Comparison between an indoor and an outdoor 6-minute walk test among individuals with chronic obstructive pulmonary disease

OBJECTIVES: To investigate the feasibility of an outdoor 6-minute walk test (6MWT) as a measure of functional status among individuals with chronic obstructive pulmonary disease (COPD), and to examine the relationship between performance on an indoor and an outdoor 6MWT. DESIGN: An experimental, repeated-measures crossover design. Subjects were studied on 2 separate days in the same week. Two 6MWTs-one indoors and the other outdoors-were performed on each study day, with a rest in between. The test order was randomly selected on the first day and reversed on the second day. Outdoor tests were performed on days of moderate weather conditions (mean temperature +/- standard deviation, 21 degrees +/-3 degrees C; mean wind speed, 15+/-7km/h; no precipitation) and on a flat surface (sidewalk). SETTING: Outpatient rehabilitation program in Ontario. PARTICIPANTS: Eighteen subjects with COPD (10 men, 8 women; age, 70+/-8y), 5 using supplemental oxygen at rest (forced expiratory volume in 1s, 1.0+/-0.3L; 42%+/-8% of predicted). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Distance walked in 6 minutes (in meters), duration of rest (in seconds), and change in rate of perceived dyspnea. RESULTS: There was no significant effect of setting (indoors vs outdoors) on distance walked (394+/-86m vs 398+/-84m, P=0.4), duration of rest (13+/-28s vs 9+/-20s, P=0.4), or change in rate of perceived dyspnea (2.3+/-1.7 vs 2.3+/-2.0, P=0.8). Testing day had no significant effect on walk test performance (all P>0.1). CONCLUSIONS: The results indicate that the 6MWT performed outdoors within reasonable climatic parameters may be reflective of 6MWT performance indoors.     

Step Activity Monitor: accuracy and test-retest reliability in persons with incomplete spinal cord injury

Recovery of walking after incomplete spinal cord injury (iSCI) is a common focus of rehabilitation, but few measurement tools capture walking performance outside the clinic or laboratory. This study determined the accuracy and test-retest reliability of the Step Activity Monitor (SAM), a microprocessor-driven accelerometer that measures walking activity. We evaluated 11 individuals with iSCI during replicate 6-minute walk tests (6MWTs) and 10-meter walk tests (10mWTs) scheduled <1 week apart. The SAM was 97% accurate compared with hand-tallied step counts. SAM values were stable across repeated walking performances (intraclass correlation coefficient = 0.97-0.99). Standard error of measurement values were 6.0 steps and 0.8 steps for the 6MWT and 10mWT, respectively. Ninety-five percent confidence intervals were 203.7 to 177.0 steps for the 6MWT and 16.1 to 12.7 steps for the 10mWT. The SAM is an accurate and reliable device for capturing walking activity in individuals with iSCI.     

The six‐minute walk test in outpatients with obesity: reproducibility and known group validity

Background and Purpose . To assess the reproducibility and validity of the six‐minute walk test (6MWT) in men and women with obesity in order to facilitate evaluation of treatment outcome. Method . A test—retest design was used to test reproducibility and a comparative design to test known group validity. Forty‐three obese outpatients (16 male), mean age 47 (21–62) years, mean body mass index (BMI) 40 (3–62)kg‐m^–2 performed the 6MWT twice within one week. Intraclass correlation (ICC1.1) and measurement error (S_w) were calculated from the mean square values derived from a one‐way repeated‐measures ANOVA (fixed effect model). The reproducibility was also analysed by means of coefficient of variation (CV) and the Bland Altman method including 95% limits of agreement. The variance of the distance walked was analysed by means of regressions. The known group validity of the 6MWT (distance walked and the work of walking) in obese participants was shown by comparisons with 41 lean participants (18 male), mean age 47 (24–65) years, mean BMI 22.7kg‐m^–2 (19–25). Results . The obese group walked 534 m (confidence interval [CI] 508–560 the first and 552 m (CI 523–580) the second walk (p < 0.001). S_w was 25 m, CV 4.7%, ICC1.1 was 0.96. The limits of agreement were –46 m+80 m. The validity tests showed that they walked 162 m shorter (p < 0.001) and performed much heavier work (p < 0.001) than the lean group. In the obese group, BMI alone explained 38% of the variance of the distance walked. Conclusions . The 6MWT showed good reproducibility and known group validity and can be recommended for evaluating walking ability in subjects with obesity. For individual evaluation, however, an improved walking distance of at least 80 m was required to make the difference clinically significant. Despite shorter walking distance the obese participants performed heavier work than the lean. Copyright © 2008 John Wiley & Sons, Ltd.     

Predictors of energy cost during stair ascent and descent in individuals with chronic stroke

[Purpose] This study aimed to determine which clinical measures of walking performance and lower limb muscle strength would predict energy cost during stair ascent and descent in community-dwelling individuals with stroke. [Subjects and Methods] Regression analysis of cross-sectional data from 55 individuals between one and five years post-stroke was used to investigate the measures of walking (speed and distance covered during the 6-minute walk test [6MWT]), and strength of the paretic knee extensor and ankle plantar flexor muscles would predict energy cost during stair ascent and descent. [Results] Three predictors (habitual walking speed, distance covered during the 6MWT, and strength of the paretic knee extensor muscles) were kept in the model. Habitual walking speed alone explained 47% of the variance in energy cost during stair ascent and descent. When the strength of the paretic knee extensor muscles was included in the model, the explained variance increased to 53%. By adding the distance covered during the 6MWT, the variance increased to 58%. [Conclusion] Habitual walking speed, distance covered during the 6MWT, and strength of the paretic knee extensor muscles were significant predictors of energy cost during stair ascent and descent in individuals with mild walking limitations.Key words: Stroke, Energy metabolism, Stairs     

Six‐minute walk test in obese children and adolescents: Reproducibility and validity

Background and Purpose . The six‐minute walk test (6MWT) is increasingly used in clinical practice. The aims of this study were to determine the reproducibility of the 6MWT in obese children and adolescents, to describe walking capacity in this population and compare the results with values from normal‐weight children (known group validity), and, finally, to describe the correlation between distance walked and estimated maximum oxygen uptake (VO₂max). Methods . Reproducibility was determined by a test–retest design and known group validity by a comparative design. The 6MWT was first test–retested in 49 obese children (30 boys, 19 girls, 8–16 years, body mass index [BMI] 24.9–52.1 kg?m^?2). Then, for validation, 250 obese children (126 boys, 124 girls, 8–16 years, BMI 23.2–57 kg/m²) and 97 normal‐weight children (48 boys, 49 girls, 8–16 years, BMI 13.3–23.2 kg·m^?2) performed the 6MWT. The obese children also performed a sub‐maximal bicycle ergometry test. Results . In the test–retest, the obese children walked 571 m the first test and 57 m the second (p = 0.578). The measurement error (S_w) was 24 m, coefficient of variation (CV): 4.3% and the intraclass correlation (ICC1:1): 0.84. Repeatability was 68 m, and limits of agreement were +71 and ?65 m. In comparison mean (standard deviation), six‐minute walk distance (6MWD) in the obese children was 571 m (65.5), and in the normal‐weight children, 663 m (61.1) (p < 0.001). The correlation between 6MWD and estimated VO₂max (r = 0.34) was low. Conclusions . The 6MWT showed good reproducibility and known group validity, and can be recommended for use in clinical practice in the studied population. To evaluate individual outcomes after intervention, the 6MWD needs to change by >68 m to be statistically significant. The 6MWD performed by obese children averaged 86% of the distance normal‐weight children walked. In obese children, the correlation between 6MWD and estimated VO₂max was low, hence the 6MWT cannot substitute a bicycle ergometry test. Copyright © 2008 John Wiley & Sons, Ltd.     

Mobility beyond the clinic: the effect of environment on gait and its measurement in community-ambulant stroke survivors

OBJECTIVE: To explore the impact of a complex community environment on gait parameters (speed, step length and cadence) for community-dwelling participants with a previous stroke, and compare outcome measures commonly used in a clinical environment. DESIGN: Repeated measurement of participants in different environments. SETTING: One clinic and two community environments (suburban street and shopping mall). SUBJECTS: Thirty community-dwelling stroke participants with chronic stroke who were classified according to gait speed (20-50 m/min on 10-metre timed walk) as marginal community walkers. OUTCOME MEASURES: During a six-minute walk test (6MWT) a step activity monitor (SAM) and odometer were used to calculate gait speed, step length and cadence. The 10-metre timed walk (10MTW) was measured in a clinic environment. ANALYSIS: A mixed linear model examined differences in gait measurements in the different environments. Bland-Altman analysis illustrated agreement between gait speed measures (6MWT and 10MTW). RESULTS: A statistically significant, but not a clinically significant difference in gait speed between some environments was found. Gait speed was slowest in the mall and fastest in the street with a difference of only 2.1 m/min between these environments (95% confidence interval (CI) -3.8 to -0.5, P<0.01). Comparison of clinic 10MTW and street 6MWT showed wide limits of agreement (-18.5 to 16.9 m/min) which improved for clinic 6MWT and street 6MWT comparisons (-5.7 to 8.9 m/min). CONCLUSION: Despite residual gait deficit, the gait parameters of these chronic stroke survivors did not deteriorate markedly under challenging conditions. The 6MWT is recommended as a clinical measure for community ambulation.     

Six-minute walk test in adults with cerebral palsy. A study of reliability

OBJECTIVE: To determine the reliability of a six-minute walk test in adults with cerebral palsy. DESIGN: Four repeated walk tests during two weeks. SETTING: The tests were conducted in a 40-m-long corridor at a rehabilitation centre for outpatients. SUBJECTS: Twenty-five adults (9 women and 16 men) with CP. Mean age 36 (26-58) years. Twelve subjects walked with walking aids and 13 without. Interventions: No intervention. MEASURES: The subjects were instructed to walk as far as possible for 6 min. The distance walked, heart rate and perceived exertion were assessed. RESULTS: Mean distances walked by the subjects in the four tests were 316, 336, 341 and 345 m. The repeatability between test 1 and the other tests was 66 m, and when the first walk test was excluded 40 m. The coefficient of variation (CV) between test 1 and the other tests varied between 7.1 and 8.7%, and when the first walk test was excluded between 3.7 and 4.5%. Intraclass correlation (ICC 1.1) was 0.97 in the four tests, and when the first walk test was excluded 0.99. Walking distance was longer (P<0.01) and varied less in subjects walking without walking aids (n = 13) compared with subjects using walking aids (n = 12). CONCLUSIONS: Six-minute walk test showed high reliability, with a repeatability of 40 m. One practice test is recommended, as the walking distance in the first test was significantly shorter (P<0.01) than the other three tests.     

The 6-minute walk distance cannot be accurately assessed at home in people with COPD

Abstract

Purpose: The 6-minute walk test (6MWT) is commonly used to measure exercise capacity in COPD, but it is unclear if this test is accurate when performed at home. This study aimed to determine whether exercise capacity can be accurately assessed at home using the 6MWT in COPD. Methods: A total of 19 participants with stable COPD (mean [SD] FEV₁/FVC 52[13]) undertook the 6MWT at home and at the hospital, in random order, with two tests performed on each occasion. Hospital tests were conducted on a 30-metre walking track whilst home tests (indoor or outdoor) were conducted using the longest available track. Agreement for 6-minute walk distance (6MWD) was examined using the Bland and Altman method. Results: The track length at home was mean [SD] of 17[9]?m. The home 6MWD was shorter than the hospital 6MWD (mean 30?m shorter, limits of agreement ?167 to 102?m). For the home tests, a shorter track length was associated with a greater reduction in 6MWD (r_s?=?0.59, p?=?0.01), but not an increased number of turns (r_s?=??0.41, p?=?0.08). Conclusions: The 6MWD underestimates exercise capacity when conducted at home in COPD. Alternative tests suitable for the home environment should be considered if a comprehensive assessment is to be performed at home.

• Implications for Rehabilitation

• The 6-minute walk test is commonly used to assess change in exercise capacity following pulmonary rehabilitation in patients with chronic obstructive pulmonary disease, and may be conducted on varying track lengths, indoors or outdoors.

• When conducted at home, the 6-minute walk test underestimates exercise capacity in chronic obstructive pulmonary disease, due to a shorter track length available in the home environment.

• This suggests that results from 6-minute walk tests performed at home environment cannot be directly compared to results from centre-based tests

     

Evaluation of a new device to prevent falls in persons with Parkinson's disease

Purpose. To compare walking characteristics of individuals with Parkinson's disease (PD) using a new walking aid, the WalkAbout, with usual walking.

Method. Fifteen subjects with PD were recruited. Subjects walked in their usual fashion and then walked again in the WalkAbout. Gait parameters, 5-min walk, and oxygen consumption were recorded.

Results. Stride lengths were shorter when using the WalkAbout. On an average, the distance walked in 5 min and the oxygen uptake was not different when walking with the WalkAbout compared with the usual walk. Eight subjects (responders) walked further with the WalkAbout compared to their usual walk (164.90 ± 55.72 m vs. 140.82 ± 55.94 m). Seven subjects (non-responders) walked a shorter distance while using the WalkAbout compared to their usual walk (241.79 ± 73.06 m vs. 281.24 ± 82.83 m). Compared to non-responders, responders were older, had more severe disability, and were more likely to use an assistive device for walking. Responders walked more slowly, had a shorter stride length, and walked shorter distances in 5 min than non-responders.

Conclusion. The WalkAbout may help persons with PD who have more severe disability to walk farther. These data could be beneficial in selecting a helpful walking aid for persons with PD.     

The use of the 6-min walk test as a proxy for the assessment of energy expenditure during gait in individuals with lower-limb amputation

The objective of this study was to determine, and compare, the utility of the 6-min walk test (6 MWT) and self-selected walking speed over 15 m as proxies for the assessment of energy expenditure during gait in individuals with lower-limb amputation. Patients with unilateral, transfemoral amputation (n=6) and patients with unilateral, transtibial amputation (n=10) from community-based support groups participated in this study. Age-matched and body mass index-matched able-bodied controls (n=28) from a sample of convenience also participated. The main outcome measures were as follows: (a) distance, heart rate, oxygen consumption and oxygen cost during the 6 MWT and (b) self-selected walking speed over 15 m. Oxygen cost did not correlate significantly with self-selected walking speed over 15 m (ρ=-0.329) or average walking speed during the 6 MWT (ρ=-0.350). Significant correlations were not present between oxygen cost and the walking speed during the 6 MWT (range, ∣ρ∣: 0.210-0.531), although walking speeds at particular times of the 6 MWT demonstrated stronger correlations than others. Walking speed in the third min of walking during the 6 MWT recorded the strongest correlation with peak oxygen cost (ρ=-0.531). The 6 MWT is a submaximal measure in persons with lower-limb amputation. Self-selected walking speed over 15 m was not an appropriate proxy for the assessment of the energy cost of gait. Individuals with a lower-limb amputation require approximately 3 min of continuous walking to re-establish homoeostasis in heart rate, oxygen consumption and oxygen cost. The nonsignificant correlation between walking speeds during the 6 MWT and oxygen cost suggest that the 6 MWT can provide an indication of oxygen cost, but caution should be exercised when using it as a sole proxy for the measurement of oxygen cost in individuals with lower-limb amputation.     

Nordic walking for geriatric rehabilitation: a randomized pilot trial

Purpose: There is a need to identify effective interventions to promote walking capacity in seniors. This study compares nordic walking (NW) and usual overground walking (OW) and estimates the relative efficacy in improving walking capacity (endurance and gait speed) of the elderly. Method: Single blind, site-stratified, randomized, pilot trial designed to estimate the amount of change with NW and OW. Main outcomes were distance walked measured by 6-min walk test (6MWT) and comfortable gait speed measured by 5-meter walk test (5MWT). Explanatory variables were age, sex, number of comorbidities, walking aids, balance, pain, and leg function. Results: NW and OW participants improved, respectively, 45 and 41 m on 6MWT and increased their gait speed by 0.14 and 0.07 m/s, respectively. NW effect sizes were moderate for 6MWT (ES = 0.53) and large for gait speed (effect size (ES) = 0.68). OW demonstrated moderate effect size for 6MWT (ES = 0.53) but a small one for gait speed (ES = 0.33). Relative efficacy, which was obtained from the ratio of NW and OW effects’ sizes, was 1 for 6MWT and 2.06 for gait speed. Conclusions: NW is 106% more effective in improving gait speed among elderly than OW.

Implications for Rehabilitation

• Elderly are the fastest growing segment of the population. With advanced age, greater number of disabilities, and consequently mobility limitations, are observed among this group.

• Nordic walking is a more intensive form of walking, using muscles of upper and lower body. There’s evidence that nordic walking leads to greater cardiorespiratory workload without an increase in the level of exertion.

• In this study, nordic walking was 106% more efficient than regular walking in improving gait speed among the elderly.

• Clinicians specialized in geriatric rehabilitation may contribute to improve gait speed of seniors by adding nordic walking, a non-expensive and feasible option, to their physiotherapy sessions.

     

Responsiveness and predictability of gait speed and other disability measures in acute stroke

OBJECTIVES: To identify the most responsive method of measuring gait speed, to estimate the responsiveness of other outcome measures, and to determine whether gait speed predicts discharge destination in acute stroke. DESIGN: A prospective cohort study. SETTING: Five acute-care hospitals. PATIENTS: Fifty subjects with residual gait deficits after a first-time stroke. INTERVENTIONS: Five- (5mWT) and 10-meter walk tests (10mWT) at comfortable and maximum speeds, with 2 evaluations conducted an average +/- standard deviation (SD) of 8 +/- 3 and 38 +/- 5 days poststroke. MAIN OUTCOME MEASURE: Standardized response mean (SRM = mean change/SD of change) was used to estimate responsiveness for each walk test, the Berg Balance Scale, the Barthel Index, the Stroke Rehabilitation Assessment of Movement (STREAM), and the Timed Up and Go (TUG). RESULTS: The SRMs were 1.22 and 1.00 for the 5mWT, and.92 and.83 for the 10mWT performed at a comfortable and maximum pace, respectively. The SRMs for the Berg Balance Scale, the Barthel Index, the STREAM, and the TUG were 1.04,.99,.89, and.73, respectively. The probability of discharge to a rehabilitation center for persons walking at < or = 0.3m/s or > 0.6m/s at the first evaluation was.95 and.22, respectively. CONCLUSIONS: The 5mWT at a comfortable pace is recommended as the measure of choice for clinicians and researchers who need to detect longitudinal change in walking disability in the first 5 weeks poststroke.     

Clinometric properties of the six-minute walk test in individuals undergoing rehabilitation poststroke

The 6-minute walk test (6MWT) is commonly used to measure walking ability. The purpose of this study was to determine the test-retest reliability and concurrent and construct validity of the 6MWT in patients who were actively undergoing inpatient rehabilitation poststroke. Thirty-seven patients undergoing inpatient rehabilitation after a stroke participated; mean age was 66.3 years and mean time since stroke was 33.7 days. Patients underwent two 6MWT trials with 1–3 days between trials. Additional outcome measures taken were gait speed and the Functional Independence Measure^TM (FIM^TM). The 6MWT exhibited high test-retest reliability; ICC_2,1 0.973 (95% CI=0.925–0.988) and a minimal detectable change (MDC₉₀) of 54.1?m. The 6MWT was strongly to moderately correlated with gait speed (r=0.89), locomotion (walk) FIM^TM (r=0.69), and motor FIM^TM (r=0.52). The 6MWT is a clinically useful measure of walking ability poststroke. It is reliable and is related to other measures of walking ability and function that are commonly used during rehabilitation after stroke.     

Characteristics of people with chronic lung disease who rest during the six-minute walk test

Wong R, Sibley KM, Hudani M, Roeland S, Visconti M, Balsano J, Hill K, Brooks D. Characteristics of people with chronic lung disease who rest during the six-minute walk test.

Objectives

To examine the incidence of resting during the 6-minute-walk test (6MWT) in patients with chronic lung disease (CLD) and to explore differences in functional exercise capacity and response to pulmonary rehabilitation (PR) between resters and nonresters.

Design

Retrospective chart review.

Setting

Inpatient PR program.

Participants

Individuals (N=211) who performed the 6MWT at admission and discharge from PR.

Interventions

Not applicable.

Main Outcome Measures

Primary outcomes were total distance walked (6-minute walk distance [6MWD]) and rest frequency and duration. Secondary outcomes were walking speed, end-test dyspnea, and the Chronic Respiratory Questionnaire (CRQ).

Results

At admission, 45 people (21%) rested 1 to 4 times during the 6MWT (total duration, 105±80s) and 166 people walked continuously. At discharge, 9 people continued to rest (total duration, 28±55s). At admission, nonresters walked 315±93m, whereas resters walked 197±83m (P<.0001), and 6MWD increased in both groups after PR (P<.0001). Nonresters increased their walking speed at discharge, but resters did not (interaction P<.001). At admission, the mastery domain of the CRQ was 0.8 point lower in resters (3.7±1.2) compared with nonresters (4.5±1.7; P=.01). Resters' end-test dyspnea scores decreased from 5.7±0.3 to 4.3±0.2 from admission to discharge, whereas nonresters' end-test dyspnea scores did not significantly change from 4.5±0.2 to 4.2±0.2 at discharge (interaction P<.05).

Conclusions

One in 5 individuals with CLD rest during the 6MWT. Decreasing rest duration or increasing walking speed reflects different strategies used to improve 6MWD after rehabilitation, both suggesting a positive effect of PR. This may be related to improvements in an individual's sense of control over dyspnea. Future work should investigate potential factors related to resting during the 6MWT.     

Periodic sound-based 6-minute walk test forpatients with Duchenne muscular dystrophy:a preliminary study

[Purpose] The purpose of this study was to verify if a periodic sound-based 6-minute walk test with the best periodic sound could be used to evaluate physical endurance more precisely than the conventional 6-minute walk test. [Subjects] The subjects were healthy subjects and 6 ambulant patients with Duchenne muscular dystrophy. [Methods] The subjects initially walked for 1 minute to a long-interval metronome sound, and the walking distance was measured. The sound interval was then gradually shortened, and the subjects walked for 1 minute for each of the intervals. The best periodic sound was considered to be the periodic sound used when the subject walked the longest distance in 1 minute, and the process of determining it was referred to as the period shortening walk test. This study administered the 6-minute walk test with the best periodic sound to twenty healthy subjects and 6 ambulant patients with Duchenne muscular dystrophy and compared the walking distance. [Results] The periodic sound-based 6-minute walk test distances in both the healthy subjects and the patients were significantly longer than the conventional 6-minute walk test distances. [Conclusion] The periodic sound-based 6-minute walk test provided a better indication of ambulatory potential in an evaluation of physical endurance than the conventional 6-minute walk test.     

Exploring Associations with 6-Minute Walk Test Performance in Adolescents and Young Adults with Down Syndrome: a Pilot Study

Six-minute walk test (6MWT) has been shown to be a valid and reliable measure of functional performance with respect to mobility in individuals with Down syndrome (DS). However, a wide variability of walking distance was observed from previous studies. Thus, there is a need to investigate the possible influencing factors of walking distance of the 6MWT in this population. In the current study, fourteen adolescents and young adults with DS, aged 14-30 yr. were recruited. Anthropometric variables, such as chronological age (CA), mental age (MA), Body Mass Index (BMI), level of physical activity (PA), grip strength, represented as muscular strength, leg length, resting heart rate (RHR), exercise heart rate (EHR) and walked distance of 6MWT (6MWD) were measured during their laboratory visit. Our results indicated the positive associations between the level of PA, grip strength, leg length and 6MWD. The total of 37.7% of the variance in 6MWD can be explained while considering the level of PA and grip strength in this population. Future research is still needed to include elderly populations with DS and more measures (i.e., motivation, leg length) to implement effective intervention and optimize functional performance in individuals with DS.