# Estimating V̇O2 max in healthy subjects without maximal effort: a novel protocol using ballistocardiography

## TL;DR

This study shows that ballistocardiography can estimate maximal oxygen uptake without requiring maximal effort, offering a simpler and safer alternative to traditional testing.

## Contribution

A novel protocol using ballistocardiography during submaximal cycling to estimate V̇O2 max without maximal effort.

## Key findings

- BCG-based V̇O2 max estimates achieved accuracy comparable to maximal tests with a 12.05% coefficient of variation.
- Modified protocols with short breaks provided reliable V̇O2 max and workload values similar to standard tests.
- The method requires only 10 minutes of exercise and avoids maximal effort.

## Abstract

Low maximal oxygen uptake (V̇O2 max) is a strong predictor of cardiovascular morbidity and mortality, yet its gold-standard assessment through cardiopulmonary exercise testing (CPET) requires maximal effort and specialized equipment. This study evaluates whether ballistocardiography (BCG), recorded during brief stabilization breaks embedded in a submaximal cycling protocol, can provide reliable estimates of V̇O2 max. BCG provides unique insights into stroke volume and blood displacement, offering a robust physiological basis for V̇O2 max estimation. Sixteen healthy young adults completed three randomized exercise protocols on a cycle ergometer with simultaneous gas-exchange analysis: a standard incremental step CPET until exhaustion (S) and two modified protocols including short breaks (B1 and B2) designed to facilitate high-quality BCG acquisition. BCG-derived kinetic output (KVO2) was used to predict V̇O2 max through a linear regression model based on early-stage workload increments. Both break-based protocols yielded CPET-measured V̇O2 max and maximal workload values comparable to those from the standard test. BCG-based V̇O2 max estimation, using only the first breaks of the protocol, which require a total exercise duration of 10.1 (9.5; 10.8) minutes without reaching maximal effort, demonstrated accuracy comparable to maximal standard tests, with a coefficient of variation of 12.05% and a mean absolute percentage error of 15.59%. While this study was limited to healthy young adults, the proposed approach holds potential for broader applications, particularly in diverse settings or in populations where maximal effort is impractical. Future work should focus on integrating additional BCG signal features and validating these methods in diverse populations.