Objective: Patellofemoral pain syndrome (PFPS) is one of the most common knee chronic disorders especially among females that is closely related to forces imbalance of vastus medial is oblique (VMO) and vastus lateral is (VL) muscles. The purpose of study was to examine the effect of knee isokinetic extension in maximum lateral tibia rotation on VMO and VL amplitudes in PFPS patients.

Materials & Methods:  Thirty-six women with PFPS participated voluntarily in this study and were randomly placed in one of three groups included the VMO selective isokinetic strengthening exercise, quadriceps general strengthening and control groups. Each exercise was performed for 8 weeks. Muscle RMS of VMO and VL and VMO/VL RMS ratio were recorded and calculated before and after training using of an 8-channels electromyography system. Data analysis was made by analyses of variance with repeated measures.

Results: In baseline, VMO amplitude was less than VL in all groups (P≤0.05), but after interventions, it was more than VL in selective group (P=0.01) and less than VL in general (P=0.001) and control (P=0.036) groups. Before interventions, there was no difference between groups in muscles amplitude (P>0.05). Yet, after interventions, VMO amplitude and VMO/VL amplitude ratio were more in selective group than in general and control groups (P≤0.001), and VL amplitude was more in general group than in selective and control groups (P≤0.01).

Conclusion: According to the study results, isokinetic extension training with maximum lateral tibia rotation and in close to knee full extension can be recommended as an appropriate training for improving VMO/VL electrical activity ratio and decreasing imbalance between lateral and medial vastus muscles amplitudes in patients with PFPS.

Objective: In recent years, it has been focused much attention on gait analysis. Factors such as speed, age and gender affect gait parameters. The purpose of the present study was to compare the electromyographic activity pattern of knee two-joint muscles between younger and older subjects in different gait speeds.

Matterials & Methods: The method of current study was analytical cross-sectional method in which 15 healthy young men and 15 old men, were selected conveniently. Electromyographic activity of rectus femoris, biceps femoris, semitendinus and gastrocenemius were recorded during walking with preferred (100%), slow (80%) and fast (120%) speeds in a 10 meter walkway. Normalized RMSs of muscles were compared using RM-ANOVA and Tokey’s tests by SPSS 18 software.

Results: According to results, RMSs of rectus femoris in midstance (P<0.01) and gastrocenemius in loading response (P=0.02) phases in all walking speeds were higher in older subjects than in younger ones, and it increased with speed in both age groups (P<0.01). Biceps femoris RMS in terminal stance at 80% speed, was lower in older subjects than in younger ones (P=0.01) and it increased with walking speed (P=0.01). Semitendinus activity in loading and midstance phases at 120% speed was higher in older subjects than in younger ones (P<0.01), and it increased with speed in both age groups in swing phase (P<0.05).

Conclusion: According to the results, older subjects have more muscle co-contraction around knee at high speed in midstance phase than younger subjects. These age-related changes in muscle activity, leads to increase in joint stiffness and stability during single support, and probably play a role in reducing push off power at faster speeds.