Abbaspour Kaboudan F;  Veterans Affairs Health Care System, San Francisco, USA
Zeng S; Abrham Y; Roman J; et al

Medicine & Science in Sports & Exercise. 58(11):2570-2580, 2026 Nov 01.

PURPOSE: Volume of oxygen uptake at peak exercise ( ) is a key indicator
of cardiorespiratory fitness used to assess surgical risk and clinical
trial outcomes. However, multiple prediction equations exist for its
interpretation, often yielding inconsistent classifications of exercise
performance. We aimed to determine how different prediction equations
affect exercise performance classification and identify factors
contributing to its variability.

METHODS: We performed a post hoc analysis of cardiopulmonary exercise
testing (CPET) data collected from 332 nonsmoking flight attendants who
participated in our previous studies examining the health effects of
occupational exposure to secondhand tobacco smoke. Percent-predicted was
calculated using seven prediction equations (Fitness Registry and the
Importance of Exercise National Database, Wasserman, Hansen-Wasserman,
Study of Health in Pomerania, Jones, Bruce, and Cooper-Storer). Reduced
exercise performance was defined as < 80 percent-predicted. Agreement
across equations was assessed using Cohen’s kappa. Associations with
dyspnea (modified Medical Research Council >= 1) were examined using
C-statistics to assess the discriminative performance of prediction
equations for this patient-centered outcome. The magnitude of change in
percent-predicted when switching from one equation to another
(“recalculation magnitude”) was quantified for individual participants,
and multivariable regression modeling was used to identify demographic and
anthropometric determinants of recalculation magnitude.

RESULTS: Participants were 56 +/- 12 years old, 86% female, with body
mass index = 24 +/- 4 kg/m 2 . Depending on the prediction equation, mean
percent-predicted varied widely (83%-113%), and the prevalence of reduced
exercise performance ranged from 7% to 51%. Agreement across equations
ranged from slight to substantial (kappa = 0.10-0.79). At an individual
level, switching between equations recalculated percent-predicted by -93%
to +84%, leading to bidirectional exercise performance reclassification of
6.6%-45.5% of participants. Body mass index was the strongest determinant
of recalculation magnitude, followed by age and sex. The discrimination
accuracy of prediction equations for dyspnea was modest (area under the
curve = 0.56-0.71), with the Study of Health in Pomerania equation showing
the best performance.

CONCLUSIONS: Different prediction equations yielded materially different
percent-predicted values and frequently changed exercise capacity
classification in a bidirectional manner. The observed discordance appears
to arise in substantial part from limitations in how demographic and
anthropometric factors, particularly body size, are modeled across
equations, underscoring the need for improved reference standards that
better capture physiological variability.