مقاله Investigating the Role of Foot Placement on the Muscular Forces of Knee Extensors in Horizontal Leg Press: A Static Optimization Approach با word دارای 6 صفحه می باشد و دارای تنظیمات در microsoft word می باشد و آماده پرینت یا چاپ است
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بخشی از متن مقاله Investigating the Role of Foot Placement on the Muscular Forces of Knee Extensors in Horizontal Leg Press: A Static Optimization Approach با word :
سال انتشار: 1392
محل انتشار: بیستمین کنفرانس مهندسی زیست پزشکی ایران
تعداد صفحات: 6
چکیده:
Horizontal leg press is a basic weight training exercise to strengthen extensor muscles of knee joint. Considering the specific purpose of this training, it’s performed with differenttechniques. One of the major debates about performing this task concerns foot placement on the foot-plate. In this study, in orderto investigate the effect of foot placement on the muscle contraction of knee extensors, a 3-DOF musculoskeletal model oflower-extremity was developed. This model was comprised of 40skeletal muscles of lower-extremity. Each muscle was modeled with a phenomenological Hill-based model in accompanied with a rigid tendon. Considering the position of feet on the foot-plate (high or low), two types of experiments were designed: Leg Press High (LPH) and Leg Press Low (LPL). 6 healthy volunteers (2 women and 4 men) participated in this study. Experiments wereperformed at 30% and 70% of each person’s MVC (the maximum weight in which a person could perform the exercisecorrectly) on the LPL and LPH protocols. Amalgamating themean values of kinematic data and a constrained static optimization (sum of squared activations as the objective functionand discritisized state equations of the multibody system as constraints), the required activation level of each muscle wasobtained. The results showed a significant difference between the obtained muscle forces for knee extensors (vastus intermedius,vastus lateralis, vastus medialis, and rectus femoris) in eachtechnique (p<0.05). The muscle forces obtained in LPH technique were significantly smaller from the same ones in LPL. Thisobservation suggests that if strengthening the knee extensors is of desire, LPH technique is not the correct format for performingthe exercise. Another important spotlight in the results concerned the activation patterns of knee extensors. Despite thesynergic behavior of all the extensors, because of the different operating range of these muscles, dissimilarity between activation patterns was observed.
