Van Hooren B; Institute of Nutrition and Translational Research in Metabolism (NUTRIM), Maastricht, the Netherlands.
Souren T; Miqueu F; Bongers BC

Scandinavian Journal of Medicine & Science in Sports. 36(1):e70184, 2026 Jan.

The validity and between-day reliability of cardiopulmonary exercise
testing (CPET) systems remain largely unexplored. We therefore evaluate
the validity and between-day technological and biological reliability of
five popular CPET systems for assessing respiratory variables, substrate
use, and energy expenditure during simulated and real human exercise. The
following systems were assessed: Vyntus CPX, Oxycon Pro, VO2 Master, KORR,
and Calibre. A metabolic simulator was used to simulate breath-by-breath
gas exchange. The values measured by each system (minute ventilation (VE),
breathing frequency (BF), oxygen uptake (VO2), carbon dioxide production
(VCO2), respiratory exchange ratio (RER), energy from carbohydrates and
fats, and total energy expenditure) were compared to the simulated values
to assess the validity. Six well-trained participants cycled 5% below
their first ventilatory threshold on 2 days to verify the validity in
human exercise. Between-session reliability was assessed in both the
simulation and human experiments to determine technological and biological
variability. Absolute percentage errors during the simulations ranged from
0.69% to 5.56% for VE, 0.92% to 1.44% for BF, 3.12% to 7.86% for VO2,
4.07% to 12.1% for VCO2, 1.21% to 6.94% for RER, 2.83% to 48.8% for Kcal
from carbohydrates, 14.1% to 50.3% for Kcal from fats, and 4.21% to 6.98%
for total energy expenditure. Between-session variability during
simulation (i.e., technological variability) ranged from 0.46% to 3.15%
for VO2 and 0.71% to 4.99% for VCO2. The error and between-day variability
of the error for respiratory gas variables, substrate, and energy use
differed substantially between systems. Biological and technological VO2
and VCO2 variability, respectively, accounted for ~60%-70% and 40%-30% of
the variability in repeated human testing.