Joint angle-based EMG amplitude calibration.

Area of Science:

• Biomechanics
• Neuroscience
• Biomedical Engineering

Background:

• Surface electromyogram (SEMG) amplitude is affected by joint angles due to muscle displacement under electrodes.
• This variation complicates accurate force prediction from SEMG during constant force tasks.
• Existing methods may not fully account for these biomechanical changes.

Purpose of the Study:

• To develop and validate a calibration method for SEMG signals from the biceps brachii.
• To compensate for amplitude variations caused by changes in muscle position relative to EMG electrodes.
• To improve the accuracy of SEMG-based force estimation models.

Main Methods:

• An experimental protocol was designed to collect SEMG and force data from the biceps brachii.
• Five subjects participated, performing tasks involving constant force levels at various joint angles.
• The fast orthogonal search (FOS) algorithm was employed to establish a relationship between SEMG and wrist-recorded force.

Main Results:

• A novel calibration method was proposed and tested.
• Models trained using calibrated SEMG signals demonstrated statistically significant improvements in evaluation metrics.
• The calibration effectively compensated for SEMG amplitude fluctuations due to joint angle variations.

Conclusions:

• The proposed SEMG calibration method accurately compensates for joint angle-induced amplitude changes.
• Calibrated SEMG signals lead to superior performance in muscle force prediction models.
• This technique enhances the reliability of SEMG for biomechanical and clinical applications.