The Effect of altering knee position and squat depth on VMO: VL EMG ratio during squat exercises

Shapour Jaberzadeh, Daniel Yeo, Maryam Zoghi

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3 Citations (Scopus)


Background: Patellofemoral pain syndrome is an extremely common condition, believed to be caused by altered activation of vastus medialis obliquus (VMO), leading to maltracking of the patella. Aim: This study aimed to investigate the effect of altering knee movement and squat depth on the ratio of VMO and vastus lateralis (VMO:VL) during squat exercises. Method: Eighteen (7 male and 11 female) healthy, asymptomatic participants performed semi-squat exercises with three squat depths (20º, 50º and 80º of knee flexion) while following three knee movement paths (neutral, varus or valgus). Normalized VMO:VL ratio from linear envelope surface electromyography was analysed.Results: No significant effect was found for gender (p = 0.87), leg dominance (p = 0.99) or knee position (p = 0.44). A significant effect was found for squat depth (p < 0.001) with both the 50° and 80° squats showing increases in VMO : VL ratio (p = 0.031 and p = 0.028), respectively. The VMO : VL ratio was not influenced by gender, leg dominance or knee position in semi-squat exercises.Discussion and Conclusion: Increases in relative VMO activation did occur in ‘deeper’ squat depths (50° and 80° knee flexion) compared with the 20° condition. Further research is needed in this area concerning the effects of such exercise modifications on a symptomatic patellofemoral pain syndrome population.
Original languageEnglish
Pages (from-to)164-173
Number of pages10
JournalPhysiotherapy Research International
Issue number3
Publication statusPublished - 2016


  • patellofemoral joint
  • squat exercises
  • vastus medialis obliquus
  • vastus lateralis

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