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The Six Minute Walk Test Explained
The 6MWT is a simple to administer and low-cost functional test that assesses the status of patients in a variety of cardiopulmonary conditions from heart failure to obstructive lung disease.
In the original study of 1998, Enright et al. set out to create gender-specific equations that can predict reference values for the six-minute walking distance in healthy adults. The study involved a cohort of 117 men and 173 women, aged 40 to 80 years. The median distance walked was 576 m for men and 494 m for women.
Oxygen saturation (SaO2), pulse rate, and the degree of dyspnea (Borg scale) were determined before and at the end of the walk.
The predictive equations are:
| Gender | Predicted 6-minute walk distance 6MWD) | 6MWD lower limit |
| Male | (7.57 x height in cm) – (5.02 x age) – (1.76 x weight in kg) – 309 | 6MWD – 153 |
| Female | (2.11 x height in cm) – (2.29 x weight in kg) – (5.78 x age) + 667 | 6MWD – 139 |
The predicted distance was found to be considerably correlated with age (r = -0.29), height (r = 0.393), weight (r = 0.08), and BMI (r = -0.17).
In practice, the 6MWT may be administered to all ages, from toddlers to elderly adults. The test is recognized for providing valuable information regarding the body’s systems during physical activity: from cardiovascular to pulmonary systems, metabolism, blood and peripheral circulation and activity of neuromuscular units.
The 6MWT has been shown to be a significant predictor of morbidity and mortality in pulmonary arterial hypertension (PAH), heart failure and peripheral arterial disease (PAD).
Do not administer the test if patient had unstable angina or myocardial infarction less than one month prior. Some other relative contraindications include a resting heart rate over 120, systolic blood pressure over 180 or diastolic blood pressure over 100.
The test must be stopped if the patient experiences chest pain, dyspnea, leg cramps or extreme muscle fatigue, evolving mental confusion or if staggering or pale appearance occur.
The table below summarizes some of the other conditions in which the test may have assessment value:
| Conditions 6MWT may be used to evaluate functional status in | ||
| Arthritis | Fibromyalgia | Multiple Sclerosis |
| Parkinson’s Disease | Spinal Cord Injury | Stroke |
| Muscle disorders | Spinal Muscular Atrophy | Charcot-Marie-Tooth Disease |
Please note that whilst a low 6MWT may provide some indication and can have prognostic properties, it remains non-diagnostic and should accompany other diagnostic tests relevant to the suspected conditions.
An increase in the distance walked between two subsequent tests may be interpreted as a basic improvement in mobility. The 6MWT result may be influenced by a variety of factors, some described in the table below:
| 6MWT Increasing Factors | 6MWT Decreasing Factors |
| Male gender | Female gender |
| Higher muscle mass | Higher body weight |
| Taller heights | Shorter heights* |
| Past performance of test | Patient’s decreased motivation / Older age |
| Patient’s increased motivation | Presence of cardiovascular or pulmonary condition |
*One criticism of the 6MWT refers to the fact that the predictive equations may be less accurate in shorter patients, who present naturally shorter strides.
The equipment required to perform the test is:
- One chair, positioned at one end of the walking course;
- Validated scale to measure dyspnea;
- Sphygmomanometer for blood pressure;
- Pulse oximeter;
- Stopwatch;
- The walking track should be marked;
- First aid kit, emergency plan and access to phone;
- Portable supplemental oxygen device.
The American Thoracic Society Guideline for the Six Minute Walk Test provides several guidelines on how to perform the standardized version of the test.
This test is a good alternative for patients who are too old or frail to perform other functional tests, such as the Duke Treadmill Test.
References
Original reference
Enright PL, Sherrill DL. Reference equations for the six-minute walk in healthy adults [published correction appears in Am J Respir Crit Care Med. 2020; 201(3):393]. Am J Respir Crit Care Med. 1998; 158(5 Pt 1):1384-1387.
Validation
Enright PL, McBurnie MA, Bittner V, et al. The 6-min walk test: a quick measure of functional status in elderly adults. Chest. 2003; 123(2):387-398.
Other references
ATS Committee on Proficiency Standards for Clinical Pulmonary Function Laboratories. ATS statement: guidelines for the six-minute walk test [published correction appears in Am J Respir Crit Care Med. 2016 May 15;193(10):1185]. Am J Respir Crit Care Med. 2002; 166(1):111-117.
Singh SJ, Puhan MA, Andrianopoulos V, et al. An official systematic review of the European Respiratory Society/American Thoracic Society: measurement properties of field walking tests in chronic respiratory disease. Eur Respir J. 2014; 44(6):1447-1478.
