Heart Rate Dynamics during Localized Upper-Extremity Function as a Novel Measure of Cardiac Autonomic Dysfunction: Investigation of Aging- and Disease-Related Alterations.

Introduction: Cardiac autonomic dysfunction reduces the cardiac system's ability to respond to stressors and is prevalent in aging and diseases, especially cardiovascular diseases like aortic stenosis (AS). Heart rate variability (HRV) is a common measure for evaluating parasympathetic activity and cardiac autonomic function; similarly, heart rate (HR) changes during exercise are utilized in determining cardiac health. However, directly measuring HR parameters from an electrocardiogram (ECG) is difficult due to motion artifacts during exercise.

Sensor-Based Frailty Assessment Using Fitbit.

This study evaluated the reliability of Fitbit in assessing frailty based on motor and heart rate (HR) parameters through a validated upper extremity function (UEF) test, which involves 20 s of rapid elbow flexion. For motor performance, participants completed six trials of full elbow flexion using their right arm, with and without weight. Fitbit and a commercial motion sensor were worn on the right arm.