ARE FORCE STEADINESS DEFICITS A FEATURE OF WOMEN WITH PATELLOFEMORAL PAIN?

Abstract

BACKGROUND: Task retraining has been widely researched in patellofemoral pain (PFP), it usually involves visual and verbal feedback while executing a specific task. Some studies suggest mechanisms associated with PFP, such as kinematics parameters (hip adduction) and clinical parameters (pain and function), are modifiable using motor retraining techniques. However, it is unknown whether individuals with musculoskeletal disorders, such as PFP, are able to respond properly to a task with visual and verbal feedback from the point of view of motor control mechanisms. AIMS: To evaluate the variation of electromyography activity (coefficient of variation of the gluteus medius - GM; vastus lateralis - VL; and vastus medialis - VM muscles) and torque (coefficient of variation) produced by knee extensors and hip abductors during two tasks (one for each muscle group) of force steadiness at 10% of maximal voluntary isometric contraction (MVIC) with verbal and visual feedback in women with and without PFP. METHODS: Ten females with PFP and 10 females without PFP (asymptomatic) will undergo a baseline assessment, including demographic information as age, height, body mass, duration of symptoms and worst pain level on the previous month. After that, participants will perform MVIC of the knee extensor and hip abductor muscles on an isokinetic dynamometer. After assessment of MVIC tests, isometric steadiness of knee extensors and hip abductors will be measured during 20 seconds at 10% of MVIC. Participants will be instructed to maintain the contraction at 10% of MVIC, verbal and visual feedback will be provided during contractions. Force steadiness and surface electromyography will be compared between groups (PFP group and control group) using an independent t-test.