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Spring-like behavior of the musculos...

Shigeoka, Cassie Akiko.

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Spring-like behavior of the musculoskeletal system: From whole body to muscle fiber mechanics.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Spring-like behavior of the musculoskeletal system: From whole body to muscle fiber mechanics./
Author:	Shigeoka, Cassie Akiko.
Description:	119 p.
Notes:	Source: Dissertation Abstracts International, Volume: 65-02, Section: B, page: 0513.
Contained By:	Dissertation Abstracts International65-02B.
Subject:	Biology, Animal Physiology. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3121694
ISBN:	0496690450

Spring-like behavior of the musculoskeletal system: From whole body to muscle fiber mechanics.
Shigeoka, Cassie Akiko.

Spring-like behavior of the musculoskeletal system: From whole body to muscle fiber mechanics. - 119 p.

Source: Dissertation Abstracts International, Volume: 65-02, Section: B, page: 0513.

Thesis (Ph.D.)--University of California, Berkeley, 2003.

The musculoskeletal system displays spring-like behavior from the whole body level to that of the single muscle fiber. A spring-mass model has been used to accurately describe and predict the whole body dynamics of runners. Runners modify their spring-like behavior as they traverse challenging surface transitions in the natural world without appearing to dramatically change their running dynamics. The underlying mechanisms and control of this spring-like behavior for natural movements of humans are still poorly understood. To investigate how runners accommodate variable terrain, I conducted a series of experiments to examine the control of whole-body spring-mass mechanics during running and the influence of different kinematics on single muscle fiber force generation. I show that runners have the flexibility to control the left leg independent from the right leg so they can traverse highly variable terrain without dramatically changing their center of mass dynamics. When each leg interacts with different surface stiffnesses, runners control the stiffness of the left leg independent from the right leg for each step. Although runners do not achieve identical dynamics from step to step, they alter leg stiffness significantly and to the same stiffness value they use on a corresponding continuous track of uniform stiffness. I also demonstrate that runners rapidly adjust leg stiffness and begin to recover their center of mass dynamics early in the first footfall on an unexpected surface. The rapid increase in leg stiffness is initiated without input from neural reflexes. The timing of changes in muscle activity and leg stiffness suggests that an immediate mechanical mechanism, rather than reflexes with an inherent delay, initiate the change in leg behavior. Because purely mechanical responses act with no delay, they are the most likely mechanisms for runners to react rapidly to disturbances. Finally, I present an investigation of the mechanisms behind the long-term effects of zero-delay mechanical responses of single muscle fibers that have been shortened or shortened and stretched. The investigation suggests that non-uniformities in sarcomere length and fatigue do not play dominant roles in muscles' ability to generate different amounts of isometric force after shortening and shortening followed by stretch. As a whole, this work illustrates that understanding whole body mechanics requires knowledge of the flexibility of the neural control of the musculoskeletal system and of mechanical reactions that do not involve neural control, such as the mechanical response of muscle fibers to kinematic changes.

ISBN: 0496690450Subjects--Topical Terms:

1017835
Biology, Animal Physiology.

Spring-like behavior of the musculoskeletal system: From whole body to muscle fiber mechanics.
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100 1 $a Shigeoka, Cassie Akiko. $3 1931298
245 1 0 $a Spring-like behavior of the musculoskeletal system: From whole body to muscle fiber mechanics.
300 $a 119 p.
500 $a Source: Dissertation Abstracts International, Volume: 65-02, Section: B, page: 0513.
500 $a Chairs: Claire T. Farley; Steve L. Lehman.
502 $a Thesis (Ph.D.)--University of California, Berkeley, 2003.
520 $a The musculoskeletal system displays spring-like behavior from the whole body level to that of the single muscle fiber. A spring-mass model has been used to accurately describe and predict the whole body dynamics of runners. Runners modify their spring-like behavior as they traverse challenging surface transitions in the natural world without appearing to dramatically change their running dynamics. The underlying mechanisms and control of this spring-like behavior for natural movements of humans are still poorly understood. To investigate how runners accommodate variable terrain, I conducted a series of experiments to examine the control of whole-body spring-mass mechanics during running and the influence of different kinematics on single muscle fiber force generation. I show that runners have the flexibility to control the left leg independent from the right leg so they can traverse highly variable terrain without dramatically changing their center of mass dynamics. When each leg interacts with different surface stiffnesses, runners control the stiffness of the left leg independent from the right leg for each step. Although runners do not achieve identical dynamics from step to step, they alter leg stiffness significantly and to the same stiffness value they use on a corresponding continuous track of uniform stiffness. I also demonstrate that runners rapidly adjust leg stiffness and begin to recover their center of mass dynamics early in the first footfall on an unexpected surface. The rapid increase in leg stiffness is initiated without input from neural reflexes. The timing of changes in muscle activity and leg stiffness suggests that an immediate mechanical mechanism, rather than reflexes with an inherent delay, initiate the change in leg behavior. Because purely mechanical responses act with no delay, they are the most likely mechanisms for runners to react rapidly to disturbances. Finally, I present an investigation of the mechanisms behind the long-term effects of zero-delay mechanical responses of single muscle fibers that have been shortened or shortened and stretched. The investigation suggests that non-uniformities in sarcomere length and fatigue do not play dominant roles in muscles' ability to generate different amounts of isometric force after shortening and shortening followed by stretch. As a whole, this work illustrates that understanding whole body mechanics requires knowledge of the flexibility of the neural control of the musculoskeletal system and of mechanical reactions that do not involve neural control, such as the mechanical response of muscle fibers to kinematic changes.
590 $a School code: 0028.
650 4 $a Biology, Animal Physiology. $3 1017835
650 4 $a Biophysics, General. $3 1019105
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710 2 0 $a University of California, Berkeley. $3 687832
773 0 $t Dissertation Abstracts International $g 65-02B.
790 1 0 $a Farley, Claire T., $e advisor
790 1 0 $a Lehman, Steve L., $e advisor
790 $a 0028
791 $a Ph.D.
792 $a 2003
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3121694