Estimate VO₂max from a six-minute submaximal cycle test using workload and steady-state heart rate. The result is a prediction, not a direct measurement of oxygen uptake.
Calculate Estimated VO₂max
Protocol check: this calculator is intended for the Åstrand–Ryhming single-stage cycle test. The traditional protocol uses a constant workload, 50 rpm and a steady-state HR typically within about 125–170 bpm near the end of the test.
Åstrand–Ryhming Test Protocol
- Use a calibrated cycle ergometer and heart-rate monitor.
- After an appropriate warm-up, select a constant workload designed to produce a submaximal steady-state heart rate.
- Maintain approximately 50 revolutions per minute for six minutes.
- Record heart rate each minute. The final two readings should be close enough to indicate a steady response; a difference of no more than about 5 bpm is commonly used.
- Use the steady-state heart rate and workload to estimate VO₂max, then apply the age correction used by the traditional Åstrand method.
When the Calculator Should Not Be Used
- Different cycle protocol: YMCA, Ekblom–Bak and other submaximal tests use different procedures and prediction methods.
- No steady-state HR: if heart rate is still drifting substantially, the assumptions behind the estimate are weakened.
- Heart-rate-altering medication or conditions: beta-blockers and other factors that alter the normal HR–workload response can invalidate a heart-rate-based prediction.
- Outside the traditional age-correction range: this calculator intentionally limits age entry to 15–65 rather than extrapolating beyond the published correction table.
How the Calculation Works
The calculator uses sex-specific equations that approximate the Åstrand–Ryhming nomogram from workload and steady-state heart rate. Work entered in watts is converted to kg·m/min using 1 W ≈ 6.12 kg·m/min. The resulting absolute VO₂max estimate is multiplied by the traditional age-correction factor and then divided by body mass to give ml/kg/min.
Evidence and Limitations
Åstrand and Ryhming introduced the submaximal nomogram in 1954. Large modern datasets still use the Åstrand test, but validation studies show that individual prediction error can be substantial even when the method is useful at group level. Treat the result as an estimate suitable for standardised fitness assessment, not as a substitute for directly measured VO₂max.
References: Åstrand PO, Ryhming I. A nomogram for calculation of aerobic capacity (physical fitness) from pulse rate during sub-maximal work. J Appl Physiol. 1954;7:218–221. The sex-specific formula approximation is commonly attributed to Buono and colleagues and is used in published modern research.
Equipment and Related Tools
For suitable laboratory cycling equipment, see our Cycle Ergometer Buyer’s Guide and Monark Exercise Bicycle guide. For other aerobic estimates, use the Bruce, Balke, Rockport or 1.5-Mile Run calculators.
From one cycle test to repeat assessment
The free calculator stays useful on its own. Cartwright Assess adds the professional workflow around repeated assessments, optional participant records, anonymous assessments, PDF reporting and team access.