UWL: Activity Level Factors (2007)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To determine whether gait instability is involved in the higher energy cost of walking in healthy elderly subjects, and to determine whether greater gait instability is associated with greater energy expenditure to maintain balance while walking. 
Inclusion Criteria:
  • Healthy
  • Living independently
  • Went on country walks once a week, at least 9 months per year
  • Young sedentary subjects were healthy and had not previously engaged in any form of regular physical exercise
Exclusion Criteria:
  • Screened to eliminate subjects with medical problems that might affect gait, balance, or energy cost of walking
  • Score below 26 on the Mini Mental State Examination
  • Free of clinically significant orthopedic, neurological, cardiovascular, or respiratory problems
  • None of the participants were taking medications with known major effects on balance or gait, such as benzodiazepines, neuroleptics, and antidepressants
Description of Study Protocol:


Older subjects were recruited from associations that offer different activities for the elderly, including regular country walks, gymnastics, and cultural activities.

Design:  Case-Control Study

Blinding used (if applicable):  not applicable 

Intervention (if applicable):  not applicable 

Statistical Analysis

One-factor ANOVA used to determine differences in characteristics in descriptive characteristics among groups.  Two-factor ANOVA was used to determine the effects of age and speed of walking on mean VO2 and energy cost.  Linear regression analyses of VO2 vs the squared speed were performed on the data of each subject.  When global difference was identified, Tukey's post hoc analyses were performed.  When the assumption or the equality of variance was violated, an ANOVA (Kruskal-Wallis) for nonparametric values was used.  A Kruskal-Wallis test was used to identify differences in gait analysis parameters among the groups.  If the test showed significant differences, Mann-Whitney U tests were performed to compare 2 groups at a time.  Correlations between gait instability measures and age, physical activity score, energy cost of walking at preferred walking speed and compartment 2 of the Hoffman model were performed by using the Spearman correlation coefficient.

Data Collection Summary:

Timing of Measurements

Energy cost of walking and gait instability measured in all subjects and compared.  1 week later, subjects returned for measurements of basal metabolic rate and estimation of body composition.

Dependent Variables

  • Energy cost of walking and gait instability assessed by stride to stride changes in the stride time, walking on a treadmill at 6 different speeds with pressure-sensitive insoles
  • Preferred walking speed
  • Body composition measured through bioimpedance analysis
  • Physical activity estimated using a physical activity questionnaire for the elderly
  • Leg length measured between great trochanter and ground
  • Muscle function assessed using one-leg extension machine
  • Basal metabolic rate assessed through indirect calorimetry using standard protocol

Independent Variables

  • Age

Control Variables


Description of Actual Data Sample:

Initial N: 10 octogenarians (7 females, 3 males), 10 65-year olds (7 females, 3 males), 10 young controls (7 females, 3 males)

Attrition (final N): as above

Age:  mean age octogenarians:  81.6 +/- 3.3 years (range 77 - 86 years), mean age 65-year olds:  65.3 +/- 2.5 years (range 60 - 69 years), and mean age controls:  24.6 +/- 2.6 years (range 20 - 29 years).

Ethnicity: not mentioned

Other relevant demographics: see Results

Anthropometrics:  Groups were matched according to gender, height, leg length, body mass, lean body mass, percent body fat, and basal metabolic rate.

Location:  France


Summary of Results:



80 year olds

65 year olds

Young controls

Height (m) 1.61 +/- 0.1 1.62 +/- 0.1 1.64 +/- 0.07

Leg length (m)

0.89 +/- 0.05

0.84 +/- 0.06

0.85 +/- 0.04

Body mass (kg) 60 +/- 12.9 60.7 +/- 14.9 58.9 +/- 8.6
Lean body mass (kg) 44 +/- 10 46.2 +/- 12.5 45.4 +/- 8.8
Percent body fat (%) 26.4 +/- 6.9 24.2 +/- 6.6 23 +/- 7.1
BMR (ml/kg/min) 2.8 +/- 0.6 2.6 +/- 0.3 2.6 +/- 0.3
Standing oxygen update (ml/kg/min) 6.4 +/- 1.32 5.85 +/- 0.79 6.05 +/- 0.53
Physical activity score 12.63 +/- 4.54 18.93 +/- 6.3 --
Maximum voluntary isometric contraction (right, N) 221.7 +/- 99.2 265.4 +/- 68.3 353.2 +/- 102.4

Maximum voluntary isometric contraction (left, N)

186.4 +/- 75.4

244.3 +/- 60.9

326.7 +/- 79.4

Other Findings

The energy cost of walking was higher for the 80 year olds than for the 25 year olds across the different walking speeds (P < 0.05).

Stride time variability at preferred walking speed was significantly greater in 80 year olds (2.31 +/- 0.68%) and 65 year olds (1.93 +/- 0.39%) compared with 25 year olds (1.40 +/- 0.30%, P < 0.05).

There was no significant correlation between gait instability and energy cost of walking at preferred walking speed.

These findings demonstrated greater energy expenditure in healthy elderly people while walking and increased gait instability, however, no relationship was noted between these 2 variables. 

Author Conclusion:
In summary, this study shows that both energy cost of level walking and stride time variability are greater in octogenarians than in young adults.  However, no relationship was found between these 2 variables, suggesting that gait instability is not the main explanation of the higher energy cost of walking in the elderly.  Differences in compartment 3, which represents the energy expenditure associated with walking movements, and in the maximum voluntary isometric contraction of the knee extensors instead appear to be responsible for the higher energy cost of walking in the healthy elderly.  Future research should examine the bioomechanical and neuromuscular factors accounting for the differences in walking economy between healthy elderly and young subjects.
Funding Source:
University/Hospital: Hopital Arnaud de Villeneuve, Hopital Gui de Chauliac (both France)
Reviewer Comments:
Small number of subjects in groups.  Measurements made 1 week apart.  Authors note that the subjects may not be representative of the general elderly population.
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) N/A
  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) N/A
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? ???
  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? ???
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.) Yes
  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.) Yes
  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? 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%.) 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? N/A
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? Yes
  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? N/A
  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? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? N/A
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? N/A
  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? N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? ???
  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? N/A
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? ???
  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? No
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