- Click here for explanation of classification scheme.

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. 

• 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

• 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

Recruitment

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.

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

 

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

 

 

	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. 

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.

University/Hospital:

Hopital Arnaud de Villeneuve, Hopital Gui de Chauliac (both France)

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.