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Old 02-18-23 | 10:26 AM
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terrymorse
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Converting between Power, VO2, and METs

Putting this here to make it searchable, so when anyone (I) needs to do a conversion, they (I) can find it. Please comment if you think I got something wrong, and I'll update.

These conversions are based on a leg ergometry equation from ACSM's Guidelines for Exercise Testing and Prescription, (a paper book that I am too cheap to buy).

Definitions:
  • MET: Metabolic Equivalent of Task. A common measure used by scientists. One MET unit is roughly the energy expended when sitting quietly, set by convention at an oxygen consumption (VO2) of 3.5 ml/kg/min.
  • VO2: A person's rate of oxygen consumption, typically in units of milliliters per kilogram body mass per minute (ml/kg/min).
  • PWR: Power to Weight Ratio. Power produced at the cranks divided by body mass (watts/kg).

Conversions from PWR (W/kg):
  • VO2 (ml/kg/min) = (10.8 * PWR) + 7
  • METs = 0.286 * VO2 = (3.09 * PWR) + 2
Limitations:
  • steady state sub-maximal aerobic exercise
  • power range 50-200 watts
ACSM Leg Ergometry Equation:




Source: PowerPoint from immagic.com


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UPDATE:

What About Power At VO2max?



Since the ACSM formula is limited to "sub-maximal aerobic effort", it doesn't apply to VO2max.

However, this paper:

Hawley, J. A., & Noakes, T. D. (1992). Peak power output predicts maximal oxygen uptake and performance time in trained cyclists. European journal of applied physiology and occupational physiology, 65(1), 79–83. https://doi.org/10.1007/BF01466278

has a formula for VO2max and peak power, based on a ramped power test, starting at 100 watts and increasing by 25 watts every 150 seconds.

Definitions:
  • Peak Power Output (PPO): highest power achieved (Watts)
  • Body Mass (BM): body mass of cyclist (kg)
  • Peak Power to Weight Ratio (PPWR): PPO divided by BM (W/kg)
  • VO2max: maximum oxygen consumption (ml/min/kg)
Formulas:
  • Calculate VO2max from PPO: VO2max = (1000 / BM) * (0.01141 * PPO + 0.435)
  • Calculate VO2max from PPWR: VO2max = 11.41 * PPWR + (435 / BM)
  • Calculate PPWR from VO2max: PPWR = 0.0876 * VO2max - (38.12 / BM)
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Last edited by terrymorse; 03-05-23 at 08:32 PM.
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