Åstrand-Rhyming Cycle Ergometer VO2 Max Calculator

Calculate your VO2 max

The formula

Åstrand and Rhyming built their model around a nomogram (a paper lookup chart) relating steady-state heart rate and workload to VO2 max. In computational form it is:

where K_sex is a sex-specific constant, the reference HR is 195 bpm for men and 198 bpm for women, and the age correction factor adjusts for the fact that HR_max declines with age (Åstrand's subjects were mostly 20–30). Our calculator handles all arithmetic for you; you only need your workload, steady-state HR, age, sex, and weight.

Protocol

1. Set the ergometer to a workload that will elevate your HR into the 125–170 range. A useful starting guideline: 100 watts for unconditioned women, 150 W for unconditioned men, 150–200 W for trained women, 200–250 W for trained men.
2. Pedal steadily at 50–60 RPM for 6 minutes. Many modern ergometers display wattage directly; on older models, check the resistance-cadence chart. Keep cadence constant — wattage and cadence together determine oxygen demand.
3. Record HR at minute 5 and minute 6. The two readings should be within 5 bpm of each other — that confirms you are in steady state. If they aren't, extend the test by 2 minutes or repeat at the same workload.
4. Take the average of the minute-5 and minute-6 HR as your steady-state HR. Enter it in the calculator along with workload, age, sex, and weight.
5. The result is your estimated VO2 max in ml/kg/min, age-corrected.

If your HR is below 125 at the end of 6 minutes, the workload was too easy — increase resistance by 25–50 W and repeat. Above 170, the workload was too hard; reduce by 25 W.

Why it works: the HR-VO2 line

At submaximal intensities, heart rate rises linearly with oxygen consumption. The slope of that line is roughly the same for all adults; the intercept is shifted up or down by fitness. A fit 30-year-old might produce a VO2 of 2.5 L/min at HR 130; an unfit 30-year-old produces 2.5 L/min at HR 170. Åstrand's insight was that by observing HR at one submaximal workload, you can project the line up to the age-predicted HR_max (roughly 195 for young adults) and read off predicted VO2 max at that intersection.

Accuracy

Correlation with directly measured VO2 max is around r = 0.70–0.85, with a standard error of estimate of roughly 10–15% — less accurate than the Cooper or 1.5-mile run in trained populations but more accurate than most step-test or non-exercise methods.

The main sources of error are:

• Age-predicted HR_max error. The "220 − age" rule has a standard deviation of about 10 bpm — about one-fifth of your HR range. A 10 bpm error in estimated HR_max shifts VO2 max prediction by ~2 ml/kg/min.
• HR drift. In hot environments or dehydrated testers, HR drifts upward at constant power, inflating the apparent VO2 cost and underestimating VO2 max.
• Non-steady-state HR. If you stop the test before 6 minutes or don't verify steady state, HR may still be rising and the formula breaks.

Practical workload selection

If your first attempt lands HR outside 125–170, adjust workload and rest 5 minutes before retesting.

When to use Åstrand-Rhyming

• You have access to a calibrated cycle ergometer. Any gym bike with a wattage display will do; older spin bikes without wattmeters will not.
• You prefer a non-impact test. No running, no joint loading.
• You want a quick submaximal test. 6 minutes of steady pedaling vs. a maximal 12-minute run.

If you want higher accuracy from a cycle test, use the YMCA multistage cycle ergometer instead — it uses two workloads for a personalized HR-VO2 line.

Gear for this test

Steady-state HR accuracy matters — a chest strap gives cleaner readings than wrist optical, especially at the lower end of the HR range. As an Amazon Associate we earn from qualifying purchases.

Frequently asked questions

What is the Åstrand-Rhyming cycle test?

A 6-minute single-stage submaximal cycle ergometer test that estimates VO2 max from steady-state heart rate at a known wattage, adjusted for age and sex. Published by Åstrand and Rhyming in J Appl Physiol, 1954.

How accurate is the Åstrand test?

Correlation with directly measured VO2 max is around r = 0.70–0.85, with a standard error of estimate of roughly 10–15% of the predicted value. Moderate accuracy — better than step tests, less accurate than the Cooper run.

What workload should I use?

Target a steady-state heart rate between 125 and 170 bpm. Typical starting wattages: 75–100 W for unconditioned women, 125–175 W for conditioned women, 100–150 W for unconditioned men, 175–250 W for conditioned men. Adjust after the first attempt if HR lands outside 125–170.

Does cadence matter?

Yes. Keep cadence between 50–60 RPM (Åstrand's original protocol) or use the wattage-display value on a modern ergometer. Wattage and cadence together determine oxygen demand — wildly variable cadence breaks the HR-workload relationship.

Can I use my Peloton or spin bike for this test?

Only if the bike displays calibrated power (watts). Many spin bikes show "resistance" on an arbitrary 1–100 scale that does not map directly to watts. Newer Peloton bikes display true watts and are suitable; older bikes without wattage displays are not.