Atividade elétrica dos músculos estabilizadores da patela em indivíduos portadores da síndrome da dor femoropatelar durante exercícios realizados no step.

Abstract

The purpose of this study was to evaluate the electric activity (EMG) in the temporal and amplitude aspects of the vastus medialis obliquus (VMO), vastus lateralis longus (VLL) and vastus lateralis obliquus (VLO) muscles during forward step tasks: stepdown (SFD) and step-up (SFS), and backward step tasks: step-down (SPD) and step-up (SPS). Twenty seven females were evaluated and separated in two groups: fifteen normal subjects Control Group (21.13 ± 2.17 years) and twelve subjects with Patellofemoral Pain Syndrome PPS (21.08 ± 2.31 years). The height of the step was regulated for two angles 45º and 75º - of knee s flexion joint. A metronome was used to help the volunteers about the time to performance the tasks, a eletrogoniometer was used in the control of the knee angle and a pressure sensor was used to determinate the start and the end of the electromyography register. The electric activity was recorded by surface (Ag/AgCl) electrodes, an EMG apparatus with 8 channels (EMG System Brazil) and a software of acquisition data AqDados 7.02. The EMG data was processed by the software Matlab 6.1 that calculated both the onset timing of the muscles and the integrated of the EMG signal. The EMG was normalized by the mean of the three muscle contractions and was calculated de ratio VMO/VLL and VMO/VLO for comparisons between groups and exercises. The relative onset timing was determinate by the difference VMO-VLO and VMO-VLL. The t-tests showed that in the step up exercise (75º of the knee flexion), there are differences when compared the groups, either in frontal step VMO/VLL (p= 0.000) and VMO/VLO (p = 0.000), than posterior step VMO/VLL (p = 0.000) and VMO/VLO (p = 0.000). In the control group there is a prevalence of an early contractions of de VMO muscle, however in the PPS group, the VMO onset occurred at the same time or after the VLO and VLL muscles in the mayor of the cases. The Anova three-way and Duncan post hoc showed that in step at 45º, the ratio VMO/VLO (p = 0,000) and VMO/VLL (p = 0,016) was greater then step at 75º in both groups. When compared the steps in 45º and 75º into the groups, were found differences either in the VMO:VLO ratio (p = 0,000) than VMO:VLL ratio (0,016) with greater values in the step at 45º. The comparison between the exercises performed in the same step height showed that both VMO:VLO and VMO:VLL ratios always was greater in the SFS than SFD (p = 0,01), SPS (p = 0,04) and SPD (p = 0,000). There is no difference between SFD and SPS (p = 0,570) or SPD (p = 0,090). In the Control group the SPS was smaller then SPD, on the other hand, in the SDFP group the SPS was greater than SPD (p = 0,30). Our results suggest that there is a difference in the motor control between groups about muscle recruitment either in frontal than posterior step-up at 75º. In the amplitude aspect, the step at 45º seem to recruit selectively the VMO muscle in comparison with VLL and VLO, thus, this step height should be used preferentially in the SDFP treatment programs. Regarding of the mode of execution, the frontal step (SFS) seems to be the most indicated when the objective is the selective activation of the VMO muscle mainly in the step at 45º.