نوع مقاله : مقاله پژوهشی
1 دکترای بیومکانیک ورزشی، استادیار دانشکده تربیت بدنی و علوم ورزشی، دانشگاه گیلان، رشت، ایران
2 دکترای حرکات اصلاحی، استادیار دانشکده تربیت بدنی و علوم ورزشی، دانشگاه بوعلی سینا، همدان، ایران
3 دانشجوی دکتری حرکات اصلاحی، دانشکده تربیت بدنی و علوم ورزشی، دانشگاه خوارزمی، کرج، ایران
4 کارشناس ارشد تربیت بدنی، دانشکده تربیت بدنی و علوم ورزشی، دانشگاه بوعلی سینا، همدان، ایران
عنوان مقاله [English]
Background and Aim: Selection of contraction type to achieve muscle strength and fitness is very important, especially when the main goal is improvement of certain parts of quadriceps. Thus, the purpose of the current study was to compare the quadriceps muscles activity among three types of knee extensor contractions with different loads in young females.
Materials and Methods: A total of 20 healthy females with the mean age of 24.7±4.5 years, heaight 168.3±9.4 cm, and weight 62.6±7.2 kg, volunteered to participate in the study and performed isometric, concentric, and eccentric contractions with loads weighing 30-80% 1RM weight using isokinetic dynamometer. Measurement of vastus medialis, vastus lateralis, and rectus femoris activity was carried out using 8-channels electromyography. Data analysis was performed running repeated measures analysis of variance and bonferroni tests.
Results: There was no difference observed between dominant and non-dominant lower limb in muscle activity (p>0.05). Quadriceps activity in eccentric contraction was less than concentric and isometric contractions (P=0.000), and vastus medialis and vastus lateralis activities were more than that of rectus femoris (P=0.002). In the lighter loads, vastus lateralis was more active than the other two muscles (P<0.01), but in the higher loads, no significant difference was observed. In lighter loads, quadriceps activity in eccentric contraction was less than those of the other two contractions (P<0.01), but in higher loads, no significant difference was noticed.
Conclusion: The results of the current study suggest that quadriceps group has the most activity during concentric contraction. The more interesting result is that by changing the contraction type from eccentric to concentric, recruitment of vastus medialis increases. These results are very important for chronic pathological conditions of the patellofemoral joint since these disorders are often attributed to the weakness of quadriceps, especially its medial part.