Motor control study in the ascending and descending phases of the squat in subjects with and without patellofemoral pain syndrome (PFPS) / Estudo do controle motor nas fases ascendente e descendente do agachamento em sujeitos saudaveis e portadores da sindrome da dor femoro-patelar (SDFP)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

The patellofemoral pain syndrome (PFPS) affects one in four people in the general population, and is composed of several lesions of the patellofemoral joint. The physical therapy is essential for the rehabilitation of the population with this syndrome, and one of its main tools is the training in closed kinetic chain. Among the several ways of performing that training, the squat is one of the most used. However, when performing it, a person does not always have a proper control of the position of the trunk and of the limbs, what can produce different kinematic, kinetic and electromyographic patterns. Therefore, the present study had as an objective identifying and describing the kinetic and electromyographic strategy used to perform the squat in the ascending and descending phases by people with and without PFPS, when the movements are restricted in the sagittal plane, with a similar kinematic pattern in most of the involved joints. Eight healthy subjects and eight with PFPS participated in this study and they performed the squat keeping the upper arm elevated at 90º at the shoulder joint, just in front of the body in two distances, semisquatting (30º to 50º) and half squatting (60º to 80º) in the descending phase. For the ascending phase they performed the ascent from the half squatting. The electromyographic activity of the vastus medialis oblique, vastus medialis longus, rectus femoris, vastus lateralis, biceps femoris, semitendineous, gastrocnemius lateralis and tibialis anterior muscles was registered. The joint kinematics of the inferior limbs was reconstructed using an optical system for movement analysis. The center of the pressure (COP) was obtained using data from a force plate and the joint torques in the ankle and knee were calculated using inverse dynamics. The tasks were effective in restricting the movement in the cefalo-caudal direction for both groups. Moreover, it was possible to identify and to describe a clear strategy for both the ascending and the descending phases of the squat. The anterior tibialis muscle was the responsible for beginning the squatting in the descending phase, and kept co-activated with the gastrocnemius during the whole movement. The quadriceps was mainly responsible for decelerating the movement and there was not great activity of the hamstrings. Compared to the control group, the PFPS group presented smaller knee torque and smaller quadriceps electromyographic activity, but the ankle torque and the COP displacement to the anterior direction were larger in the two distances, in the descending phase of the squatting. For the ascending phase of the squatting the PFPS group presented difference in the initial position, revealing a protecting strategy for the patellofemoral joint. Before beginning the movement, there was a strong activation of the quadriceps, hamstrings and gastrocnemius. This was necessary for the motor control system to generate the forces that overcome the inertia of the limb and resist the flexion force acting on the knee due to gravity in both groups. Compared to the control group, the PFPS group presented smaller torque in the knee and smaller electromyographic activity of the quadriceps, but the ankle torque and the COP displacement to the anterior direction were larger. The phases of each task were described and clinical implications were discussed. Key words: torque, center of the pressure, electromyographic activity, patella, squat

ASSUNTO(S)

torque patella patela eletromiografia electromyographyc activity

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