Spinal muscular atrophy (SMA) is an inherited neurodegenerative disease characterized by the death of motor neurons in the brain and spinal cord. Motor neurons are nerve cells that control voluntary muscle movement. SMA patients experience progressive muscle weakness and atrophy, which is associated with fatigue, and decreased mobility and endurance.

The six-minute walk test (6MWT) is an easily administered, reliable, and standard test that has been approved by the U.S. Food and Drug Administration and the European Medicines Agency to assess the status of motor function in patients with neuromuscular disorders including SMA.

How is the 6MWT performed?

The 6MWT can be performed in a small area such as a hallway. It does not require any advanced equipment or training for technicians. The walking course is generally 30 meters in length and marked by cones so that the test taker can easily identify the course.

Patients are asked to walk at their fastest pace to cover as much of the 30-meter distance as possible during a six-minute interval. Chairs may be provided along the course so that they can sit during the test if needed because of fatigue or mobility issues.

Several readouts may be recorded by the technician during the test such as:

  • The total distance walked in the six-minute interval.
  • The distance covered per minute.
  • The time taken to complete one course length (30 meters).

The 6MWT is simple enough to use with children as well as adults. However, certain patients are advised not to take this test, including those who have been diagnosed with unstable angina, who have had a heart attack in the previous month, or who have a resting heart rate exceeding 120 beats per minute, a systolic blood pressure of more than 180 mm Hg, and a diastolic blood pressure of more than 100 mm Hg.

Clinical applications of the 6MWT for SMA

The 6MWT is used for the clinical evaluation of fatigue, muscle strength, and walking ability in SMA patients. It is a simple test that can be used periodically to study disease progression or severity.

The test can also be used to evaluate the efficacy of different therapies, especially those intended to improve mobility, and to identify patients that need to be targeted for a particular treatment.

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