(1) Calculate the reactive force and reactive muscle moment at the knee for a seated leg extension, with a weight of 35, 45, and 55 lbs. Assume that the leg is held at an angle 8.
(2) A subject is walking across a force plate in a gait lab, where kinematic and kinetic data are collected.
a. Assuming the angular acceleration of each body and the ground reaction forces at heel strike are known, write the equations to calculate the reaction forces and moments at the ankle, knee and hip.
b. What other information is necessary or missing?
c. Assuming that the subject is a 50th percentile female, do you have the information needed to solve for the reaction forces? Create and complete a table listing the information for each variable (example table started below, in no particular order).
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Variable Description
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Variable Name
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Known? Unknown?
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Value/symbol if known
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Source of data
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Length of lower leg
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LLL
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Known
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LLL = 37.16 cm
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Table 3.8 in Chaffin
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Acceleration of lower leg
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aLL
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Known
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aLL
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Kinematic data from motion analysis system
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Reaction force at ankle (x-direction)
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Fax
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Unknown
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Fax
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