This Academy member benefit temporarily has been made public to allow all practitioners access to content that may assist in patient care during the national pandemic response. Click here for information on joining the Academy. 

SCI: Physical Activity (2007)

Citation:
Mukherjee G, Bhowik P, Samanta A. Energy cost of manual wheelchair propulsion at different speeds. International J Rehab Research 2002;25:71-75. PubMed ID: 11953719
 
Study Design:
Non-Randomized Crossover Trial
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To measure the degree of physical stress by the set of physiological parameters caused by the propulsion of MWCs at different speeds.  It is also aimed to evaluate and compare these physiological parameters with respect to their effectiveness in reflecting the true stress at different speeds and consequently to find out relative economies of propulsion speeds.
Inclusion Criteria:
  • Regular users of MWCs for past 6 years
  • Had good strength and control of upper limbs, trunk and abdominal muscles
  • Were without any medical complications
Exclusion Criteria:
Not noted by author.
Description of Study Protocol:

Recruitment

Volunteers - method not described.

Design

  • Prior to testing all participants completed an orientation session to familiarize themselves with the test procedures.
  • After a rest of 15 minutes, the participants propelled the MWC around a track for three separate sessions with an intrval of an hour.
  • First they propelled the MWC at whatever sustained speed they found comfortable (FCS), continuously for 5 minutes; then at low speed (based on 40-50% of FCS that were around 20-30m/min); then at fast speed (approximately 50% more than the FCS.  The ambulatory data (speed, oxygen uptake, and HR were collected immediately after the cessation of assigned work.

Blinding used (if applicable):  Not applicable

Intervention (if applicable):   Not applicable

Statistical Analysis

Mean and SD were collected for all variables. Polynomials of second degree were fitted to the data for the relationship between speed and physiologic measures.  The coefficient of determination, R2 was calculated in each case. Physiological response at different speeds was compared using the 2-sampple t test.

Data Collection Summary:

Timing of Measurements

Data was collected after a 15 minute rest period at the beginning of the study.  Three separate sessions were completed with an interval of an hour. Each test lasted 5 minutes and data was collected immediately after cessation of each test.

Dependent Variables

  • Speed (m/min)
  • Oxygen uptake (l/min)
  • Heart rate (HR) (bpm)
  • Energy cost per unit time (Oxygen consumption (ml/kg/min)
  • Energy cost per unit distance (ml/kg/m)
  • Physiological cost index (PCI) calculated by subtracting resting HR from ambulatory HR and dividing by propulsion sped.

Independent Variables

  • Propulsion of maunal wheelchair (MW) at different speeds

Control Variables

None noted by author

Description of Actual Data Sample:

Initial N:

15 males

Age: 34.26 ± 8.99 years

Ethnicity: Asian Indians

Other relevant demographics:

  • Height 153.26 ± 5.75 cm
  • Weight 45.8 ± 8.8 kg
  • Paraplegia (below tenth thoracic vertebra)and poliomyelitis population

Anthropometrics:  crossover trial

Location: India

Summary of Results:

 Energetics of manual wheelchair propulsion at different speeds

Variables

               Graded Speed

                   Mean  ± SD

  Slow Freely Chosen Fast
Speed (m/min) 24.6 ± 2.79 56.8 ± 8.73 72.33 ± 4.98

Heart Rate (bpm)

110.53 ± 5.30

 127.13 ± 8.71

 158.46 ± 7.64

PCI (bpm)

 1.33 ± 0.22

 0.84 ± 0.11

 1.09 ± 0.07

O2 consumption (ml/kg/min) 9.52 ± 1.14 14.02 ± 2.94  16.36 ± 3.54
O2 cost (ml/kg/m) 0.40 ± 0.03 0.24 ± 0.03  0.22 ± 0.04

The HR response of MWC propulsion at 3 different speeds increased as speed increased. PCI, the value at low speed indicates poor economy and high physiological cost.  Oxygen consumption increased with increase in speed, however oxygen consumption did not increase at the same rate as speed.  This is indicative that HR increased but oxygen consumption did not from FCS to high speed  in the trials.  This may be due to the static work that increases HR and at a lower speed may be less effective.

Other Findings

 HR may provide the most comprehensive and dynamic evaluation of cardiovascular strain imposed by workloads at varying intensity.

Author Conclusion:
During MWC propulsion, the physiological demand changes with propulsion speed, however, MWC propulsion is safe and energy efficient is propelled slower than the Freely chosen speed (FCS). Energy cost is most economic at FCS.
Funding Source:
Reviewer Comments:
A careful standardization of confounding variables was not possible as in laboratory studies. Some unknown covariates could have existed.
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? 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? N/A
  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? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  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")? N/A
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%.) 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? Yes
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)? 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? 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