Borg Scale 6-Minute Walk Test: Purpose, Procedure, and Interpretation

What is the Borg scale 6-minute walk test?

The Borg scale 6-minute walk test (6MWT) is a submaximal exercise test used to assess functional exercise capacity and perceived exertion, primarily in clinical populations, by measuring the distance an individual can walk on a flat, hard surface in six minutes while simultaneously monitoring their subjective feeling of effort using the Borg Rating of Perceived Exertion (RPE) scale.

Understanding the 6-Minute Walk Test (6MWT)

The 6-Minute Walk Test (6MWT) is a widely recognized and simple measure of functional exercise capacity. Unlike maximal stress tests that push an individual to their physiological limit, the 6MWT is a submaximal test, meaning it assesses how far a person can walk at their own pace over a set period. It's particularly valuable for evaluating the overall functional status and prognosis of individuals with various chronic diseases.

• Purpose: The primary goal of the 6MWT is to measure the distance an individual can walk in six minutes. This distance serves as an objective measure of functional capacity, reflecting the integrated response of various bodily systems, including the pulmonary, cardiovascular, neuromuscular, and metabolic systems, during submaximal exercise.
• Procedure: The test is typically conducted in a long corridor (e.g., 30 meters or 100 feet) with clearly marked start and turn-around points. The participant is instructed to walk as far as they can, turning around quickly at each end, for a full six minutes. Standardized encouragement is usually provided by the administrator at regular intervals.
• Equipment: Minimal equipment is required: a stopwatch, a measuring tape to mark the walking course, a counter to track laps, and a chair for resting if needed. In a clinical setting, a pulse oximeter may be used to monitor heart rate and oxygen saturation.
• Standardization: To ensure reliable and comparable results, the 6MWT adheres to specific guidelines established by organizations such as the American Thoracic Society (ATS) and the European Respiratory Society (ERS). These guidelines cover course length, standardized encouragement, and reporting procedures.

Integrating the Borg RPE Scale

The Borg Rating of Perceived Exertion (RPE) scale is a crucial component when assessing the 6MWT, as it provides a subjective measure of the participant's perceived effort during the test.

• What is the Borg RPE Scale? Developed by Professor Gunnar Borg, the RPE scale is a numerical scale used to quantify an individual's perception of physical exertion. There are two common versions:
  • Borg RPE 6-20 Scale: This is the original scale, ranging from 6 (no exertion at all) to 20 (maximal exertion). It's designed to correlate with heart rate (e.g., RPE of 13 often corresponds to a heart rate of 130 bpm).
  • Borg CR10 Scale (Category Ratio Scale): This scale ranges from 0 (nothing at all) to 10 (maximal), with descriptors for various levels of intensity.
  • In the context of the 6MWT, the Borg RPE 6-20 scale is most commonly used to capture the participant's overall feeling of effort.
• Application in the 6MWT: Participants are typically asked to rate their perceived exertion using the Borg RPE scale at the beginning of the test (baseline), immediately after completing the six minutes, and sometimes at specific intervals during the test. They are asked to consider their overall feeling of exertion, including breathlessness, muscle fatigue, and general tiredness.

Who Benefits from the 6MWT with Borg RPE?

The 6MWT, especially when coupled with Borg RPE, is a versatile assessment tool used across various populations and settings.

• Clinical Populations:
  • Cardiopulmonary Disease: Widely used in patients with chronic obstructive pulmonary disease (COPD), heart failure, pulmonary hypertension, and cystic fibrosis to assess disease severity, monitor treatment effectiveness, and predict morbidity and mortality.
  • Pre- and Post-Surgical Assessment: Used to evaluate functional capacity before surgery (e.g., lung transplantation, cardiac surgery) and to track recovery afterward.
  • Rehabilitation Programs: Helps in setting exercise goals and monitoring progress in cardiac and pulmonary rehabilitation.
  • Neurological Conditions: Can be used in conditions like stroke, Parkinson's disease, or multiple sclerosis to assess walking endurance and functional mobility.
  • Geriatric Populations: Provides a safe and effective way to assess functional status and fall risk in older adults.
• Fitness Assessment: While primarily clinical, the 6MWT can also be adapted for general fitness assessment, particularly for individuals new to exercise, those with lower fitness levels, or older adults, to establish a baseline of aerobic capacity and track improvements in endurance.

Interpreting the Results

Interpreting the results of the Borg scale 6MWT involves considering both the objective distance walked and the subjective perceived exertion.

• Distance Covered:
  • Baseline Measurement: The initial distance walked provides a baseline of functional capacity.
  • Tracking Progress: Subsequent tests can show improvements (increased distance) or declines (decreased distance) in functional capacity, indicating the effectiveness of interventions or disease progression.
  • Normative Data: Reference equations, often adjusted for age, sex, height, and weight, exist to compare an individual's performance against expected values for healthy populations.
  • Minimal Clinically Important Difference (MCID): For many conditions, a change of approximately 30-50 meters in walking distance is considered a clinically meaningful improvement.
• Borg RPE Scores:
  • Perceived Effort at End: A higher RPE score at the end of the test indicates greater perceived effort for the distance covered, which might suggest poorer conditioning or increased symptom burden.
  • Correlation with Symptoms: Changes in RPE can correlate with changes in symptoms like dyspnea (shortness of breath) or leg fatigue, providing insight into the individual's experience of exercise.
  • Safety Monitoring: Extremely high RPE scores at low distances could signal a need for closer medical evaluation or adjustment of activity levels.
• Limitations: While valuable, the 6MWT has limitations. It's not a diagnostic test and doesn't provide specific information about the cause of exercise limitation. Its submaximal nature means it may not fully capture peak physiological capacity. External factors like motivation, prior activity, and the administrator's encouragement can also influence results.

Advantages and Disadvantages

Like any assessment tool, the Borg scale 6MWT offers distinct advantages and some disadvantages.

• Advantages:
  • Simplicity and Low Cost: Requires minimal equipment and training to administer.
  • Safety: A submaximal test, making it generally safe for a wide range of individuals, including those with significant health issues.
  • Ecological Validity: Simulates a common daily activity (walking), making its results highly relevant to real-world functional capacity.
  • Good Reproducibility: With standardized protocols, results are generally consistent when repeated.
  • Strong Prognostic Value: The distance walked is often a powerful predictor of morbidity and mortality in various chronic diseases.
  • Subjective Insight: The Borg RPE scale adds a crucial subjective dimension, offering insight into the patient's experience of exertion and symptoms.
• Disadvantages:
  • Effort Dependent: The test relies on the participant's maximal effort, which can be influenced by motivation.
  • Ceiling Effect: Highly fit individuals may not be sufficiently challenged to demonstrate their full functional capacity.
  • Non-Diagnostic: Does not identify the specific cause of exercise intolerance.
  • Practice Effect: Participants may perform better on subsequent tests due to familiarity with the procedure.
  • Environmental Factors: Temperature, humidity, and the walking surface can subtly influence performance.

Conclusion

The Borg scale 6-minute walk test is an invaluable, practical, and evidence-based tool for assessing functional exercise capacity and perceived exertion. By combining an objective measure of walking distance with the subjective experience of effort, it provides a holistic view of an individual's physical capabilities and limitations, making it a cornerstone in clinical evaluation, rehabilitation, and fitness monitoring for diverse populations.