Electromyographic parameters reproducibility after a joint stress protocol in women with patellofemoral pain

The objective of this study was to verify the reproducibility of a joint stress protocol previously to the electromyographic evaluations in subjects with PFD. Twenty women with PFD where evaluated through presence of pain, questionnaires, specific clinical tests for PFD, and superficial electromyography of the muscles vastus lateralis (VL), vastus medialis (VM), and gluteus medius (GM), during free squat and squat associated with isometric hip abduction. The stress protocol was composed of six up and down stairs, three series of road jumps, and five series of eight repetitions of 90º squat with 20% of body weight load. The protocol showed a reproducibility of knee extensors strength, root mean square (RMS) of VL during free squat, and co-activation of VM and GM on squat with hip abduction. In addition, there was a lower variability of the data when the stress protocol was performed.