Validity and reliability of seismocardiography for the estimation of cardiorespiratory fitness

BACKGROUND: Low cardiorespiratory fitness (ie, peak oxygen consumption [V.O2peak]) 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 V.O2peak 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 V.O2peak at rest using seismocardiography.OBJECTIVE: The purpose of this study was to investigate the validity and reliability of Seismofit V.O2peak estimation in a healthy population.METHODS: On 3 separate days, 20 participants (10 women) underwent estimations of V.O2peak 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 V.O2peak 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 V.O2peak 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 V.O2peak. However, based on the measurement error and MAPE &gt;10%, the Seismofit V.O2peak estimation model needs further improvement to be considered for use in clinical settings.</p

Extreme duration exercise affects old and younger men differently

AIM & METHODS: Extreme endurance exercise provides a valuable research model for understanding the adaptive metabolic response of older and younger individuals to intense physical activity. Here, we compare a wide range of metabolic and physiologic parameters in two cohorts of seven trained men, age 30 ± 5 years or age 65 ± 6 years, before and after the participants travelled ≈3000 km by bicycle over 15 days. RESULTS: Over the 15‐day exercise intervention, participants lost 2–3 kg fat mass with no significant change in body weight. V̇O(2)max did not change in younger cyclists, but decreased (p = 0.06) in the older cohort. The resting plasma FFA concentration decreased markedly in both groups, and plasma glucose increased in the younger group. In the older cohort, plasma LDL‐cholesterol and plasma triglyceride decreased. In skeletal muscle, fat transporters CD36 and FABPm remained unchanged. The glucose handling proteins GLUT4 and SNAP23 increased in both groups. Mitochondrial ROS production decreased in both groups, and ADP sensitivity increased in skeletal muscle in the older but not in the younger cohort. CONCLUSION: In summary, these data suggest that older but not younger individuals experience a negative adaptive response affecting cardiovascular function in response to extreme endurance exercise, while a positive response to the same exercise intervention is observed in peripheral tissues in younger and older men. The results also suggest that the adaptive thresholds differ in younger and old men, and this difference primarily affects central cardiovascular functions in older men after extreme endurance exercise