Six Minute Walk Test (6MWT)

The 6MWT is an assessment to measure the distance a person is capable of walking on a flat, hard surface in 6 minutes. It is a useful test to measure the response of all the bodily systems that a person uses while exercising. These include the respiratory and cardiovascular systems, blood circulation, and muscle movement.

The goal is to walk as far as possible within the 6-minute time frame, and the person sets their own pace. As it is a measure of walking, which is a part of daily living, it is likely a better representation of a person’s functional exercise level than intense exercise.

Purpose

The 6MWT measures exercise tolerance in people with various health conditions. Not only is the test a way to measure the general health of an individual, but a doctor can also use it to monitor the effectiveness of the current treatment plan and see whether it is improving a person’s condition.

For example, doctors commonly use it to assess individuals with heart or lung conditions such as:

• Chronic obstructive pulmonary disease (COPD): COPD is an umbrella term for conditions involving airway obstruction, such as emphysema and chronic bronchitis.
• Pulmonary hypertension: This is high blood pressure in blood vessels going from the heart to the lungs.
• Interstitial lung disease: These are conditions that cause progressive scarring of lung tissue, such as idiopathic pulmonary fibrosis.
• Heart diseases: Heart disease refers to conditions that affect the heart, such as heart failure, in which the heart does not work as well as it should.

Additionally, doctors may include the test in a pre-lung transplant evaluation, which is a series of tests that show a person’s capacity to withstand the surgery.

Although the original purpose of the test was to assess people with heart and lung conditions, doctors can use it to measure exercise capacity in older adults and children with other conditions, such as stroke, rheumatic conditions, and neurological conditions.

How to perform the 6MWT

Someone undergoing the test can expect the following:

• Before the test starts, the tester measures the participant’s pulse, blood pressure, oxygen level, and breathlessness.
• The participant receives the instructions to walk back and forth at their own pace to a designated spot for 6 minutes.
• The participant may slow down or take a break as necessary while standing.
• The tester instructs the participant to say if they experience trouble breathing or chest pain.
• Both the tester and participant should keep note of the number of lengths that the participant completes, as the tester will use this to calculate their score.
• After the 6MWT, the tester will again measure the participant’s pulse, blood pressure, oxygen level, and breathlessness.

Before performing the 6MWT, it is advisable that people avoid the following:

• eating a heavy meal
• wearing restrictive clothing
• smoking
• drinking alcohol
• exercising vigorously

Scoring system and normal values

The scoring involves figuring out the distance that a person has covered by multiplying the number of lengths by the distance of the track. For example, if a person completes 40 lengths of a 12-meter (m) track, multiplying 40 by 12 gives a score of 480 m.

Evidence suggests that the score range for healthy adults is 400–700 m. However, factors such as age, sex, and underlying health conditions can alter this value.

What the scores mean

The higher a person’s score, the better their exercise tolerance. A low score correlates with lower function.

The results of the 6MWT can help doctors evaluate the effectiveness of therapeutic intervention to increase exercise tolerance. After reviewing an individual’s score, doctors may change their medications or exercise program.

However, when doctors look at the scores of tests that took place at different times — such as 6 months or a year apart — they will need to evaluate any change based on how it compares with the minimal detectable change (MDC). The MDC is the minimum difference in score to ensure that the change is not due to an error.

Doctors will also consider the minimal important difference (MID), which is the smallest change in a treatment outcome that an individual would identify as clinically important.

Although the MID varies slightly depending on the test method and study population, the available evidence suggests that it is about 30 m.

A 2019 article notes that doctors can use 6MWT scores to predict the severity of lung conditions or the likelihood that they will be fatal. A 2019 review suggests that the 6MWT can also provide reliable information on the everyday functional ability and outlook of individuals with heart failure.

Considerations for the 6MWT

Those helping the person carry out the test will need to take the following steps where applicable:

• Document any braces or assistive devices that a participant uses during the test.
• Record a participant’s score as zero if they are unable to walk.
• Stop the test if a person needs to sit and record the distance that they have covered up until that point as their score.

Risks and safety

The American Lung Association (ALA) notes that doctors consider the 6MWT to be a low risk medical assessment. The tester watches the person for signs of chest pain or breathing trouble. Oxygen and other emergency treatment supplies are on hand in case an individual needs them.

How to prepare

In addition to not eating a heavy meal or performing rigorous exercise prior to the test, the ALA adds that people should prepare by:

• wearing comfortable clothes and shoes
• taking any usual medications
• using any usual walking aids, such as a cane or walker, if necessary

Summary

The 6MWT involves walking for 6 minutes to measure a person’s exercise capacity. It is a useful and safe test that can help a doctor evaluate a person’s general health and the effectiveness of current treatments. A doctor may suggest the test for people with heart or lung conditions.

A doctor can compare the score with previous results to check for improvements . If a score declines, it may suggest that a condition is progressing, whereas a substantial increase in the score may indicate that a treatment is effective.