title: The effect of hip abduction on the EMG activity of vastus medialis obliquus, vastus lateralis longus and vastus lateralis obliquus in healthy subjects.
abstract: METHODS
  Controlled laboratory study.
  
  
  OBJECTIVE
  The purposes of this paper were to investigate (d) whether vastus medialis obliquus (VMO), vastus lateralis longus (VLL) and vastus lateralis obliquus (VLO) EMG activity can be influenced by hip abduction performed by healthy subjects.
  
  
  BACKGROUND
  Some clinicians contraindicate hip abduction for patellofemoral patients (with) based on the premise that hip abduction could facilitate the VLL muscle activation leading to a VLL and VMO imbalance
  
  
  METHODS
  Twenty-one clinically healthy subjects were involved in the study, 10 women and 11 men (aged X = 23.3 +/- 2.9). The EMG signals were collected using a computerized EMG VIKING II, with 8 channels and three pairs of surface electrodes. EMG activity was obtained from MVIC knee extension at 90 degrees of flexion in a seated position and MVIC hip abduction at 0 degrees and 30 degrees with patients in side-lying position with the knee in full extension. The data were normalized in the MVIC knee extension at 50 degrees of flexion in a seated position, and were submitted to ANOVA test with subsequent application of the Bonferroni multiple comparisons analysis test. The level of significance was defined as p < or = 0.05.
  
  
  RESULTS
  The VLO muscle demonstrated a similar pattern to the VMO muscle showing higher EMG activity in MVIC knee extension at 90 degrees of flexion compared with MVIC hip abduction at 0 degrees and 30 degrees of abduction for male (p < 0.0007) and MVIC hip abduction at 0 degrees of abduction for female subjects (p < 0.02196). There were no statistically significant differences in the VLL EMG activity among the three sets of exercises tested.
  
  
  CONCLUSIONS
  The results showed that no selective EMG activation was observed when comparison was made between the VMO, VLL and VLO muscles while performing MVIC hip abduction at 0 degrees and 30 degrees of abduction and MVIC knee extension at 90 degrees of flexion in both male and female subjects. Our findings demonstrate that hip abduction do not facilitated VLL and VLO activity in relation to the VMO, however, this study included only healthy subjects performing maximum voluntary isometric contraction contractions, therefore much remains to be discovered by future research.
authors.affiliation: Department of Biomechanics, Medicine and Rehabilitation of Locomotor Apparatus, Ribeirão Preto School of Medicine, University of São Paulo (FMRP-USP), Ribeirão Preto, SP, Brazil. deborabg@fmrp.usp.br
authors.forename: Débora
authors.initials: D
authors.lastname: Bevilaqua-Grossi
authors.forename: Vanessa
authors.initials: V
authors.lastname: Monteiro-Pedro
authors.forename: Rodrigo Antunes
authors.initials: RA
authors.lastname: de Vasconcelos
authors.forename: Juliano Coelho
authors.initials: JC
authors.lastname: Arakaki
authors.forename: Fausto
authors.initials: F
authors.lastname: Bérzin