Handgrip strength test: a study of myoelectric fatigue of flexor carpi radialis and the flexor digitorum superficialis

Abstract

A test protocol of handgrip strength in steps was used in order to study the fatigue of the flexor carpi radialis (FRC) and the flexor digitorum superficialis (FSD) muscles with signal processing in the time and frequency domains. It was used an electronic hand grip dynamometer, and a 16-bits analog-digital converter. The sampling frequency was 2 kHz. The study included 12 healthy subjects, active and right-handed, mean age 21.53 ± 1.26 years, body fat percentage 7.76 ± 3.53%, weight 74.9 ± 10.36 kg and height 180. 69 ± 7.14 cm. The subjects performed the test of maximal voluntary contraction (CIVM) of the dominant hand and then, submaximal protocol of ten seconds steps of 20%, 40% and 60% of CIVM. The proposed test didn't generate a drop on strength performance on the established submaximal steps, as well as the fatigue process establishment of FSD. On the other hand, the FRC showed myoelectric fatigue signs, suggesting stabilizing wrist collapse. These data suggest that myoelectric fatigue of the finger flexors during handgrip is a late process compared to wrist stabilizing fatigue. The protocol in 60% step seems to trigger the myoelectric fatigue muscle process of the FRC but not the FSD, based on analysis of muscle activation in time and frequency domains.