Ever notice that your gym owner changes the padding on the leg extentions about as frequently as Paris Hilton changes her clothes? That is because the leg extention in arguably the most often-used piece of leg equipment in to gym. Everyone fromserious bodybuilders to athletes to soccer moms and midle aged buisnessmen will have a turn at this machine.
Of course, unline the CC exercises, the leg extention does not demand the same amount of energy expediture. Because it is an open chain movement taht is, it is not amultijoint exercise and the foot is not grounded but free--fewer stabilizers and antagonists are called into action, presenting fewer energy demands. In addition, there is no contraction between fron and back thighs, But the leg extention hits two sizable and important muscle sections that add depth,density, and fullness to the fron thigh: the long head runnign form the hip to the knee, the reuctus frmoris; and the vastus intermedius, running beneath it.
As a rule, to generate greater strength during a movement, pestrech the working muscle. That is why many leg curl machines are angled which adds extra stretch to the hamstring, allowing the muscle to contract more strongly. But that is not the case with the leg extention, though you often see trainers angling the seat rearward in an effort to add prestrech and hence perceived strength of repping.
One French study, however, found that this approach actually limits contractile strength. An EMG analysis revealed that a ninety- degree angle between the thigs and torso helped lifter the greates number of muscle fibers. In face, it resulted in as much as a 42% greater mescle position, it stands to reason you compromise biomechanical advantages of the exercises--the increased angle allows for greater cheating during the exercise, leading to sperveption of greater strength. Cheatinghas its place in training, of course especially doing so with the leg extentions since the exercise involves shear and not compressive forces, which can result in improper tracking of the tibia which placing the anterior cruciate legamentat greater risk of injury.
