Validity and reliability of seismocardiography for the estimation of cardiorespiratory fitness

BACKGROUND: Low cardiorespiratory fitness (ie, peak oxygen consumption [[Formula: see text] O(2)peak]) is associated with cardiovascular disease and all-cause mortality and is recognized as an important clinical tool in the assessment of patients. Cardiopulmonary exercise test (CPET) is the gold standard procedure for determination of [Formula: see text] O(2)peak but has methodological challenges as it is time-consuming and requires specialized equipment and trained professionals. Seismofit is a chest-mounted medical device for estimating [Formula: see text] O(2)peak at rest using seismocardiography. OBJECTIVE: The purpose of this study was to investigate the validity and reliability of Seismofit [Formula: see text] O(2)peak estimation in a healthy population. METHODS: On 3 separate days, 20 participants (10 women) underwent estimations of [Formula: see text] O(2)peak with Seismofit (×2) and Polar Fitness Test (PFT) in randomized order and performed a graded CPET on a cycle ergometer with continuous pulmonary gas exchange measurements. RESULTS: Seismofit [Formula: see text] O(2)peak showed a significant bias of –3.1 ± 2.4 mL·min(–1)·kg(–1) (mean ± 95% confidence interval) and 95% limits of agreement (LoA) of ±10.8 mL·min(–1)·kg(–1) compared to CPET. The mean absolute percentage error (MAPE) was 12.0%. Seismofit [Formula: see text] O(2)peak had a coefficient of variation of 4.5% ± 1.3% and an intraclass correlation coefficient of 0.95 between test days and a bias of 0.0 ± 0.4 mL·min(–1)·kg(–1) with 95% LoA of ±1.6 mL·min(–1)·kg(–1) in test–retest. In addition, Seismofit showed a 2.4 mL·min(–1)·kg(–1) smaller difference in 95% LoA than PFT compared to CPET. CONCLUSION: The Seismofit is highly reliable in its estimation of [Formula: see text] O(2)peak. However, based on the measurement error and MAPE >10%, the Seismofit [Formula: see text] O(2)peak estimation model needs further improvement to be considered for use in clinical settings.