I am trying to understand how to use Swain HR to Power equation in my case. Here is a calculator where one can vary the inputs and see the various outputs based based on the equation: http://www.cyclingpowerlab.com/VO2maxPowerRelationship.aspx

Suppose my 20min HR is 183bpm and 20min Power is 280W. If I select an efficiency of 22% and set VO2Max to 4300ml the HR and Power align, 183bpm vs 280W, also another point on the graph is aligned for me and that is 171bpm with 250W.

Is this the right way to use equation or I should have data from a 1h test?


  • 1
    Can you clarify your question? The Swain model is used to estimate power when you know heart rate, VO2Max, and metabolic efficiency. You appear to have power and HR. Are you trying to go backwards to estimate VO2Max, or metabolic efficiency, or something else? – R. Chung Jul 10 '15 at 15:32
  • I had the impression that Swain gives a relation between VO2 consumption and HR. So we go from Power to VO2 and use both VO2 and HR to estimate VO2Max. So yes this is what I am after, estimating VO2Max from HR and power data. – Bogdan Petrica Jul 10 '15 at 17:50
  • The missing part here is the efficiency, but I try to select an efficiency so two data points on the Swain function match. – Bogdan Petrica Jul 10 '15 at 17:54
  • 3
    Ah, okay. The issue is that even if you have HR, you don't have stroke volume which is what you need to get cardiac output. However, if you know metabolic efficiency (net or delta or work efficiency are better than gross efficiency, but sometimes all you have is gross efficiency) you can go from work to get L of O2 consumed, so if you have total mass you can estimate VO2Max. So you don't really need HR -- Swain was using that because he didn't have power, but you do. So do a VO2Max-level power effort and convert directly to estimate VO2Max. – R. Chung Jul 10 '15 at 18:15
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    Exactly, though you'll want to exhaust your anaerobic capacity or else you'll overestimate VO2Max. That's why VO2Max tests are usually done with a ramped protocol, and the estimates are done off the final step before failure. In your example, you don't want to use the average of 97kJ for 5 minutes, instead you might want to use the max power over the last minute of a ramped protocol (or another similar protocol where you've exhausted the anaerobic component). – R. Chung Jul 10 '15 at 20:31

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