VO2max (Astrand Step Test) Calculator

How it is calculated

The tool turns the steady-state heart rate at the end of the step test into absolute oxygen uptake in L/min. Men: VO2 = 3.744 × (weight + 5) ÷ (HR − 62). Women: VO2 = 3.750 × (weight + 5) ÷ (HR − 65). Weight is in kg and HR in beats per minute. The result is multiplied by an age factor from a table (1.10 at 15, 1.00 at 25, 0.87 at 35, 0.78 at 45, 0.65 at 65, interpolated in between and held constant outside 15–65). The corrected L/min is divided by body weight for mL/kg/min and by 3.5 for METs. Weight must be 25–250 kg and age 10–90. The heart rate must be more than 5 above the sex constant (above 67 for men, 70 for women) and at most 220, and a relative VO2max above 100 mL/kg/min is rejected as impossible. There are no step-height or cadence inputs.

Common mistakes

• Entering a heart rate before it has settled. The formula assumes a steady-state value, so a pulse from the first minute misrepresents the effort and gives a wrong VO2max.
• Looking for step height or stepping rate in the form. Neither is used; the result depends on weight, heart rate, sex and age only.
• Entering weight in pounds. The field expects kg: 165 instead of 75 more than doubles the absolute figure to 7.63 L/min, and the relative value (46.2) no longer matches.
• Choosing the wrong sex. The constants and the HR offset differ (62 for men, 65 for women), so the same pulse gives different answers.
• Entering a resting-like heart rate. A pulse such as 90 bpm for a 75 kg man would imply a VO2max above 100 mL/kg/min, so the tool shows no result; a real steady-state step test gives a much higher pulse.