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IPHY 4540 Biomechanics

IPHY 4540 Biomechanics. Objective: to learn how to quantitatively analyze the mechanical function of the human musculoskeletal system using principles of physics and physiology. Topics: Functional Anatomy Tissue Biomechanics (muscle, tendon, bone) Movement (kinematics)

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IPHY 4540 Biomechanics

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  1. IPHY 4540 Biomechanics • Objective: to learn how to quantitatively analyze the mechanical function of the human musculoskeletal system using principles of physics and physiology. • Topics: • Functional Anatomy • Tissue Biomechanics (muscle, tendon, bone) • Movement (kinematics) • Movement dynamics (kinetics) • Whole body, muscle and joint forces • Impulse, Momentum • energy, power • torque

  2. Outline • Functional Anatomy • Muscle actions • Lever systems in the body

  3. Functional Anatomy • the study of body components needed to achieve or perform a human movement or functions. • Care about movement produced by muscle group, not muscle location

  4. Functional Anatomy Hammill J, Biomechanical Basis of Human Movement

  5. Terms • superior • Inferior • anterior • posterior • medial • lateral • proximal • distal • superficial • deep • unilateral • ipsilateral • contralateral • bilateral Hammill J, Biomechanical Basis of Human Movement

  6. Functional Anatomy • Reference System • origin • axes • planes • Planes • Frontal • Vertical • Anterior/posterior parts • Sagittal • Vertical • Left/right parts • Transverse • Horizontal • Superior/inferior Hammill J, Biomechanical Basis of Human Movement

  7. Functional Anatomy • Reference System • origin • axes • planes • Planes • Frontal • Vertical • Anterior/posterior parts • Sagittal • Vertical • Left/right parts • Transverse • Horizontal • Upper/lower Hammill J, Biomechanical Basis of Human Movement

  8. Axes: • Longitudinal (Twist): • head to toe • Mediolateral (Somersault) • Left to right • Anteroposterior (Cartwheel) • Front to back

  9. The knee

  10. Muscle Actions • Motors that move our limbs • Example: • Push-up • Which muscle? • Which joint? • Flexion/extension? • Leg curl

  11. Muscle Actions Muscles: - only exert pulling forces - 3 actions: can exert force and -shorten (shortening/concentric) -stay the same length (isometric) -be lengthened or resist stretching (lengthening/eccentric) • when not activated, muscles can be passively lengthened by other forces

  12. Shortening Muscle Actions Isotonic = constant force (artificial) Isovelocity = constant velocity (artificial) Neither, i.e. variable force and velocity (most common)

  13. Isometric Muscle Actions Muscle produces force, but does not overcome external load, so no movement develops. Very common: examples?

  14. Lengthening Muscle Actions Muscles only exert pulling force, But the opposing force can be greater than the muscle force, forcibly stretching the muscle. Also very common. High Risk for injury Examples:

  15. Leg press example • What is the primary muscle involved? • Describe its actions throughout one cycle.

  16. Muscle Actions - only exert pulling forces - 3 actions: can exert force and -shorten (shortening/concentric): force>load -stay the same length (isometric): force=load -be lengthened or resist stretching (lengthening/eccentric) force<load Force = load Force < load Force > load Force Load

  17. Outline • Functional Anatomy • Muscle actions • Lever systems in the body

  18. Levers • A method of transmitting force • Amplify force • Amplify velocity • Amplify movement distance • Muscles use leverage to generate movement

  19. Levers • 4 components • Lever (bone) • Fulcrum (pivot point, joint)) • Effort force (muscle force) • Load force (external forces) effort load lever fulcrum

  20. Levers: The Law • Law of Levers: • Fload x rload = Feffort x reffort • r is the distance to the forces “Give me a lever and I shall move the earth” – Archimedes Mechanical Advantage: Fload/Feffort > 1, rload < reffort Mechanical Disadvantage: Fload/Feffort < 1, rload > reffort

  21. Levers: The Law • Fload rload = Feffort reffort A vs B: Mechanical Advantage or Disadvantage? Fload/Feffort = ? 100kg F A rload=1m Feffort=my laptop (2kg) B

  22. Levers: 3 classes Don’t worry about first, second, third class Do understand: fulcrum = joint = pivot The relative positions of muscle force, joint and load are important. What is being amplified? Force or velocity

  23. 3 classes of levers Classes of Levers • 1st Class— see-saw • 2nd Class—Wheelbarrow • 3rd Class—Tweezers

  24. Levers: Force and Velocity • Fload x rload = Feffort x reffort • Class 1 • Fload x rload = Feffort x reffort • If rload>reffort • Fload< Feffortvelocity amplifier • If rload<reffort • Fload>Feffort  force amplifier

  25. 1st Class Levers Muscle joint load (MJL) Load joint Muscle (LJM)

  26. 1st Class Lever Muscle joint load e.g. triceps acting at the elbow Velocity or force magnifier?

  27. 1st Class Levers Muscle joint load e.g. your head is tilting forward (e.g. sleeping) Muscles on the back of the neck pull

  28. 1st Class Levers (MJL) in the body Amplify velocity of joint extension

  29. 1st Class Levers (MJL) tools Can amplify force or velocity depending on length of the lever e.g. tool that amps force using 1st class lever

  30. 1st Class Levers (MJL) tools Can amplify force or velocity depending on length of the lever e.g. tool that amps velocity using 1st class lever

  31. Class 3 levers (JML) • Fload x rload = Feffort x reffort • Class 3 • Fload x rload = Feffort x reffort • rload>reffort • Fload< Feffortvelocity amplifier Joint Muscle Load

  32. 3rd Class Levers joint muscle load

  33. 3rd Class Levers joint muscle load e.g. hold weight in your hand, biceps pulls up

  34. 3rd Class Levers (JML) tools Can only amplify velocity e.g. field hockey stick, golf putter, shovel

  35. Class 2 levers (JLM) • Class 2 • Fload x rload = Feffort x reffort • rload<reffort • Fload> Feffortforce amplifier Rare in the body Jaw joint (using molars) is a good example Any others? Joint Load Muscle

  36. 2nd Class Levers (JLM) tools Can only amplify force e.g. nut cracker

  37. Summary Classes of Levers • 1st Class— see-saw, push-up • Muscle-Joint-Load • Force or Velocity amplifier, depending on the lever arm • 2nd Class—Wheelbarrow • Joint-Load-Muscle • Force Amplifier • 3rd Class—Tweezers, biceps-curl • Joint-Muscle-Load • Velocity Amplifier

  38. Why do we usually see 3rd class levers in the body? OR • Why do we have short muscle arms?

  39. Anatomical Terms • Joint Position • To discuss joint position we define joint angle • joint angle: relative angle between two segments • Joint Movement • Flexion: relative angle (joint angle) decreases • Extension: relative angle increases (straightening movement) Hammill J, Biomechanical Basis of Human Movement

  40. More muscle terms agonist muscles creating the same joint movement antagonist muscles opposing or producing the opposite joint movement must relax to allow a movement to occur OR contract to slow a movement down example: kicking co-contraction

  41. 1 joint vs. 2 joint muscles Examples of 1 joint muscles: Examples of 2 joint (biarticular) muscles:

  42. Biarticular muscles • Advantages

  43. How do we stand up from a chair? Joint actions: What muscles act across the hip? What muscles act across the knee? What muscles act across the ankle? All 1-joint muscles? All 2-joint muscles?

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