Read Online Starting Strength by Mark Rippetoe - Free Book Online Page A
Authors: Mark Rippetoe
Tags: strength training
Ads: Link
greater the weight and distance, the larger the effect, the system behaves like a moment arm acting on a point of rotation at the mid-foot. This leverage has the potential to add quite a bit to the force needed to overcome the weight of the bar, which happens as the bar moves forward of the balance point.
Forward is the usual direction of off-balance movement due to the vagaries of human anatomy – the ankle is behind the mid-foot, the knees articulate forward, and the eyes are forward-directed. Most people who have been training for more than a couple of weeks will not put themselves in the rather awkward position of moving back with the bar on the shoulders. And since the body is in an asymmetrical position at the bottom of a squat or a deadlift, with more of the body behind the bar than in front of it, it would be simplistic to conclude that the same amount of movement forward and backward from the mid-foot would affect the system symmetrically, i.e., that a forward bar movement of 3 inches would have to be reacted against with the same force as a backward bar path deviation of the same 3 inches.
Considered in this context, the term “out of balance” means that a moment (rotational force) exists between the bar and the mid-foot vertically along the body, and this moment must be controlled with an amount of force necessary to cancel its effects. This is force that could be more productively used to lift more weight on the bar if it were “in balance.” So your ability to control the moment between bar and mid-foot – your ability to maintain a vertical relationship between barbell and mid-foot – is your ability to use good technique in lifting.
Figure 2-30. “Balance” defined as the absence of a horizontal moment arm along a vertically-oriented system.
We must consider the effects of two systems of leverage while we squat. The moments operating horizontally along the segments of the body are produced by the force of gravity acting on the load. They are inherent in squatting down and standing back up under a heavy barbell; they make up the resistance against which we work to get strong. The moment operating vertically between the bar and the mid-foot balance point, however, must be kept at ZERO to avoid wasting force that could otherwise be used to lift more weight. Both of these moments must be considered when you’re analyzing the biomechanics of the system.
Figure 2-31. Good technique in the squat is the ability to maintain zero moment between the bar and the mid-foot balance point. This completes the concept presented in Figure 2-7 – the extra effort is due to the existence of the moment arm between bar and midfoot. ( M.A. = moment arm )
Figure 2-32. The concepts of moment force applied to the body during the squat. (A) The moment force A, along the segments, is inherent in performing the motion of squatting and is thus the force against which we exercise. (B) The moment force B, between the bar and the mid-foot balance point considered vertically, must be kept to ZERO for greatest efficiency. Moment force B adversely affects the work done against moment force A. ( M.A. = moment arm )
Common Problems Everyone Should Know How to Solve
A correct squat will always have certain identifiable characteristics controlled by skeletal anatomy and muscle function. For any squat, back or front, these conditions will be satisfied, making it relatively easy to determine whether form and position are correct. At the top, all the skeletal components that support the bar – the knees, hips, and spine – will be locked in extension so that the muscular components have to exert only enough force to maintain this position, in which compression is the primary force on the skeletal components. The job of the muscles here is to keep the bones lined up correctly so they can hold up the load. The bar will be over the middle of the foot. The heavier the weight, the more critical this position will be.
When
Forward is the usual direction of off-balance movement due to the vagaries of human anatomy – the ankle is behind the mid-foot, the knees articulate forward, and the eyes are forward-directed. Most people who have been training for more than a couple of weeks will not put themselves in the rather awkward position of moving back with the bar on the shoulders. And since the body is in an asymmetrical position at the bottom of a squat or a deadlift, with more of the body behind the bar than in front of it, it would be simplistic to conclude that the same amount of movement forward and backward from the mid-foot would affect the system symmetrically, i.e., that a forward bar movement of 3 inches would have to be reacted against with the same force as a backward bar path deviation of the same 3 inches.
Considered in this context, the term “out of balance” means that a moment (rotational force) exists between the bar and the mid-foot vertically along the body, and this moment must be controlled with an amount of force necessary to cancel its effects. This is force that could be more productively used to lift more weight on the bar if it were “in balance.” So your ability to control the moment between bar and mid-foot – your ability to maintain a vertical relationship between barbell and mid-foot – is your ability to use good technique in lifting.
Figure 2-30. “Balance” defined as the absence of a horizontal moment arm along a vertically-oriented system.
We must consider the effects of two systems of leverage while we squat. The moments operating horizontally along the segments of the body are produced by the force of gravity acting on the load. They are inherent in squatting down and standing back up under a heavy barbell; they make up the resistance against which we work to get strong. The moment operating vertically between the bar and the mid-foot balance point, however, must be kept at ZERO to avoid wasting force that could otherwise be used to lift more weight. Both of these moments must be considered when you’re analyzing the biomechanics of the system.
Figure 2-31. Good technique in the squat is the ability to maintain zero moment between the bar and the mid-foot balance point. This completes the concept presented in Figure 2-7 – the extra effort is due to the existence of the moment arm between bar and midfoot. ( M.A. = moment arm )
Figure 2-32. The concepts of moment force applied to the body during the squat. (A) The moment force A, along the segments, is inherent in performing the motion of squatting and is thus the force against which we exercise. (B) The moment force B, between the bar and the mid-foot balance point considered vertically, must be kept to ZERO for greatest efficiency. Moment force B adversely affects the work done against moment force A. ( M.A. = moment arm )
Common Problems Everyone Should Know How to Solve
A correct squat will always have certain identifiable characteristics controlled by skeletal anatomy and muscle function. For any squat, back or front, these conditions will be satisfied, making it relatively easy to determine whether form and position are correct. At the top, all the skeletal components that support the bar – the knees, hips, and spine – will be locked in extension so that the muscular components have to exert only enough force to maintain this position, in which compression is the primary force on the skeletal components. The job of the muscles here is to keep the bones lined up correctly so they can hold up the load. The bar will be over the middle of the foot. The heavier the weight, the more critical this position will be.
When
Similar Books
