RESUMO
The purpose of the study was to test the hypothesis on whether individuals with patellofemoral pain syndrome (PFPS) try to avoid knee position during upward squatting so as not to aggravate this syndrome. Also, we tested whether PFPS would generate changes in the kinetic and electromyographic (EMG) strategies used to perform this task. Eight healthy subjects and 8 subjects with PFPS, but without a history of pain for at least 30 days, took part in the experiment. They were asked to perform upward squatting with knees initially flexed at 60° (very flexed) until reaching an upright position. Angle, velocity, and acceleration (kinematic) were reconstructed for knee and ankle joints. The torques at these joints were calculated using inverse dynamics, taking into account anthropometric and inertial characteristics of each subject, including records from force data. Only activities of major muscles were recorded. The kinetic and EMG profiles were quantified during acceleration and deceleration phases of the upward squatting. Both healthy and PFPS subjects used the same kinetic and EMG strategies to perform the upward squatting, even though the magnitude of the muscle activities were decreased for the latter group. Compared to the control group, the PFPS subjects presented larger joint ankle torques and smaller knee joint torques. However, the subjects avoided keeping their knees very flexed at the initial position. Group differences in the kinetic and EMG strategies can be explained by differences in the initial position, suggesting a protective strategy used by subjects with PFPS. Therefore, for these subjects, coaches and therapists should avoid using this exercise when the knee is required to move above 40° flexion.
Assuntos
Teste de Esforço/métodos , Síndrome da Dor Patelofemoral/fisiopatologia , Postura , Amplitude de Movimento Articular/fisiologia , Adulto , Articulação do Tornozelo/fisiologia , Fenômenos Biomecânicos , Estudos de Casos e Controles , Eletromiografia/métodos , Feminino , Humanos , Articulação do Joelho/fisiologia , Masculino , Medição da Dor , Propriocepção/fisiologia , Valores de Referência , Adulto JovemRESUMO
Several shoulder dysfunctions are generally characterized as Shoulder Impingement Syndrome (SIS). Specifically, glenohumeral instability (GI) has been viewed as a primary cause of SIS in young individuals, mainly in overhead athletics. Past studies have associated GI with modifications in latency, recruitment order and/or EMG activity. However, it is not clear if pain and/or joint instability can account for these observed changes. The aim of this investigation was to analyze the effect of glenohumeral instability on the latencies and recruitment order of the superficial muscles of the glenohumeral and scapulothoracic joints in swimmers without pain symptom. Eight individuals with and eight without history of Shoulder Impingement Syndrome performed bilateral and simultaneous shoulder elevations at three different distances. The shoulder kinematics and EMG activities of glenohumeral and scapulothoracic muscles were registered. Results showed that subjects of both groups performed the task with similar latencies and recruitment order of the muscle activities. We conclude that shoulder instability does not necessarily affect the latencies and recruitment order of the shoulder muscles during the elevation of the shoulder in the scapular plane. Pain and other factors may be involved in the kinematics and electromyographic alterations demonstrated in other experiments.