The leg extension machine was designed to isolate the quadriceps muscles, which are the muscles in the front of the thigh. It is available in most gyms and fitness centers. The safety and efficiency of the leg extension machine is one of the most controversial subjects in the fitness industry. The machine definitely strengthens the quadriceps muscles, but the risks may outweigh the rewards.

Muscular Imbalance

Most people are already stronger in their quadriceps than their hamstrings. This muscular imbalance can lead to serious knee injuries. The quadriceps straighten your legs, whereas the hamstrings bend them. In athletic movements such as jumping, your knees must bend upon landing. This protects them from injury. Landing with straight legs can cause the joints to hyperextend, which can cause injury. Since the leg extension is a quadriceps isolation exercise, it can exacerbate this imbalance.






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Lack of Muscle Symmetry

Muscular imbalance refers to the function of the muscles. Symmetry refers to the body's overall appearance. Overly developed quadriceps, paired with less-developed hamstrings, destroys muscular symmetry. A big bulge in the front of the legs with flabby muscles in the back is unattractive. While the leg extension machine is usually easy to use, many hamstring machines put the user at a biomechanical disadvantage. The adjustments, for example, are often geared for taller people. This causes shorter people to use much less weight than they use on the leg extension, resulting in an imbalance that contributes to the lack of muscular symmetry.

Shearing Forces on the Knee

The leg extension is an open chain exercise, which means that the foot is in a free, as opposed to a fixed, position. This type of exercise can place shearing forces on the knee, which can make them susceptible to injury. A study on this subject was published in the April 1998 edition of "Medicine & Science in Sports & Exercise."
The study, titled "Biomechanics of the Knee During Closed Kinetic Chain and Open Kinetic Chain Exercises," compared the biomechanical forces of the leg extension machine with those of closed chain exercises such as the squat and the leg press. The researchers found that tension in the anterior cruciate ligament, which is in the knee, occurred during the full extension phase of the leg extension.

Patellar Subluxation

Patellar subluxation is the medical term for knee dislocation. An article published in the November 2003 edition of the "Journal of Orthopedic Sports Physical Therapy" compared the potential for subluxation during the leg extension and the squat. The study, titled "Patellofemoral Kinematics During Weight-Bearing and Non-Weight-Bearing Knee Extension in Persons With Lateral Subluxation of the Patella" was performed at the Musculoskeletal Biomechanics Research Laboratory, Department of Biokinesiology and Physical Therapy at the University of Southern California. The researchers found that subluxation was greater during the leg extension exercise.


Read more: http://www.livestrong.com/article/52816 ... z1jFshmgzW

ROHIID@hotmail.com skrev:Så det lige meget om man laver, det eller ej ?

ROHIID@hotmail.com skrev:Hvilke andre alternativer kunne det være?

Jeg laver lige i øjeblikket, Front squat for mine quadriceps er det nok eller burde jeg lave flere øvelser ??