Seismocardiography for nonexercise estimation of cardiorespiratory fitness in older adults

Introduction Cardiorespiratory fitness predicts health and longevity. The gold-standard test for V̇O₂-peak, the cardiopulmonary exercise test (CPET), is difficult to conduct in older adults, and alternative methods offer low to moderate accuracy. This project compared a new method, seismocardiography, to CPET in older adults. It was hypothesized that seismographic V̇O₂-peak estimates would strongly correlate with CPET-derived V̇O₂-peak. Method: Thirty-six healthy older adults (aged 65–75 years; 19 female) completed the seismocardiography assessment (Seismofit ® ) of resting V̇O₂-peak and a CPET on a cycle ergometer. Two criteria were used to support the attainment of maximal oxygen uptake (V̇O₂-peak) during the ramp exercise test: (1) a V̇O₂ plateau, defined as an increase in oxygen uptake of less than 150 mL·min⁻¹ despite a further increase in work rate during the final phase of the incremental protocol, and (2) a respiratory exchange ratio (RER) > 1.15. The V̇O₂-peak estimation at rest was performed over 40 s with participants lying supine while wearing a Seismofit ® chest sensor (VentriJect, Hellerup, Denmark). Concordance between measurements was assessed using correlations and Bland-Altman plots, and paired t-test evaluated mean differences between Seismofit and CPET-derived V̇O₂-peak. Results The sample had a mean age of 70 ± 3.0 years and BMI of 25.7 ± 2.8 kg/m². For all participants, a significant positive correlation was observed between Seismofit ® and measured V̇O₂-peak ( r = 0.57, p < 0.001). When restricting the analysis to the 27 participants with validated V̇O₂-peak, a strong significant positive association between the methods was found ( r = 0.80, p < 0.001). For all participants, Seismofit significantly overestimated V̇O₂-peak (t = 4.48, df = 35, p < 0.001). Conclusion This study demonstrated that Seismofit show a moderate-to-strong association with CPET measurements in older adults. Seismofit, however, systematically overestimated V̇O₂-peak. For Seismofit to be integrated into large-scale cohort studies and experimental research, the methodology used for older adults needs further development.