The prevailing recommendation from orthopedists, physical therapists, and exercise professionals concerning the strengthening of the muscles that surround the knee is this: “Closed chain” exercises (these include squats, leg presses, lunges, step-ups) are preferable to “open chain” exercises (these include leg extensions and leg curls) for individuals with knee pain or individuals who have undergone knee surgeries. Some practitioners have gone so far to suggest that open chain movements such as leg extensions should be avoided completely as they may contribute to knee pain. Investigators of a research study sought to answer the question: For patients with prolonged knee pain (patellofemoral pain), which form of exercise is more effective? A team of researchers from Ghent University in Belgium hypothesized that the long-term benefits of closed chain movements would be more pronounced than opened chain movements. Researchers separated individuals who had experienced long-term knee pain into two different groups: closed chain and open chain. After a 5-year follow up, researchers were surprised by the results; patients performing open-chain exercise faired either equally as well or better than the closed chain group. The researchers concluded that the prejudice toward closed chain movements is unfounded and recommend the inclusion of open chain exercises in order improve long-term pain reduction and enhanced functionality.
I recently had a client tell me that her physical therapist told her that she should probably avoid leg extension and leg curl as these exercises trained “muscles” but that they were not “functional.” This client is very well informed, so she knew exactly how off-base this advice was. The logical response to this physical therapist (and to all of those who espouse so-called “functional training”) is this: What causes function? The answer of course is MUSCLE and MUSCLE CONTRACTION. Here is the bottom line. The goal of strength training should be to improve the ability of a muscle to contact and produce force. Then and only then can functional ability (our ability to bend, run, swing, ski, jump, climb, live) actually improve.
Side note: To be precise, we can see improvements in performance by practicing a specific “closed-skill.” This simply means that if we practice a specific task or skill, we will get better at it. The limitation to this is that this improved performance does NOT transfer to other tasks or skills. This is a basic and long held tenet in the field of motor learning and control. Exercise should be all about changing our physiology, NOT about improving our skills.
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