Effect of the contraction of medial rotators of the tibia on the electromyographic activity of vastus medialis and vastus lateralis
Received 16 August 2007; received in revised form 29 January 2010; accepted 29 January 2010. published online 02 March 2010. Corrected Proof
Abstract
Purpose
This study attempted to assess if the resisted contraction of medial rotators of the tibia increases the ratio between the activity of vastus medialis (VM) and vastus lateralis (VL) during maximal isometric contractions (MIC) of the quadriceps femoral (QF) muscle at 90° of knee flexion.
Methods
About 24 female subjects participated in this study, performing four series MIC of the QF. In the first series subjects performed only MIC of the QF muscle, whereas in the other three there was MIC of the QF with resisted contraction of medial rotators of the tibia, with the tibia positioned in medial, neutral and lateral rotation. During each contraction, VM and VL electromyographic signal (EMGs) and QF force were collected, being the EMGs root mean square (RMS) used to access the activity level of these muscles.
Results
The use of the General Linear Model (GLM) test showed that for α=0.05 there was a significant increase in the VM:VL ratio when the resisted contraction of medial rotators of the tibia was performed with the tibia in medial (p=<0.0001), neutral (p=<0.0001) and lateral rotation (p=0.001). The same test showed that during MIC of the QF associated to resisted contraction of medial rotators of the tibia there were no significant differences in the VM:VL ratio between the three tibial rotation positions adopted (p=0.866 [medial–neutral]; p=0.106 [medial–lateral]; p=0.068 [neutral–lateral]).
Conclusions
The resisted contraction of medial rotators of the tibia increases the VM:VL ratio during MIC of the QF and the tibial rotation position does not influence the VM:VL ratio during MIC associated to resisted contraction of medial rotators of the tibia.
Department of Physiotherapy, Escola Superior de Tecnologia de Saúde do Instituto Politécnico do Porto, Rua Valente Perfeito, 322, 4400-330 Vila Nova de Gaia, Portugal
ABSTRACT
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