Åstrand-Ryhming test calculator

What the Åstrand-Ryhming test is

The Åstrand-Ryhming test is a submaximal cycle test, published by Per-Olof Åstrand and Irma Ryhming in 1954, that estimates VO2max from your heart rate at a fixed workload. You never ride to exhaustion. Instead you ride six minutes at a constant, moderate load and the test uses the link between workload, oxygen use and heart rate to predict what your maximum would be.

It is widely used in clinics, occupational health and sports science because it is safe, quick and repeatable. For cyclists it is a useful way to track aerobic fitness in the off-season, after illness or whenever an all-out test is not a good idea. It is part of the free LeCoach cycling calculators.

How to do the test on a bike

You need a bike on a smart trainer in ERG mode (or any ergometer that holds a fixed wattage) and a chest strap heart rate monitor.

1. Choose your workload. Pick a load that brings your heart rate to between 125 and 170 bpm. As a guide: men 50 to 100 W if untrained, 100 to 150 W if you ride regularly; women 50 to 75 W if untrained, 75 to 100 W if you ride regularly.
2. Warm up for 2 to 3 minutes very easily.
3. Ride 6 minutes at the fixed workload, at a steady cadence. The original protocol used 50 rpm on a mechanical ergometer; on a smart trainer in ERG mode any steady cadence you are comfortable with, around 60 to 80 rpm, works. Keep it the same every time you test.
4. Note your heart rate at the end of minute 5 and minute 6. If they differ by more than 5 bpm, your heart rate has not settled yet: ride one more minute and use the last two readings.
5. Check the range. The steady heart rate must be between 125 and 170 bpm. Below that, repeat with a higher load; above it, use a lower load.
6. Enter workload, the two heart rates, your age, sex and weight in the calculator above.

Do the test rested, at least two hours after a meal, without caffeine, in a cool room. Heat, caffeine, stress and fatigue all raise heart rate and make your VO2max read lower.

The formula

The calculator uses the equation form of the original Åstrand-Ryhming nomogram. Workload (W) is converted to kg·m/min (1 W = 6.118 kg·m/min), and HR is your steady-state heart rate:

• Men: VO2max (L/min) = (0.00212 × W + 0.299) ÷ (0.769 × HR − 48.5) × 100
• Women: VO2max (L/min) = (0.00193 × W + 0.326) ÷ (0.769 × HR − 56.1) × 100

Because maximum heart rate falls with age, the result is multiplied by an age correction factor:

Ages in between are interpolated. Finally, litres per minute are divided by body weight to give mL/kg/min.

How accurate is it?

The Åstrand-Ryhming test is a good tool for tracking change in the same person under the same conditions. As a single absolute value it has clear limits:

• It assumes an average maximum heart rate for your age. If your real maximum is much higher than average, the test underestimates your VO2max; if it is lower, it overestimates.
• Trained endurance athletes are often underestimated. The equation was calibrated on young, mostly untrained adults, and it fits very fit riders less well. For fit cyclists with a power meter, the 5-minute power method is usually more accurate.
• Beta blockers and some other medications change heart rate and make the test invalid.
• Day-to-day heart rate varies with sleep, hydration, temperature and stress by several beats, which moves the result.

Typical error for an individual is in the range of 10 to 15 %. That is fine for "am I fitter than three months ago?" and not fine for "is my VO2max 52 or 55?".

When to use this test

• Off-season or base phase, when you want a fitness check without breaking your training rhythm.
• Returning from illness or injury, when an all-out effort is not advised.
• Riders new to structured training, who cannot yet pace a maximal test well.
• Regular check-ins, for example once a month, always with the same workload, the same trainer and at the same time of day. A falling heart rate at the same workload is a clear sign your aerobic fitness is improving, even before you work out VO2max.

If you are fit and own a power meter, the VO2 max calculator with a 5-minute effort gives a better number. If you want to train with heart rate afterwards, set your zones in the heart rate zone calculator.

LeCoach reads your resting heart rate, HRV and sleep from Intervals.icu every morning, so you can see whether a test on a given day reflects your fitness or simply a tired week.