Test-retest variability of VO2max executed with the Omnical shows a linear relationship of VO2 and Power in a cardiopulmonary exercise test.

The VO2max is the maximal capacity of the cardiovascular system to provide O2 to the active muscles and the capacity to use O2 during continuous exercise. A high VO2max is negatively correlated with the risk of developing cardiovascular diseases and mortality and the VO2max is considered the gold standard of cardiovascular fitness.

Mostly the VO2max is measured by a breath-by-breath analysis, but this has a couple disadvantages:

  1. The response time of the O2 analyzers is lower than the physiological maximum of the athlete.
  2. When the breathing frequency increases, the analysis becomes more inaccurate.

A total capture or free flow indirect calorimeter captures and analyses the exhalation fully and can complete a normal standardized validation without restrictions or specialized equipment.

The study:

In a recent study by Schoffelen et al. the Omnical has been validated for both technical accuracy and biological reproducibility against a breath-by-breath system. The results show that the Omnical has a smaller variation in the measured VO2– and VCO2– values, than the breath-by-breath analysis. This indicates that the Omnical can achieve a high degree of technically validated accuracy over the full range of human energy expenditure.


The VO2max– and Pmax– results, measured by the Omnical, show a low intra-individual variability and almost perfect linearity. This implies that human maximal performance is reproducible and linearly associated with Pmax over the entire range of P and VO2. The demonstration of this effect would not be possible without the high accuracy of the Omnical system.

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Schoffelen PFM, den Hoed M, van Breda E, Plasqui G. Test-retest variability of VO2max using total-capture indirect calorimetry reveals linear relationship of VO2 and Power. Scand J Med Sci Sports. 2019 Feb;29(2):213-222. doi: 10.1111/sms.13324. Epub 2018 Nov 12.