Objetivo: A proposta desse trabalho foi investigar o efeito da rotação do quadril na atividade elétrica dos músculos Vasto Medial Oblíquo (VMO), Vasto Lateral Oblíquo (VLO) e Vasto Lateral Longo (VLL) no agachamento a 45º de flexão do joelho associado à posição neutra, rotação lateral a 45º e rotação medial a 15 e 30º de quadril. Materiais e Método: Foram avaliadas 27 mulheres, sendo 15 mulheres normais do grupo Controle (21,1±2,1 anos) e 12 portadoras de Síndrome da Dor Femoropatelar (SDFP) (21,0±2,3 anos). A atividade elétrica do músculo quadríceps foi captada por eletrodos ativos diferenciais simples de superfície, eletromiógrafo de 8 canais e programa Aqdados 7.2.6. Os dados foram normalizados pela porcentagem da média do agachamento a 75º com o quadril em posição neutra RMS (µV). A análise estatística utilizada foi a ANOVA two way com medidas repetidas e Turkey post hoc (p<0,05). Resultados: Os resultados evidenciaram interação entre grupos e músculos (p=0,00), independente da posição do quadril (p=0,39) e não houve interação entre grupos e posições do quadril (p=0,96). Os músculos VMO e VLL do grupo SDFP apresentaram atividade elétrica significativamente maior que o VMO (p=0,00) e VLL (p=0,04) do grupo controle. Por outro lado, a atividade elétrica do músculo VLO não apresentou diferença significativa entre os grupos (p=0,99). Conclusão: Os resultados dessa pesquisa, nas condições experimentais utilizadas, sugerem que a rotação do quadril não influenciou a atividade elétrica das porções do quadríceps nos dois grupos no agachamento a 45º de flexão do joelho.

Objective: The purpose of this study was to evaluate the effect of hip rotation on the electrical activity of the Vastus Medialis Obliquus (VMO), Vastus Lateralis Obliquus (VLO) and Vastus Lateralis Longus (VLL) muscles when squatting with 45º knee flexion, in association with the neutral position, 45º lateral rotation and 15 and 30º medial hip rotation. Method: 27 women were evaluated: 15 healthy women as a control group (21.1 ± 2.1 years) and 12 subjects with patellofemoral pain syndrome (PFPS) (21.0 ± 2.3 years). The electrical activity of the quadriceps muscle was detected using simple active differential surface electrodes, an eight-channel electromyography system and the Aqdados 7.2.6 software. The data were normalized by the mean squatting percentage at 75º with the hip in the neutral position RMS (µV). Two-way ANOVA with repeated measurements followed by the Tukey post hoc test (p<0.05) was used for statistical analysis. Results: The results revealed interaction between groups and muscles (p=0.00), independent of hip position (p=0.39), and there was no interaction between groups and hip positions (p=0.96). The VMO and VLL muscles of the PFPS group showed significantly greater electrical activity than did VMO (p=0.00) and VLL (p=0.04) muscles from the control group. On the other hand, the electrical activity of the VLO muscle did not present any significant difference between the groups (p=0.99). Conclusion: Under the experimental conditions utilized, the results suggested that hip rotation did not alter the electrical activity of the quadriceps portions in either group when squatting with 45º knee flexion.

The present study evaluated functional changes of quadriceps muscle after injury induced by eccentric exercise. Maximal isometric torque of quadriceps and the surface electromyography (root mean square, RMS, and median frequency, MDF) of the vastus medialis oblique (VMO) and vastus lateralis (VL) muscles were examined before, immediately after and during the first 7 days after injury. Serum creatine kinase (CK) levels and magnetic resonance imaging (MRI) were used to identify muscle injury. The subject was used as her own control and percent refers to pre-injury data. Experiments were carried out with a sedentary 23-year-old female. Injury was induced by 4 bouts of 15 maximal isokinetic eccentric contractions (angular velocity of 5º/s; range of motion from 40º to 110º of knee flexion). The isometric torque of the quadriceps (knee at 90º flexion) decreased 52% immediately after eccentric exercise and recovered on the 5th day. The highest reduction of RMS occurred on the 2nd day after injury in both VL (63%) and VMO (66%) and only VL recovered to the pre-injury level on the 7th day. Immediately after injury, the MDF decreased by 5 and 3% (VMO and VL, respectively) and recovered one day later. Serum CK levels increased by 109% on the 2nd day and were still increased by 32% on the 7th day. MRI showed large areas of injury especially in the deep region of quadriceps. In conclusion, eccentric exercise decreased the isometric torque and electromyographic signals of quadriceps muscle, which were recovered in one week, despite the muscle regeneration signals.