بررسي تاثير دو زاويه 20 و 60 درجه فلكشن مفصل زانو در زنجيره حركتي بسته بر روي نسبت فعاليت الكتروميوگرافي عضله پهن مايل داخلي به عضله پهن خارجي حين دو تمرين چمباتمه و پايين آمدن از پله

The Effect of 20 and 60 Degrees of Knee Flexion on Electromyography Biofeedback and Ratio of Vastus Medials Oblique to Vastus Lateralis Muscles in Closed Kinetic Chain During Squat and Step-Down Exercises

This study was performed on 36 healthy men volunteers and nonathletes aged 20 to 30 years. The main aim of this study was to determine the effects of 20 and 60 degrees of knee flexion on electromyography of VMO and VL muscles during squat and step-down exercises. In this study, considering the dominant lower exteremity, surface electrodes were attached on VMO and VL muscles. An electronic goniometer, equipped with visual - auditory feedback and warning system was placed on the lateral region of the subjectʹs knee. In order to make a position of 20 or 60 degrees of knee flexion during two tasks, electrical activities of VMO and VL muscles were recorded by an electromyographic biofeedback, and the areas under the two curves were used for statisical analysis. Statistical analysis with paired t-test showed that VMO and VL activity in 60 degrees of knee flexion during squat and step-down was increased in comparison with 20 degrees of knee flexion (P=0.0001). On the other hand, VMO activity was significantly increased in all positions except 20 degrees of knee flexion during squat in comparison with VL activity. In addition, the results of comparing VMO/VL electrical activity ratios in 20 and 60 degrees of knee flexion during the two different tasks showed that this ratio was significantly increased only in 60 degrees comparing with 20 degrees of knee flexion during squat exercises, (p = 0.001). In other conditions, the comparison of ratios showed no significant differences (p>0.05). Considering the significant increase of VMO activity in comparison with VL in 20 degrees of knee flexion during step-down exercise comparing with squat exercise with counterpart degrees of knee flexion, it seems that the strengthening of VMO muscle in the initial degrees of knee flexion during step-down exercise, has great value. Although, comparing the ratios of activity of the muscles in 60 degrees of knee flexion during two tasks the increment of VMO/VL ratio in 60 degrees in squat exercise was not significant (p=0.062), 60 degrees of knee flexion may be import in VMO strengthening.