Length Tension Relationship

The strength of a muscle's contraction is influenced by a variety of factors. These include the number of fibers within the muscle that are stimulated to contract, the frequency of stimulation, the thickness of each muscle fiber (thicker fibers have more myofibrils and thus can exert more power), and the initial length of the muscle fibers when they are at rest.

There is an "ideal" resting length for striated muscle fibers. This is the length at which they can generate maximum force. When the resting length exceeds this ideal, the overlap between actin and myosin is so small that few cross bridges can attach. When the muscle is stretched to the point that there is no overlap of actin with myosin, no cross bridges can attach to the thin filaments and the muscle cannot contract.

Force Velocity Curve

■ Figure 12.19 Force-velocity curve. This graph illustrates the inverse relationship between the force opposing muscle contraction (the load against which the muscle must work) and the velocity of muscle shortening. A force that is sufficiently great prevents muscle shortening, so that the contraction is isometric. If there is no force acting against the muscle contraction, the velocity of shortening is maximal (Vmax). Since this cannot be measured (because there will always be some load), the estimated position of the curve is shown with a dashed line.

Fox: Human Physiology, Eighth Edition

12. Muscle: Mechanisms of Contraction and Neural Control

Text

© The McGraw-Hill Companies, 2003

Chapter Twelve

Length Tension Relationship

60 80 100 120 140

Percentage rest length

60 80 100 120 140

Percentage rest length

■ Figure 12.20 The length-tension relationship in skeletal muscles. Maximum relative tension (1.0 on the y axis) is achieved when the muscle is 100% to 120% of its resting length (sarcomere lengths from 2.0 to 2.25 |m). Increases or decreases in muscle (and sarcomere) lengths result in rapid decreases in tension.

When the muscle is shortened to about 60% of its resting length, the Z lines abut the thick filaments so that further contraction cannot occur.

The strength of a muscle's contraction can be measured by the force required to prevent it from shortening. Under these isometric conditions, the strength of contraction, or tension, can be measured when the muscle length at rest is varied. Maximum tension of skeletal muscle is produced when the muscle is at its normal resting length in vivo (fig. 12.20). If the muscle were any shorter or longer than its normal length, in other words, its strength of contraction would be reduced. This resting length is maintained by reflex contraction in response to passive stretching, as described in a later section of this chapter.

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Responses

  • Kristian
    What is the relationship between the load on a muscle and its strength of contraction?
    8 years ago
  • marco
    What is maximal resting length?
    8 years ago
  • timothy
    What resting muscle length produce most amount of force in muscle fibres 100/120?
    8 years ago
  • Alexander
    What is maximal tension human physi?
    8 years ago
  • jolly noakes
    What Is Length Tension Relationship?
    7 years ago
  • armas
    What is normal resting length of muscle?
    2 years ago
  • magnus hossi
    Where on this graph would there be optimal length for maximum tension?
    2 years ago
  • aurora palermo
    What is the maximum length of a skeletal muscle fiber?
    2 years ago
  • orlando
    What is length tension relationship curve?
    2 years ago
  • berilac
    What does resting length of muscles mean?
    2 years ago
  • bisrat
    Is resting length of a muscle where there is max actin myocin overlap?
    2 years ago
  • frank furst
    How does muscular contraction affect resting length of the muscle?
    2 years ago
  • kiros
    Where is a muscles optimum resting length for max crossbridge overlap?
    2 years ago
  • thomas martinez
    Is contraction strength related to initial length of the muscle fiber?
    1 year ago
  • meaza
    What is a good title for muscle tension relationship?
    6 months ago
  • selam
    What is the lengthtension relationship?
    3 months ago
  • Lynda
    Why is resting sarcomere length optimal?
    23 days ago
  • anna maria
    What is muscle length tension relationship and how does it work?
    6 days ago

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