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![]() By: Jamie Hale
This is a very popular exercise in commercial gyms and fitness mags. These sources propose this that movement is excellent for the abdominal region. In reality the abdominals play a stabilizing role in this movement as they prevent any significant movement in the pelvis. The prime mover in this exercise is actually the hip flexors. If your goal is to maximize stimulation of the abdominal muscles you must display a pike like movement as you attempt to crunch the abs to raise the legs vertically.
There are no clinical findings to support this statement. Force plate analysis indicates that heavy squats do not impose heavier loads on the body than those experienced with running and jumping (which can be 6 times bodyweight).
The idea that you can isolate a muscle with a particular movement is incorrect. When a limb is moved specific parts of the body have to be stabilized to allow that movement to occur. Some muscles begin a movement, others operate synergistically, others terminate movement, and other muscles become involved as fatigue sets in. All movement and stabilization are the result of coordinated muscle actions. We should lay the muscle isolation myth to rest and more accurately refer to certain movements as joint isolation. Also when doing bicep curls for example refer to the biceps as the prime mover not the muscle being worked.
This statement is very popular especially in gyms equipped with a multitude of machines. Research reveals that the act of erect, relaxed and unloaded sitting alone can increase stress on the lumbar spine by 40 percent. If an element of flexion occurs while sitting lumbar loading can almost double. It is of monumental importance to be aware of back positioning and have a sufficiently strong trunk when performing seated movements.
It is presumed this leads to more stress being imposed on the lumbar disks, thus promoting their degeneration. No research has yet been conducted to show any difference in spinal degeneration among belt users and non belt users. According to Siff, his research using EMG and muscle tension devices has shown that use of a belt can create circumstances for increasing rather than decreasing abdominal strength. External pressure exerted on the abs using a belt increases tension in them thus strengthening them assuming breath is held during the movement.
Recent research indicates that patellafemoral and soft tissue forces are greater during knee extensions than well-controlled squats. This is due to the fact the seated knee extensions prevent the hip joint from sharing the loading of the movement. In addition the controlled line of movement does not offer the natural patterns of linked joint movement, nor do they involve the central nervous system in producing natural daily patterns of motor control, thus knee extensions should play a minimal role in leg training. About Coach Hale Coach Hale is the owner of Total Body Fitness, Winchester Golden Gloves Boxing and MaxCondition Sports Conditioning. He designs comprehensive training programs for coaches and athletes worldwide. He is the author of Optimum Physique and contributor to numerous exercise and sports publications. Coach Hale is an official member of The World Martial Arts Hall of Fame in recognition of his strength and conditioning work with martial artists. He also serves as vice-chairman for the World Martial Arts Hall of Fame. To learn more about coach Hale visit his website.
Part 1: Myths and Truths.
References Siff, M, C (2000) Facts and Fallacies of Fitness. Siff. Thanks,
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