Six-Minute Walk Test (6MWT)

Overview

We conducted a literature search to identify all relevant publications on the psychometric properties of the 6MWT in individuals with stroke.

Floor/Ceiling Effects

The 6MWT is a continuous variable without ceiling effects (Kosak & Smith, 2005).

Reliability

Test-retest
Eng, Dawson, and Chu (2004) examined the test-retest reliability of the 6MWT in 12 community-dwelling individuals with chronic stroke. The test-rest reliability of the 6MWT was found to be excellent for distance covered in meters (ICC = 0.99) and for the submaximal exercise variable Vo2 (ml/kg.min) (ICC = 0.96).

Flansbjer, Holmback, Downham, Patten, and Lexell (2005) studied the reliability of gait performance tests in 50 men and women with hemiparesis after stroke (chronic stroke). They reported the 6MWT had excellent test-retest reliability (ICC = 0.99) with smallest real differences of 13% (SRD) when compared to the Timed Up & Go, gait speed tests, and stair climbing ascend and descend tests.

Fulk, Echternach, Nof, and O’Sullivan (2008) examined the test-retest reliability of the 6MWT in 37 clients undergoing inpatient rehabilitation post-stroke. Clients were on average 33.7 days post-stroke and a mean age of 66.3 years. Clients were administered the 6MWT twice, with 1-3 days between trials. The 6MWT was found to have excellent test-retest reliability (ICC = 0.97).

Liu, Drutz, Kumar, McVicar, Weinberger, Brooks et al. (2008) investigated whether a practice effect as verified by various criteria including test-retest reliability occurred across 2 trials of the 6-minute walking test on 91 people with stroke. Participants were administered the 6MWT twice with 30-minutes between trials. Test-retest reliability calculated using Intraclass Correlation Coefficients (ICC) was excellent (ICC = 0.98).

Intra-rater & Inter-rater
Kosak and Smith (2005) examined the inter- and intra-rater reliability of the 6MWT in 18 clients enrolled in an inpatient stroke rehabilitation program (28 ± 34 days post-stroke). The intra-rater reliability was found to be adequate (ICC = 0.74). The inter-rater reliability was also found to be excellent (ICC = 0.78).

Validity

Criterion

Concurrent
The 6MWT had an excellent correlation with Vo2 max in patients with stroke (r = 0.66) (Vo2 max is the maximum volume of the oxygen that the body can consume during intense whole body exercise, while breathing air at sea level) (Eng et al., 2004; Pang, Eng, & Dawson, 2005).

Tang, Sibley, Bayley, McIlroy, and Brooks (2006) administered the 6MWT to 36 individuals with stroke (sub-acute) and reported excellent correlations between the 6MWT and the Five Meter Walk Velocity for preferred (r = 0.79), and fast speed (r = 0.82). This suggests that the speed selected by the patient during the 6MWT was strongly related to velocities chosen during the Five Meter Walk Distance (Kelly, Kilbreath, Davis, Zeman, & Raymond, 2003; Tang et al., 2006).

Tang et al. (2006) found an adequate correlation between the 6MWT and both a record of patients’ average oxygen uptake during cardiopulmonary exercise test (Vo2peak) (r = 0.56) and exercise test duration (r = 0.60) in 36 clients with stroke. This suggests that even though the 6MWT may challenge the cardiorespiratory system, it appears to be more strongly influenced by walking speed rather than cardiorespiratory capacity (Tang, Sibley, Bayley, McIlroy, & Brooks, 2006).

Fulk et al. (2008) examined the concurrent validity of the 6MWT using Pearson product moment correlations and Spearman Rank correlation coefficients in 37 clients undergoing inpatient rehabilitation post-stroke. Clients were on average 33.7 days post-stroke and a mean age of 66.3 years. The 6MWT was compared to subscales of the Functional Independence Measure (FIM) (Keith, Granger, Hamilton & Sherwin, 1987). The 6MWT had an excellent correlation with discharge locomotion (walk) FIM scores (Spearman r = 0.69), and with discharge locomotion (walk) + stairs FIM scores (Spearman r = 0.69). The 6MWT had adequate correlations with discharge motor FIM scores (Pearson r = 0.52), and discharge total FIM scores (Pearson r = 0.45).

Predictive
Fulk, Reynolds, Mondal & Deutsch (2010) examined the predictive validity of the 6MWT and other widely used clinical measures (FMA LE, self-selected gait-speed, SIS and BBS) in 19 patients with stroke. The 6MWT was found to be an excellent predictor of mean steps per day (r = 0.68; P = 0.001). Although gait speed and balance were related to walking activity, only the 6MWT was found to be a predictor of community ambulation in patients with stroke.

Construct

Convergent
Kosak and Smith (2005) compared the 2MWT to the 6MWT in 18 clients with stroke. An excellent correlation was found between these two measures (r = 0.997).

Kosak and Smith (2005) compared the 12MWT to the 6MWT in 18 clients with stroke. An excellent correlation was found between these two measures (r = 0.99).

Patterson et al. (2007) administered both the Berg Balance Scale (BBS) (Patterson, Forrester, Rodgers, Ryan, Ivey, Sorkin, et al., 2007) and the 6MWT to 74 clients (43 men, 31 women) with chronic hemiparetic stroke. An excellent relationship was reported between the BBS and the 6MWT (r = 0.69).

Patterson et al. (2007) compared quadriceps eccentric paretic strength to the 6MWT in 74 individuals (43 men, 31 women) with chronic hemiparetic stroke. An adequate relationship was reported between the 6MWTand quadriceps strength (r = 0.57).

Pang, Eng, and Miller (2007) administered the Reintegration to Normal Living Index (RNL) and the 6MWT to 63 clients with chronic stroke. An adequate correlation was reported between these two measures (r = 0.35).

Fulk et al. (2008) examined the convergent validity of the 6MWT by comparing it to the 5MWT in 37 clients undergoing inpatient rehabilitation post-stroke. Clients were on average 33.7 days post-stroke and a mean age of 66.3 years. Using Pearson product moment correlation, the 5MWT and the 6MWT were found to have an excellent correlation (r = 0.89).

Known groups and Discriminant:
Not available.

Responsiveness

The table below summarizes studies that have examined the responsiveness of the 6MWT among individuals with stroke.

Authors Name Type of study Result of Study
(Kosak & Smith, 2005) Cross-sectional N=18 clients with stroke An inpatient stroke rehabilitation program (standard protocol as set out by the American Association of Cardiovascular and Pulmonary Rehabilitation) lasting 3.9 + 2 weeks of observation indicated that the responsiveness to change for the 6MWT as measured by standardized response mean (SRM) score was 1.52. This translates into a 2.4 fold increase in the distance walked by clients enrolled in this rehabilitation program.
(Duncan et al., 1998) RCT, pilot study N=20 clients with stroke The results of an 8-week home-based exercise program indicated a change of 59.4 meters on the 6MWT (mean changes = 195 ft) compared with 34.7 meters (mean changes = 114 ft) following usual care.
(Dean, Richards, & Malouin, 2000) RCT, pilot study N=12 clients with stroke A 4-week exercise class was offered to improve locomotor tasks (Dean et al., 2000). Participants achieved a change of 42.1 meters (SD = 119.0) in the 6MWT compared with only a 4.7 meter change following equal intensity of in upper-extremity (UE) intervention.
(Visintin, Barbeau, Korner-Bitensky, & Mayo, 1998) RCT, N=100 clients with stroke After 6 weeks of treadmill training with body weight support, the mean change in the distance walked in 6 minutes following the intervention was 102.8 meters (SD = 67.4) compared with 58.8 meters (SD = 72.2) in the control group.
(Salbach et al., 2004) RCT, N=91 stroke patients The efficacy of a task-oriented intervention in comparison to usual care in enhancing competence in walking with stroke was evaluated. Clients with a mild, moderate or severe walking deficit at baseline improved an average of 36 (SD = 96), 55 (SD = 56) and 18 m (SD = 23), respectively, in 6MWT performance at post-intervention.
(Duncan et al., 2003) RCT, N=100  stroke patients (Subacute phase) The efficacy of therapeutic exercise for individuals with subacute stroke was compared to usual care. The intervention group improved in 6MWT performance by an average of 28.2 meters (12.52%) more than the usual care group.
(Tanne, Tsabari, Chechik, Toledano, Orion, Schwammenthal, et al., 2008) RCT, N=52 post-minor ischemic stroke Three-month outpatient exercise program. Improvement in exercise capacity in the intervention group in comparison to the control group was demonstrated using the 6MWT (from 444 ± 90 at baseline to 557 ± 99 meters post-intervention in the exercise group; from 438 ± 101 at baseline to 418 ± 126 in the control group).
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