Assessment of the maximum voluntary arm muscle contraction in sign language for the deaf

The purpose of this study was to investigate the levels of upper member muscles' activation of deaf individuals, who use the Brazilian sign language - LIBRAS, comparing these findings to volunteers with no postural deviations and normal hearing

Forty eight volunteers divided into two groups comprising healthy and deaf subjects (24 volunteers for each group). The signs of rest were obtained with the volunteer maintaining the upper member in an anatomical position, but with the forearm flexed and sustained by the lower member. Maximum voluntary isometric contractions (MVIC) of the biceps, triceps, deltoid, and trapezius muscles were performed in the position of muscular function testing. Statistical analysis was performed using the SPSS-10.0. Continuous data with normal distribution were analyzed by ANOVA with the significance level of p < 0.01.

The normalized electromyographic muscle data obtained in muscular rest do not show statistically significant differences among the studies muscles, in both groups. In the comparison of normalized RMS values obtained in MVIC, the mean values for the trapezius muscle of deaf group were statistically lower than control group.

This study's results indicate there are no differences between the levels of muscular activation for arm biceps, arm triceps, and the anterior portion of the deltoid muscle between the mean normalized RMS values of deaf and healthy individuals.