A generalized equation for predicting peak oxygen consumption during treadmill exercise testing: mitigating the bias from total body mass scaling.

Background: Indexing peak oxygen uptake (VOpeak) to total body mass can underestimate cardiorespiratory fitness (CRF) in women, older adults, and individuals with obesity. The primary objective of this multicenter study was to derive and validate a body size-independent scaling metric for VOpeak. This metric was termed exercise body mass (EBM).

Method: In a cohort of apparently healthy individuals from the Fitness Registry and the Importance of Exercise National Database, we derived EBM using multivariable log-normal regression analysis. Subsequently, we developed a novel workload (WL) equation based on speed (Sp), fractional grade (fGr), and heart rate reserve (HRR). The generalized equation for VOpeak can be expressed as VOpeak = Cst × EBM × WL, where Cst is a constant representing the VOpeak equivalent of one metabolic equivalent of task. This generalized equation was externally validated using the Stanford exercise testing (SET) dataset.

Results: A total of 5,618 apparently healthy individuals with a respiratory exchange ratio >1.0 (57% men, mean age 44 ± 13 years) were included. The EBM was expressed as Mass (kg) × Height (m) × 1.16 (if a man) × exp (-0.39 × 10 × age), which was also approximated using simple sex-specific additive equations. Unlike total body mass, EBM provided body size-independent scaling across both sexes and WL categories. The generalized VOpeak equation was expressed as 11 × EBM × [2 + Sp (in mph) × (1.06 + 5.22 × fGr) + 0.019 × HRR] and had an of 0.83,  < 0.001. This generalized equation mitigated bias in VOpeak estimations across age, sex, and body mass index subgroups and was validated in the SET registry, achieving an of 0.84 ( < 0.001).

Conclusions: We derived a generalized equation for measuring VOpeak during treadmill exercise testing using a novel body size-independent scaling metric. This approach significantly reduced biases in CRF estimates across age, sex, and body composition.