Quote:
Originally Posted by Blitzzz
Moving a resistance through the air has always been the mainstay of exercise. The major difference between free and control movements is the free movement change in resistance through their arch with the relationship of the load and axis in the Line of gravity (LOG). This change affects muscle strength in varying portions of the Muscle excursion. Controlled movement maintains a "constant" resistance through the excursion of the Muscle.
Secondly with the high velocity of the free weight create inertia that elevates resistance at the ends of the Movement arch with direction change. This requires and additional reduction of start weights of about 10%.
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In each of the major barbell lifts (squat, press, bench press, and deadlift, AKA the slow lifts), the bar path is vertical, or as close to vertical as possible. Thus, there is no change in axis or line of gravity, no arch, and therefore no change in resistance. Where a leg press machine ontrols the path of resistance with lubricant and steel, a squat is controlled by the musculature of the legs, abdominals, and posterior chain, and all of the connective tissues and structures therein. A 400lb. squat is 400lbs. from the top, to the hole, and back to the top. The fact that there is a stretch refllex and "bounce" at the lowest point of the eccentric doesn't change the fact that the resistance is constant.
The Olympic lifts (snatch and clean & jerk, AKA the quick lifts), also have a vertical bar path. Some lifters perform the snatch with a slight forward arcing bar path, mainly to clear the kness before full extension. The "high velocity" is necessary to raise the weight to a point where it can be dropped under and caught while "floating" at the point where upward velocity(the pulls) is overcome by downward velocity (gravity). This is not a direction change that produces any additional resistance. If an athelete can front squat 300lbs., and deadlift 300lbs., he is physically strong enough to clean 300lbs. Conversely, an athlete with a 1000lb. leg press and a 200lb. seated row is not guaranteed to be able to clean even 150lbs., due to the lack of strengthened connective tissue, as well as the athlete's unfamiliarity with controlling heavy loads through his body's full range of motion, from deadlift start, through three pulls, to a catch in a rock-bottom front squat, and up into a postition for a jerk or press. People who come to Crossfit from a gym-rat, "bodybuilding" background where resistance is primarily controlled by pulleys, lubricant, and steel often run into serious injuries because of this.
The "reduction in start weights" is more a function of training and practicing form and technique on the technically demanding Olympic lifts, than any relation between the inherent inertia and the resistance of the lift itself.