Assessing aerobic capacity and endurance is useful for monitoring progress or determining the general level of preparedness of elite athletes. It is also a holistic diagnostic indicator of the state of cardiopulmonary and musculoskeletal systems involved in physical exercise.
Advancements in medical technology and the subsequent development of dedicated diagnostic tools have made measuring the various parameters associated with physical exertion easy and convenient, but are usually used only in specialised settings. There is, however, a simple test to evaluate the cardiovascular system of patients during a seemingly banal effort, walking for a period of 6 minutes.
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The 6-minute Walk Test (6MWT) was formalized by the American Thoracic Society and presented in its standardized form in 2002. It was originally intended for assessing exercise tolerance in patients with cardiopulmonary issues . However, clinicians also use the 6MWT for a wide variety of non-cardiopulmonary diseases, including neuromuscular conditions such as Charcot-Marie-Tooth disease and myasthenia gravis [2, 3].
In general, the 6MWT evaluates the responses of all the systems involved during physical exercises, such as cardiovascular and pulmonary systems, systemic and peripheral circulation, blood, neuromuscular system and muscle metabolism, but it does not supply exact information for specific Compared to stress ECG which offers diagnostic information at maximal exercise capacity, the 6MWT assesses functional capacity at submaximal level, at everyday physical activity levels . It is hence in many clinicians’ toolboxes as an evaluation method for functional exercise capacity in selected patients.
The indications for the 6MWT are numerous. They obviously include pathologies in which pulmonary function are altered such as lung transplantation, lung resection, severe asthma and cystic fibrosis [4-7]. It is also used for assessing exercise capacity and its evolution in patients with chronic obstructive pulmonary disease (COPD) or pulmonary arterial hypertension (PAH), or in cardiovascular rehabilitation programs [8-11].
The 6MWT is also useful in patients with cardiovascular diseases (CVDs) such as heart failure (HF) and peripheral artery disease (PAD) [12-15]. Those with the latter condition and poorly measured distance have higher rates of all-cause mortality, cardiovascular mortality, and mobility loss [16, 17]. More specifically, the 6MWT is an excellent indicator of the severity of the disease and of any performance improvement in response to therapeutic interventions .
Last but not least, are individuals with neurological and neuromuscular conditions like spinal muscular atrophy, fibromyalgia, Parkinson’s disease (PD) and multiple sclerosis (MS) [19-22]. The 6MWT also found use in assessing functional recovery in patients with total knee arthroplasty (TKA) . Even on its own, the 6MWT is a useful predictor of all-cause mortality risk .
The 6MWT is generally safe and well-tolerated by patients with the distinction of those with unstable angina and myocardial infarction (MI) in the month preceding the testing . Those are absolute contraindications. Relative contraindications are a resting heart rate of more than 120 bpm, a systolic blood pressure of more than 180 mmHg, and diastolic blood pressure of more than 100 mmHg . The testing should likewise be immediately stopped if the patient reports shortness of breath, chest pain or leg cramps or starts to stagger, exhibit diaphoresis or takes a pale appearance . Adhering to the testing protocol greatly mitigates the likelihood of such adverse reactions.
One of the reasons for the success of the 6MWT, apart from its well-researched and proven diagnostic value, is the availability of equipment needed to perform the testing and general convenience for both the examiner and patient. The only preparation the examinee should undertake is to wear appropriate walking shoes, comfortable clothing and avoid heavy meals or vigorous exercise before starting the test . This is in addition to continuing any existing medical regime (therapies, medications, etc.) and using any walking aids they usually use during their everyday activities .
The test itself should preferably be performed indoors or, weather permitting, outdoors on a flat, long surface with a length of at least 20 m . The length of the track should be marked every 3 m and the turn-around points should be marked with cones and the starting point with a bright-coloured tape . Other essential tools for the examiner are a stopwatch, lap counter, clipboard, sphygmomanometer, and an automated external defibrillator (AED) as a precaution .
The patient should rest for 10 minutes before the start of the test, have their blood pressure measured and asked to rate their baseline dyspnoea and overall fatigue using the Borg scale . The patient should then be instructed to start walking on the track (they can rest but they should be encouraged to continue) [i]. After 6 minutes have elapsed or the examinee has stopped and refused to continue (the reason for this should be duly noted), the examiner asks the patient to again rate their dyspnoea/overall fatigue and note/measure the walked distance. Now all that is left is the interpretation of results.
Watch the video on how to perform a 6-minute walk test using MESI mTABLET SPO2.
Comprehensive interpretation of 6MWT is solely dependent on the condition that led to a decrease in functional capacity. Any decrease in the walking distance during the 6MWT is indicative of a worsening of the underlying condition and any significant improvement, post-therapeutic intervention, is likely due to the intervention. What has considered a significant improvement is again dependent on the disease.
The 6-minute walking test (6MWT) is a versatile tool for assessing functional capacity in patients with a wide variety of pulmonary, cardiovascular, neurological, and neuromuscular conditions.