Delayed onset of electromyographic activity of vastus medialis obliquus relative to vastus lateralis in subjects with patellofemoral pain syndrome

Comparison of different analysis techniques for the determination of muscle onset in individuals with patellofemoral pain syndrome

“…In this study, the onset detection was also performed using the automatic technique but was measured in relation to the peak without considering the standard-deviations. And in the literature, there are studies that confirm the results showed using the cross-correlation technique too, such as those presented by Powers et al (1996), Brindle et al (2003) and Cavazzuti et al (2010), which were also designed to quantitate the delay between the activation of the VMO and VL muscles to differentiate individuals with PFPS from clinically healthy subjects during the ascent of stairs. These studies concluded that, using only the onset, it is not possible to make this distinction.…”

“…The observed errors that were associated with visual inspection and cross correlation were not as high, 3.77 ms and 10.19 ms, for the control and PFPS groups using visual inspection, respectively, and 2.56 ms and 3.27 ms, for the control and PFPS groups using cross-correlation, respectively. It is noted that despite the variation among these techniques, all of the techniques demonstrated that the variability was higher in the PFPS group, indicating that the multifactorial etiology of the syndrome can also affect the results (Cavazzuti et al, 2010). In this study, besides the medical diagnoses, an assessment protocol was applied as proposed by Cowan et al (2002), Jensen et al (2007) and Magee (2008) and Table 2 Values of the mean, SD and SEM of the onset using the three techniques and their associated statistical significances.…”

Influência de diferentes tipos de calçado na atividade eletromiográfica do músculo quadríceps de mulheres ao subir e descer degrau

“…Em relação ao tempo de ativação, Cavazzuti et al (19) não identificaram diferença na comparação entre VMO e VL em indivíduos sintomáticos e assintomáticos durante tarefa em cadeia cinética fechada com apoio bipodal, rejeitando assim a hipótese de que os indivíduos portadores da SDFP apresentavam um retardo no tempo de ativação do VMO quando comparados a indivíduos normais. Da mesma forma, os resultados do presente estudo mostram que durante a realização de tarefas com apoio unipodal não há essa diferença, independentemente do tipo de calçado, rejeitando também essa hipótese.…”

“…No entanto, alguns autores (19,20) relataram não ter encontrado alterações na atividade e no tempo de ativação dos músculos estabilizadores em indivíduos com SDFP, sugerindo que o desequilíbrio entre VMO e VL não seria um fator determinante. Por fim, Dye (21) sugere que o desequilíbrio dos estabilizadores estáticos e dinâmicos, quando presente de forma isolada, não predispõe o desenvolvimento da SDFP, mas sim a associação de diversos fatores.…”

Delayed onset of vastii muscle activity in response to rapid postural perturbations following eccentric exercise: a mechanism that underpins knee pain after eccentric exercise?

“…The onset of vastus medialis obliqus (VMO) activity typically occurs earlier than that of the vastus lateralis (VL) or at least synchronously during the postural perturbations,3 stair-stepping4 and patella tendon reflex reactions 2 5 6. Consequently, delayed onset of the VMO compared with VL activity has frequently been reported as a potential cause for patellar maltracking and development of pain 7…”