Comparison of cocontraction methods of forearm muscles for controlling myoelectric prosthetic hand: An experimental study using surface electromyography on healthy participants.

Background: Cocontraction of the extensor carpi radialis longus (ECRL) and flexor carpi ulnaris muscles used to control a transradial myoelectric prosthetic hand. The methods used to generate cocontractions include finger snap, quick spread, and quick fist.

Purpose: This study aimed to identify the most efficient cocontraction-induction method based on electromyographic characteristics by measuring surface electromyography during three cocontraction-induction methods commonly used for transradial myoelectric prosthetic hands in healthy participants.

Study design: This was a cross-sectional study of a convenience sample of healthy adults.

Methods: Myoelectrical action potentials of the ECRL and flexor carpi ulnaris were recorded using a wireless surface electromyograph during three cocontraction methods in 29 healthy university students. The obtained electromyographies of the (1) time difference at the peak of muscle contraction, (2) time to the peak of muscle contraction, (3) duration of muscle contraction, and (4) maximal muscle activity (% root mean square) of both muscles were compared among the three cocontraction methods.

Results: The time difference at the peak muscle contraction and the time to the peak muscle contraction of both muscles were significantly higher in the finger-snap method than in the other methods. The duration of ECRL contraction during the finger snap was also the highest. In contrast, the maximal muscle activity of the finger-snap method was the lowest.

Conclusions: The quick spread and fist are the recommended cocontraction methods for the control of the myoelectric prosthetic hand over the finger snap because the time lag at the peak of muscle contraction and the time to the peak of muscle contraction were significantly lower.