OBJECTIVE: To investigate the reflex response time (RRT) of the vastus medialis obliquus (VMO), vastus lateralis obliquus (VLO) and vastus lateralis longus (VLL) muscles in clinically healthy individuals and subjects with patellofemoral pain syndrome (PPS). METHODS: Twelve clinically health women and twelve women with PPS were evaluated. Electromyography (EMG) records were obtained using active electrodes connected to an electromyograph that was activated by an external sensor attached to the medial portion of the patella ligament, by means of percussion. The RRT was analyzed by measuring the time, in seconds, between zero and peak electrical response of the VMO, VLO and VLL muscles, for both groups. The statistical analysis consisted of analysis of variance (ANOVA, p< 0.05) and the Tukey post-hoc test (p< 0.05) to compare the response between muscles, and Student's t test (p< 0.05) to compare the response between groups. RESULTS: Both groups presented lower RRT for the VMO muscle than for the VLO and VLL muscles. However, no significant difference was seen between the VLO and VLL muscles. There was no significant difference in RRT between the groups. CONCLUSIONS: According to these results, it can be suggested that the RRTs in the different portions of the quadriceps muscle do not distinguish between subjects with PPS and clinically healthy individuals. The RRT for the VMO muscle was lower than the RRT for the VLO and VLL muscles, for both groups.
patellofemoral pain syndrome; response time; electromyography
