Which components define the sensor suite known as the Inertial Measurement Unit (IMU) essential for modern posture tracking?

A combination of three-axis accelerometers, gyroscopes, and sometimes magnetometers.

The Inertial Measurement Unit (IMU) represents a significant advancement that powered the explosion in posture monitoring capabilities. An IMU is a sophisticated sensor package designed to track motion and orientation in three-dimensional space. It achieves this by integrating multiple sensor types: three-axis accelerometers measure linear acceleration and gravity's pull; gyroscopes measure angular velocity, which tracks rotation; and often, magnetometers are included to provide an absolute reference direction relative to the Earth's magnetic field. This comprehensive combination allows the device to track orientation accurately, something simpler sensors struggled to achieve reliably, especially during complex user movements.