Accelerocardiogram
Determine heart rate by movements of the rib cage
Author:
Title 4
Learning objectives :
This activity allows students to visualize heartbeats through small movements detectable by the accelerometer. It establishes a concrete link between technology and physiology.
Concepts covered
Cardiac physiology, Accelerometer movement detection, Frequency and rhythm, Relationships between physical activity and heart rate, Data measurement and analysis
What students will do :
The student places their smartphone on their chest and uses the accelerometer to detect movements caused by heartbeats. By analyzing the resulting graph, it identifies the heart rate at rest, then after physical activity. The student can also try to identify secondary peaks corresponding to the different phases of the cardiac cycle.
What is required :
Smartphone with the FizziQ application, Flat surface for lying down
Scientific background :
The accelerometer of a smartphone can detect accelerations less than 0.01 m/s² with a sampling frequency greater than 100 Hz. When the heart beats, it causes very slight movements of the rib cage which can be captured by this device. These movements correspond to the cardiac cycle: systole (ventricular contraction propelling the blood) and diastole (relaxation allowing the filling of the ventricles). The heartbeat creates a pressure wave that propagates throughout the body and generates tissue movement of just a few millimeters. The accelerometer, placed perpendicular to the chest, detects these variations by converting them into an electrical signal. This technique, called ballistocardiography, was historically performed with complex medical equipment, but modern smartphones now make it simple to perform. The normal resting heart rate varies between 60 and 100 beats per minute in adults (higher in children), and can increase significantly during physical exertion.