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Tip 113: Healthy Knees - Focus on Quadriceps Strength and Total Muscle Activation

Wednesday, June 22, 2011 10:03 AM
Knee dysfunction is often due to a weakness of one or more of the quadriceps muscles, which include the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. New research shows that the common problem of neuromuscular impairment of the quad muscles substantially affects strength of the quad, meaning that one or more of the quad muscles isn’t firing effectively. The critical importance of muscle activation for strength training and sports is supported with evidence from individuals recovering from knee surgery. Researchers found that weakness of the quadriceps is due more to the failure of voluntary muscle activation than to muscle atrophy after surgery.

Aside from providing strategies to support optimal recovery following knee surgery, this study indicates the importance of activating the muscles prior to exercise. Training with exercises that recruit the maximal number of motor units is necessary as well. A major component of muscle activation is priming the neuromuscular system to fire when lifting weights or playing sports. Plus, in daily life if muscles don’t activate properly, it can lead to bad posture, pain, and repeated stress on muscles, with an ultimate decrease in strength or atrophy. To activate muscles prior to training, use a warm up specific to the exercises you’ll be performing: for example, if you plan to squat, do so using bodyweight or a very light load. Foam rolling to improve neural activation can also be done prior to a specific warm up.

To activate and train the quadriceps, one strategy is to isolate the muscle through single leg squats. Initially, these can be done onto a bench, with progressions being a single leg squat without a bench, or a rear foot-elevated single leg squat with weight on the back or front. Regular squats and Olympic lifts are ideal exercise for maximal motor unit recruitment once a base level of strength has been established.

To read more about muscle activation, check out Selecting the Best “Bang for your Buck” Exercises.

Petterson, S., Barrance, P., Marmon, A., Handling, T., Buchanan, T., Snyder-Mackler, L. Time Course of Quad Strength, Area, and Activation after Knee Arthroplasty and Strength Training. Medicine and Science in Sports and Exercise. 2011. 43(2), 225-232.

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