LEADER 00000nam  2200337   4500 
001    AAI3146957 
005    20051010101559.5 
008    051010s2004                        eng d 
020    0496053051 
035    (UnM)AAI3146957 
040    UnM|cUnM 
100 1  Moholkar, Nitin Manohar 
245 10 Determinants of leg stiffness and preferred stride 
       frequency in bouncing gaits 
300    78 p 
500    Source: Dissertation Abstracts International, Volume: 65-
       09, Section: B, page: 4700 
500    Chairs:  Tony M. Keaveny; Claire T. Farley 
502    Thesis (Ph.D.)--University of California, Berkeley, 2004 
520    People can easily run on a variety of terrains by 
       adjusting the stiffness of their legs. The overall goal of
       this dissertation is to understand how humans adjust leg 
       stiffness during hopping and running and to examine 
       whether people strongly prefer specific frequencies for 
       hopping and running due to the optimal role of the spring-
       like mechanics of the leg. To accomplish these goals, I 
       investigated humans hopping on two legs vs hopping on one 
       leg, running at a range of stride frequencies at a fixed 
       speed, and hopping at a range of frequencies. When humans 
       hop on one leg, they make their leg 59% stiffer than when 
       they hop on two legs. Leg stiffness is most sensitive to 
       changes in ankle stiffness and increased due to a stiffer 
       ankle and a smaller moment arm of the ground reaction 
       force about the ankle. In contrast, during running, leg 
       stiffness is most sensitive to knee mechanics. Runners 
       make their leg 96% stiffer to increase stride frequency 
       primarily by stiffening the knee and decreasing the moment
       arm of the ground reaction force about the knee. The 
       mechanisms to adjust leg stiffness differ due to the 
       moment arm of the ground reaction force being longest 
       about the ankle in hopping and about the knee in running. 
       In the final study, I find that the leg does not behave 
       most like a spring at the preferred frequencies for 
       hopping and running. Rather, it becomes more spring-like 
       as frequency increases. Thus, springlike leg behavior does
       not cause the minimization of metabolic energy cost at the
       preferred frequency. Overall, these studies emphasize the 
       role of springlike leg mechanics and the importance of leg
       stiffness adjustment in hopping and running. Moreover, due
       to different leg geometries, hoppers and runners use 
       different strategies for leg stiffness adjustment 
590    School code: 0028 
590    DDC 
650  4 Engineering, Biomedical 
650  4 Health Sciences, Recreation 
690    0541 
690    0575 
710 20 University of California, Berkeley 
773 0  |tDissertation Abstracts International|g65-09B 
856 40 |uhttp://pqdd.sinica.edu.tw/twdaoapp/servlet/