Diferenças entre os sexos no controle sensório-motor do ombro

Abstract

Sex is an biological risk factor that deserves attention because of its repercussion on the development of work-related musculoskeletal disorders. The prevalence of these disorders is higher among females than among males, especially on the neck/shoulder region. Considering the role of muscle action in shoulder joint function, the integrity of sensorimotor control is important. Therefore, the study of sex differences in sensorimotor control mechanisms contributes for understanding the risks faced by females. This dissertation is composed by a study aiming to investigate if there are sex differences in torque steadiness, amplitude, and variability of activation of the shoulder girdle muscles during isometric shoulder scaption. Seventeen females and 17 without disorders in the neck/shoulder region participated. Torque steadiness was evaluated at 20% and 35% of peak torque. Surface electromyographic signals (sEMG) of the trapezius (all portions), serratus anterior, and anterior deltoid muscles were recorded during steadiness evaluation. Standard deviation (SD), coefficient of variation (CV), stability time and median frequency (MF) of torque were calculated from the steadiness trials. The root mean square (RMS) values of normalized (norm) sEMG for maximum isometric shoulder scaptions were considered for calculation of the SDnorm, CVnorm and MF values. The amplitude of muscle activation was expressed by mean RMSnorm value. The variability of muscle activation was assessed through both SDnorm and CVnorm values from the signals. Females presented lower SD and MF values of torque than males in both targets, indicating that their torque fluctuations were lower and less frequent. Females presented higher RMSnorm and SDnorm values than males for most of the evaluated muscles, that is, they had higher amplitude and variability in muscle activation. The lower and less frequent torque fluctuations and the highest amplitude in muscle activation may expose females to the highest risk of musculoskeletal disorders.