Introduction:
In the realm of clinical assessments, healthcare professionals employ various tools to gauge the functional capacity, gait quality and overall well-being of their patients. One such test that has gained significant recognition is the 6-minute walk test (6MWT). Developed in the 1980s, this simple yet valuable assessment has become a cornerstone for evaluating the exercise tolerance and functional capacity of individuals with a wide range of medical conditions. Prolonged walking tasks such as the 6MWT (or the 2-Minute Walk Test) are typically viewed as a good indicator for demonstrating the ability to perform activities of daily living.
What is the 6-Minute Walk Test?
The 6MWT is a standardized, submaximal exercise test that measures the distance an individual can walk on a flat surface in six minutes. It is viewed as a test of aerobic capacity and gait function and is widely used among various clinical populations, including cardiology, pulmonology, geriatrics, Multiple Sclerosis, Parkinson’s Disease, stroke recovery, spinal cord injury, pain management, and rehabilitation. During the test, the participant is instructed to walk as far as possible in a measured corridor or track, and they are allowed to rest or slow down if needed. The primary outcome of the test is the total distance covered in six minutes, but other data such as heart rate, oxygen saturation, and temporal spatial gait metrics may also be recorded.
Analyzing Gait Measurements During the 6-Minute Walk Test
Historically, the 6MWT has been administered with nothing more than a stopwatch and a way to measure the distance traveled. While distance traveled during the test has been found to be a useful outcome measure (for example, it has been linked to mortality rates in patients with heart disease), researchers are working to monitor patients throughout the test to gain new insights. Oxygen consumption, heart rate and temporal spatial gait measures can be viewed throughout the 6 Minute Walk Test to look at changes in performance over time.
In one study, Hadouiri et al (2022) had 45 people with Multiple Sclerosis (PwMS) and 24 healthy controls perform the 6MWT with an instrumented walkway placed on one portion of the walking track used to complete the protocol. Spatial Temporal Gait measurements were calculated for the first 2 minutes, middle 2 minutes and final 2 minutes of the test. PwMS showed significant changes when comparing first 2-minute segment and the last 2-minute segment, while healthy individuals showed a minimal change. The PwMS were unable to maintain their gait pattern throughout the full six minutes and were unable to rebound once their gait started to decline. The normal population showed a slight change in gait pattern during the middle portion of the trial, but were able to rebound in their final 2 minutes back to initial performance. This study shows that identifying changes in gait pattern throughout the 6MWT can provide insight into fatiguability and how fatigue effects gait that cannot be identified with the traditional 6MWT output.
Improvements in Technology
Over the years, heart rate monitors, oxygen consumption spirometers and gait analysis technology have made it easier for researchers and clinicians to study patient populations using prolonged gait protocols. In early 2023, ProtoKinetics introduced a new feature in PKMAS 6.0 that allows for rapid decomposition of gait data that is collected on a Zeno Walkway System during extended gait analysis protocols, such as the 6-MWT. The partition statistics feature allows researchers and clinicians to look at gait changes over time more efficiently than ever before. Decomposing temporal spatial gait data during prolonged gait analysis protocols could lead to new insights into changes in performance in order to better understand changes over time for a multitude of patient populations.
Discussion
Quantification of performance during prolonged gait analysis protocols allow researchers and clinicians to identify how gait changes over time. This is important in understanding how gait looks as a subject fatigues. For example, decreases in velocity and increases in gait variability over the course of the 6MWT could imply that as a subject fatigues, their risk of falls increases. The 6MWT is done in a controlled environment so the examiner can be sure that the changes in gait over time are not due to external factors, such as perturbations or dual tasking. Understanding how gait changes over time can provide new insights into overall gait function and lead to a better understanding of fatiguability in various populations.
Hadouiri N, Monnet E, Gouelle A, Sagawa Y Jr., Decavel P. Locomotor Strategy to Perform 6-Minute Walk Test in People with Multiple Sclerosis: A Prospective Observational Study. Sensors. 2023; 23(7):3407. https://doi.org/10.3390/s23073407