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Length-Tension Relation in Skeletal Muscles

How does the force of a muscle relate to its length? The force a muscle can exert depends on several factors, including the cross-sectional area of the muscle (how many fibers it has) and the way in which the muscle is attached to the skeleton. A third factor is degree of extension of the muscle. When a muscle is relaxed the maximum number of cross-bridges between filaments are available for contraction. The muscle is able to exert the greatest amount of force in this state. If the muscle is contracted then filament movement is hampered because of proximity to the Z lines. If the muscle is over-extended then fewer cross-bridges are available to move the filaments.

View the animation below, then complete the quiz to test your knowledge of the concept.






1The force of contraction is greatest for a muscle fiber...
A)at 100% of its relaxed length.
B)less than 100% of its relaxed length.
C)greater than 100% of its relaxed length.
D)A and B.
E)B and C.



2The force of contraction is lowest for a muscle fiber...
A)at 100% of its relaxed length.
B)less than 100% of its relaxed length.
C)greater than 100% of its relaxed length.
D)A and B.
E)B and C.



3The rate of change of percent maximum tension for muscle fibers is greatest from...
A)60% - 80% of relaxed length.
B)80% - 100% of relaxed length.
C)100% - 120% of relaxed length.
D)120% - 140% of relaxed length.
E)140% - 160% of relaxed length.



4The muscle fiber length and the amount of force exhibited by the muscle fiber are inversely proportional when the muscle fiber is longer than its relaxed length.
A)True
B)False



5The muscle fiber length and the amount of force exhibited by the muscle fiber are directly proportional when the muscle fiber is shorter than its relaxed length.
A)True
B)False







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