Astrand-Rhyming Cycle Test: Protocol, Equipment, and VO2max Estimation

How to do the Astrand cycle test?

The Astrand-Rhyming cycle ergometer test is a widely recognized submaximal fitness assessment designed to estimate an individual's maximal oxygen uptake (VO2max) based on their heart rate response to a standardized workload, offering a practical and non-invasive measure of cardiorespiratory fitness.

What is the Astrand-Rhyming Cycle Ergometer Test?

Developed by Per-Olof Astrand and Irma Rhyming in the 1950s, the Astrand-Rhyming cycle ergometer test is a cornerstone in exercise physiology for assessing aerobic capacity. It operates on the principle that there is a linear relationship between heart rate, oxygen uptake, and work rate at submaximal intensities. By measuring a subject's heart rate at a specific, controlled workload on a stationary bicycle, the test provides an estimate of their VO2max, which is the maximum amount of oxygen an individual can utilize during intense, maximal exercise. This makes it a valuable tool for tracking fitness progress, prescribing exercise intensities, and identifying cardiovascular health risks without requiring maximal exertion.

Why Perform the Astrand Test?

Performing the Astrand-Rhyming test offers several distinct advantages for both individuals and fitness professionals:

• Safety and Accessibility: As a submaximal test, it carries a lower risk of adverse events compared to maximal exertion tests, making it suitable for a broader population. The equipment required (a cycle ergometer) is also commonly available in gyms and clinics.
• Cost-Effectiveness: It does not require expensive, complex laboratory equipment needed for direct VO2max measurement.
• Practicality: The test is relatively short (6 minutes of exertion) and easy to administer, making it efficient for group assessments or regular monitoring.
• Baseline and Progress Tracking: It provides a reliable baseline measure of cardiorespiratory fitness, allowing individuals and trainers to track improvements over time in response to training interventions.
• Exercise Prescription: The estimated VO2max can be used to tailor exercise programs, setting appropriate training zones and intensities.

Equipment Needed

To accurately perform the Astrand-Rhyming cycle test, you will need the following equipment:

• Cycle Ergometer: A mechanically braked ergometer (e.g., Monark, Bodyguard) that can accurately measure workload in Watts or kpm/min. It must have adjustable seat height and handlebar position.
• Heart Rate Monitor: A reliable chest strap heart rate monitor with a display to continuously track heart rate. Manual palpation can be used as a backup but is less accurate for continuous monitoring.
• Stopwatch: To precisely time the 6-minute test duration and heart rate measurements.
• Metronome: To help maintain the specified pedaling cadence (revolutions per minute, RPM).
• RPE Scale (Borg Scale): To monitor perceived exertion, though not strictly required for the calculation, it's crucial for safety.
• Data Sheet and Pen: To record heart rate, workload, and other relevant information.
• Astrand-Rhyming Nomogram or Calculation Formula: For estimating VO2max from the collected data.

Pre-Test Considerations and Safety

Before conducting the Astrand test, ensure the following:

• Medical Clearance: Individuals with known cardiovascular disease, metabolic disorders, or other health conditions should obtain medical clearance before performing any fitness test.
• Hydration and Nutrition: The subject should be well-hydrated and have avoided heavy meals for at least 2-3 hours prior.
• Rest: Ensure adequate rest the night before the test.
• Avoid Stimulants: Refrain from caffeine, nicotine, alcohol, and strenuous exercise for at least 24 hours before the test, as these can affect heart rate.
• Proper Bike Setup: Adjust the saddle height so there is a slight bend in the knee (25-30 degrees) at the bottom of the pedal stroke. Handlebars should be comfortable.
• Explain the Protocol: Clearly explain the test procedure, expected sensations, and the importance of maintaining the specified cadence to the subject.
• Emergency Plan: Have an emergency plan in place, including knowledge of first aid and access to medical assistance if needed.

Step-by-Step Protocol

Follow these steps carefully to administer the Astrand-Rhyming cycle test:

• Warm-up:

  • Instruct the subject to pedal at a light resistance (e.g., 50 Watts or 300 kpm/min) for 2-3 minutes at a cadence of 50 RPM. This allows the heart rate to stabilize and prepares the muscles.
  • Monitor the subject's comfort and ensure proper technique.

• Test Protocol (6 Minutes):

  1. Set Workload: After the warm-up, immediately set the test workload. The standard workloads are:
     • Untrained Females: 300 kpm/min (50 Watts)
     • Trained Females: 450 kpm/min (75 Watts)
     • Untrained Males: 600 kpm/min (100 Watts)
     • Trained Males: 900 kpm/min (150 Watts)
     • Note: Choose a workload that is expected to elicit a heart rate between 120-170 bpm for the subject. If the initial workload is too low or too high, adjustments may be made, but ideally, one workload is maintained for the entire 6 minutes.
  2. Maintain Cadence: The subject must maintain a constant pedaling cadence of 50 RPM throughout the 6-minute test. Use a metronome to assist with this.
  3. Monitor Heart Rate: Record the heart rate every minute. The critical heart rates for the calculation are those recorded during the 5th and 6th minutes.
  4. Steady State: The goal is for the subject's heart rate to reach a steady-state by the end of the test. A steady-state is defined as two consecutive minute heart rates (e.g., 5th and 6th minute) that differ by no more than 5 beats per minute (bpm). If steady-state is not achieved or the HR is outside the 120-170 bpm range, the test may need to be extended or repeated with an adjusted workload.
  5. Termination: The test is terminated after 6 minutes, provided a steady-state heart rate within the target range has been achieved.

• Cool-down:

  • After the 6 minutes of testing, instruct the subject to continue pedaling at a very light resistance for 2-3 minutes to gradually lower their heart rate and prevent blood pooling.
  • Monitor their recovery and well-being.

Data Collection and Calculations

Once the test is complete, you will use the collected data to estimate VO2max:

• Heart Rate (HR):

  • Calculate the average of the heart rates recorded during the 5th and 6th minutes. This average steady-state heart rate is used in the calculation.

• Workload (Watts or kpm/min):

  • Note the precise workload maintained during the test. (1 Watt = 6.12 kpm/min).

• Oxygen Uptake (VO2max) Estimation:

  • Using the Astrand-Rhyming Nomogram: This is the most common method. Locate the steady-state heart rate on the right-hand scale and the workload on the left-hand scale. Draw a straight line connecting these two points. The point where this line intersects the middle scale provides the estimated VO2max in L/min.
  • Using a Formula (Example for 50 RPM): While the nomogram is standard, formulas exist for specific ergometers and protocols. A simplified conceptual formula (often incorporated into the nomogram's derivation) is: VO2 (L/min) = (0.002 x Workload in kpm/min) + 0.1 This formula gives submaximal VO2. To estimate VO2max, you then use the relationship between submaximal HR and maximal HR: Estimated VO2max (L/min) = Submaximal VO2 (L/min) x (220 - Age) / (Test HR) Note: The nomogram inherently incorporates these relationships and is the more direct method for the Astrand test.

• Age Correction Factor:

  • The Astrand nomogram provides an initial estimate of VO2max. However, it assumes a maximal heart rate of 195 bpm. For individuals significantly older or younger than 25 years, an age correction factor should be applied to the initial VO2max estimate from the nomogram.
  • Age Correction Factors:
    • 25 years: 1.00
    • 35 years: 0.87
    • 45 years: 0.78
    • 55 years: 0.73
    • 65 years: 0.69
    • Multiply your estimated VO2max (L/min) by the appropriate age correction factor to get the final age-corrected VO2max.

• Interpreting Your VO2max:

  • Convert L/min to ml/kg/min by multiplying by 1000 and dividing by body weight in kg.
  • Compare your final age-corrected VO2max (ml/kg/min) to normative data tables (often categorized by age and sex) to assess your cardiorespiratory fitness level (e.g., excellent, good, average, fair, poor).

Advantages and Limitations

Advantages:

• Submaximal: Lower risk and less strenuous than maximal tests.
• Ease of Administration: Simple protocol, requires basic equipment.
• Good for Large Groups: Can be administered relatively quickly.
• Reliable: Provides a reasonably reliable estimate of VO2max when performed correctly.

Limitations:

• Estimation: It is an estimate, not a direct measurement, and can have a standard error of 10-15%.
• Assumptions: Relies on several assumptions (e.g., linear HR-VO2 relationship, similar mechanical efficiency across individuals, predicted maximal HR), which may not hold true for everyone.
• External Factors: Heart rate can be influenced by factors other than exercise intensity, such as stress, fatigue, medications, and environmental conditions.
• Cadence Dependence: Maintaining a precise 50 RPM is crucial; deviations can affect accuracy.

Who Should NOT Perform This Test?

While generally safe, the Astrand test is not suitable for everyone. Individuals with the following conditions should NOT perform this test without explicit medical clearance:

• Unstable angina or recent myocardial infarction
• Uncontrolled hypertension (systolic >180 mmHg, diastolic >110 mmHg)
• Significant cardiac arrhythmias
• Acute systemic illness or fever
• Uncontrolled metabolic diseases (e.g., severe diabetes, thyroid dysfunction)
• Acute musculoskeletal injury or pain that would prevent safe cycling
• Pregnancy (unless cleared by a physician and performed with caution)

Conclusion

The Astrand-Rhyming cycle ergometer test remains a valuable, accessible, and practical tool for estimating cardiorespiratory fitness. When administered correctly with proper pre-test considerations and safety protocols, it provides a reliable submaximal assessment of VO2max. Understanding its principles, execution, and interpretation empowers fitness enthusiasts, trainers, and kinesiologists to effectively monitor fitness levels and guide exercise programming, contributing to improved health and performance outcomes.