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Muscle biomechanics

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Brief description of muscle Bio mechanics for Physiotherapists

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Muscle biomechanics

  1. 1. Muscle biomechanics Prof Subhash M Khatri
  2. 2. Motors
  3. 3. 1 January 1680 Giovanni Alfonso BorelliDe Motu Animalium book
  4. 4. Overview• Mouse 640• Organ of MVT• Largest TIB• 40-45% of TBW• Respiration, circulation, digestion, locomotion, communication
  5. 5. Classification• Red &white:Red muscles contract slowly & white muscle/skeletal contracts fastly• Tonic & Phasic:Tonic/postural performs continuous low level of contractile activity & phasic short durated high level.
  6. 6. Classification• Contractors& Expanders: Pulls the body in approximate fetal positione.g flexors, adductors, medial rotators. Expanders open up the body e.g. extensors, abductors, lateral rotators.• Spurt & shunt: Muscle which attaches closer to the joint axis has larger rotatory component & is called spurt muscle
  7. 7. Fs FFr
  8. 8. Mechanics• Rotatory component & Stabilizing component• Angle formed by the mechanical axis of muscle with lever arm in which it is inserted• Fr= F sin8• Fs=F cos 8• Both components equal if angle is 450 =0.70• Most of muscle angles very small & hence stabilizing component is >rotatory hence position ,balance& stabilization is maintained very well.
  9. 9. PCA• Fm = (Amcosθ)σm• where Fm = max isometric contraction force Amcosθ = physiological cross-sectional area θ = angle of pennation σm = maximum isometric stress
  10. 10. Series and parallel elastic elements in muscle.A.Resting muscle contains elastic elements in series with the contractile elements (sarcomeres) andin parallel with them.B.During an isometric contraction, the muscle does not change length, but sarcomeres shorten,stretching the series elastic elements.C.During isotonic contraction, the contractile elements shorten, stretching the series elasticelements, before they develop tension to lift the load.D.Muscle begins to shorten when contractile elements shorten further.
  11. 11. Muscle can fail to produce force when slack (active insufficiency) and can restrict range of motion when fully stretched (passive insufficiency).
  12. 12. When a muscle develops concentric tension against a high load, the velocity of muscle shortening must be relatively slow.
  13. 13. In single muscle fibers and isolated muscle preparations, force generation is at its peak when the muscle is at normal resting length (neither stretched nor contracted).
  14. 14. FORCE TIME RELATIONSHIPMuscular power - the product of force and velocity.Maximum power occurs at approximately one-third ofmaximum velocity and at approximately one-third ofmaximum concentric force.Muscular endurance - the ability of the muscle to exerttension over a period of time. Effect of muscle temperature - as body temperature elevates, the speeds of nerve and muscle functions increase.
  15. 15. Rundown1. Force time relationship2. Length tension relationship3. Length tension curve/stress & strain curve4. Force velocity curve5. Force & cross sectional area6. Rotatory & stabilizing components

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