Collection Summary:

Timing of Measurements

  • Expired air samples were collected without interrupting propulsion for two minutes at Minutes Three through Five and for one minute at Minutes Nine through 10, 14 through 15 and 19 through 20.
  • The distance traveled was recorded during each period: Total distance traveled during 20 minutes or the maximum time pushed was determined by counting the number of laps completed.

Dependent Variables

  • Speed (in meters per minute)
  • Distance traveled (in meters)
  • Oxygen cost per distance traveled (VO2ml per kg per m).

Independent Variables

  • Type of wheelchair (UWC and SWC)
  • Group (C6, C7-8, T2-8, T10-L1) as well as tetraplegia and paraplegia
  • Over time (minutes).

Control Variables

None noted.
Description of Actual Data Sample:
  • Initial N: 74 subjects; 69 were men, five were women
  • Attrition (final N): 74
  • Age: 26.2±7.14;, range, 17 to 50 years
  • Ethnicity: Not noted by author.

Other Relevant Demographics

  • All subjects had lesions at neurological level C6 or below; 44 with paraplegia and 30 with tetraplegia
  • Time from onset of SCI to testing averaged 5.1 months for all subjects.


14 subjects had lesions at C6, 16 subjects had lesions at C7-8, 19 subjects had lesions at T10-L1.


Pathokinesiology Laboratory, Rancho Los Amigos Medical Center.

Summary of Results:

Comparison by Wheelchair, Total Distance Traveled




T2-8 T10-L1 Tetraplegia Paraglegia
No. of subjects per group 14 16 25 19 30 44

SWC Mean ±SD

784.75±155.15 985.66±222.30 1,333.64a±265.18 1,439.50b±218.29 891.90c±216.21 1,379.35d±249.02

UWC Mean ±SD




1,557.72±237.4 958.65±256.75 1,534.86±275.55

a: Difference between wheelchairs, T2-8, P<0.0000
b: Difference between wheelchairs, T100-L1, P=0.0080
c: Difference between wheelchairs, subjects with tetraplegia, P=0.0182
d: Difference between wheelchairs, subjects with paraplegia, P<0.000.

 Comparison by Wheelchair, Mean Speed
(m per minute)




T2-8 T10-L1 Tetraplegia Paraglegia
No. of subjects per group 14 16 25 19 30 44

SWC Mean ±SD

40.38±8.15 50.57±11.25 67.85a±13.33 72.52b±10.74 45.81c±11.13 69.87d±12.47

UWC Mean ±SD



77.85±15.94 80.91±11.62 49.00±213.37 79.17±14.28

a: Difference between wheelchairs, T2-8, P=0.0000
b: Difference between wheelchairs, T10-L1, P=0.0025
c: Difference between wheelchairs, subjects with tetraplegia, P=0.0185
d: Difference between wheelchairs, subjects with paraplegia, P<0.000.

Comparison by Wheelchair, Mean Oxygen Cost
(VO2, in ml per kg per m) 




T2-8 T10-L1 Tetraplegia Paraglegia
No. of subjects per group 14 16 25 19 30 44

SWC Mean ±SD

0.19±0.05 0.16±0.03 0.16a±0.03 0.15b±0.03 0.17±0.04 0.16c±0.02

UWC Mean ±SD



0.13±0.02 0.13±0.02 0.16±0.05 0.13±0.02

a: Difference between wheelchairs, T2-8, P<0.0000
b: Difference between wheelchairs, T10-L1, P=0.009
c: Difference between wheelchairs, subjects with paraplgia, P<0.0000.

Author Conclusion:
  • The use of UWCs instead of SWCs for people with paraplegia is supported by the increased speed, increased distance traveled, and decreased oxygen cost achieved
  • The use of UWCs instead of SWCs for people with C6 and C7-8 tetraplegia is also supported, however the changes were not as great as for the subjects with paraplegia
  • People with tetraplegia have less efficient WCP than do people with parplegia
  • All subjects with tetraplegia were extremely inefficient in WCP and were limited by weakness that disallowed any efficient method of manual propulsion.
Funding Source:
Everest and Jennings
Reviewer Comments:
  • Subjects were more familiar with the SWC compared to the UWC despite practice trials with the UWC
  • Some subjects had never propelled a UWC before the study
  • Seat-to-wheel position, wheel camber and other factors that might influence WC efficiency were not adjusted for each subject in the UWC and were not possible for the SWC
  • Many more UWCs are now available which may alter results especially for subjects with tetraplegia
  • Study was carried out somewhat early in the period following injury
  • Most subjects were relatively untrained, which would have affected outcome
  • Use of the Bonferroni correction increases the possiblity of Type II error, while decreasing the possiblity of Type I error
  • Small sample size of the C6 and C7-8 tetraplegia necessitated combining them to increase the statistical power which may have masked differences in the groups
  • Two subjects failed to complete the final data collection period: One subject with C6 tetraplegia in the UWC and one subject with T2-8 paraplegia in the SWC.
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) 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? 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? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  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? N/A
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? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  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? Yes
  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)? N/A
  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