Development of a 3D workspace shoulder assessment tool incorporating electromyography and an inertial measurement unit—a preliminary study

Abstract

Traditional shoulder range of movement (ROM) measurement tools suffer from inaccuracy or from long experimental setup times. Recently, it has been demonstrated that relatively low-cost wearable inertial measurement unit (IMU) sensors can overcome many of the limitations of traditional motion tracking systems. The aim of this study is to develop and evaluate a single IMU combined with an electromyography (EMG) sensor to monitor the 3D reachable workspace with simultaneous measurement of deltoid muscle activity across the shoulder ROM. Six volunteer subjects with healthy shoulders and one participant with a ‘frozen’ shoulder were recruited to the study. Arm movement in 3D space was plotted in spherical coordinates while the relative EMG intensity of any arm position is presented graphically. The results showed that there was an average ROM surface area of 27291 ± 538 deg2 among all six healthy individuals and a ROM surface area of 13571 ± 308 deg2 for the subject with frozen shoulder. All three sections of the deltoid show greater EMG activity at higher elevation angles. Using such tools enables individuals, surgeons and physiotherapists to measure the maximum envelope of motion in conjunction with muscle activity in order to provide an objective assessment of shoulder performance in the voluntary 3D workspace. Graphical abstractThe aim of this study is to develop and evaluate a single IMU combined with an electromyography (EMG) sensor to monitor the 3D reachable workspace with simultaneous measurement of deltoid muscle activity across the shoulder ROM. The assessment tool consists of an IMU sensor, an EMG sensor, a microcontroller and a Bluetooth module. The assessment tool was attached to subjects arm. Individuals were instructed to move their arms with the elbow fully extended. They were then asked to provide the maximal voluntary elevation envelope of the arm in 3D space in multiple attempts starting from a small movement envelope going to the biggest possible in four consecutive circuits. The results showed that there was an average ROM surface area of 27291 ± 538 deg2 among all six healthy individuals and a ROM surface area of 13571 ± 308 deg2 for the subject with frozen shoulder. All three sections of the deltoid show greater EMG activity at higher elevation angles. Using such tools enables individuals, surgeons and physiotherapists to measure the maximum envelope of motion in conjunction with muscle activity in order to provide an objective assessment of shoulder performance in the voluntary 3D workspace.

Wearable systems for shoulder kinematics assessment: a systematic review

“…Three studies included EMG sensors in their assessment tool in combination with accelerometers [58], IMUs [59] and M-IMU [39]. EMG sensors placed on the biceps, triceps [59] and deltoid muscles [39] provide additional information about upper limb motor function and shoulder assessment, evaluating muscles activity. Quantification of upper limb motion was executed through a wearable device, MYO armband by Thalamic labs, that combines EMG sensors to record electrical impulses of the muscles [7, 87].…”

Movement Analysis with Inertial Measurement Unit Sensor After Surgical Treatment for Distal Radius Fractures

“…Some studies have demonstrated a direct relationship between muscle activity amplitude and pain. 25 Aslani et al 26 reported the study of shoulder ROM with a single IMU combined with an EMG sensor to monitor the 3D reachable workspace with simultaneous measurement of deltoid muscle activity, showing that shoulder disorders may be assessed in terms of 3D surface area and with EMG.…”

Assessment of mobility deficit and treatment efficacy in adhesive capsulitis by measurement of kinematic parameters using IMU sensors

“…Usually, the most common measurement tools for clinical evaluation of shoulder performance are mechanical manual systems such as the goniometer, inclinometer and plurimeter. However, mechanical measurement tools have some limitations and provide little information about the quality of movements or the ability to carry out functional tasks [13], [14].…”

“…Other valid systems used for human motion analysis include vision-based systems and optoelectronic systems. However, they are relatively expensive and restricted to laboratory settings, and require specific technical expertise [13], [14]. On the other hand, the inertial sensors offer practical alternatives relatively cheaper and portable for kinematic and functional assessment.…”