Introduction to Kinesiology: Quick Reference

  • Planes of Motion
    • Sagittal plane: divides body into right and left; includes midline (midsagittal); flexion and extension movements
    • Frontal (Coronal) plane: divides body into anterior and posterior; abduction and adduction movements
    • Transverse plane: divides body into inferior and superior; rotary movements
  • Axes of Motion
    • Joints rotate about axes of motion
    • Frontal axis: medial to lateral
    • Sagittal axis: anterior to posterior
    • Vertical axis: inferior to superior
  • Planes and Axes quick relations
    • Each plane movement occurs around a corresponding axis
  • Kinetic Chains
    • Closed-chain movement: proximal segment moves in relation to fixed distal segment; promotes stabilization
    • Open-chain movement: distal segment moves freely; promotes mobility
  • Force and Levers
    • Force: any push or pull on matter
    • Tensile force: pulling; Compressive force: pushing
    • Moment (torque): turning effect of force; extMoment=extForceimesextMomentarmext{Moment} = ext{Force} imes ext{Moment arm}
    • Action: specific muscle motion at a joint
    • Moment arm: distance from joint axis to line of force
    • Mechanical advantage: extMechanicaladvantage=extOutputforceextInputforceext{Mechanical advantage} = \frac{ ext{Output force}}{ ext{Input force}}
    • Joint reaction force: internal response within a joint to external forces; related to internal vs external moment arms
  • Levers in the Body
    • First-class lever: force and resistive force on opposite sides of axis (e.g., cervical spine)
    • Second-class lever: resistive force closer to axis; same side relative to axis (e.g., ankle)
    • Third-class lever: most common in body; favors speed/velocity (e.g., shovel use)
  • Stress and Strain
    • Stress: force per area; extStress=FAext{Stress} = \frac{F}{A}
    • Strain: relative deformation; extStrain=extΔLL0ext{Strain} = \frac{ ext{Δ}L}{L_0}
    • Elasticity: ability to return to original shape after deformation
    • Young’s modulus: material stiffness; represented on stress–strain diagram
  • Biomechanical Properties of Body Tissue
    • Biomechanics: structure, function, and motion of biological systems
  • Biomechanics of Bone
    • Cortical bone: high mineral content; shaft of long bones; rigid support
    • Cancellous (spongy) bone: higher collagen content; trabecular architecture near marrow and ends
  • Articular Cartilage and OA
    • Articular cartilage: dense connective tissue at ends of long bones; cushions joint
    • Osteoarthritis: cartilage degeneration within a joint
  • Biomechanics of Ligaments and Tendons
    • Ligaments: bone-to-bone; joint stability
    • Tendons: muscle-to-bone; transmit force
    • Joint capsule: dense fibrous sleeve with synovial fluid; passive stability
    • Aponeurosis: fibrous insertion (e.g., rectus sheath)
  • Biomechanics of Muscle
    • Three tissue types: skeletal (striated), cardiac, smooth
  • Skeletal Muscle Structure
    • Skeletal muscle: moves bones; striated fibers
    • Histology layers: endomysium (around fibers), perimysium (around fascicles), epimysium (around groups of fascicles)
    • Myofibrils and sarcomeres: contractile units; actin and myosin form the filaments; titin stabilizes the sarcomere
  • Muscle Design and Strength
    • PCSA (physiological cross-sectional area): area of muscle cross-section; strength proportional to PCSA
    • Fiber orientation: pennate (oblique) vs fusiform (parallel to line of force)
  • Neuromuscular Control
    • A muscle comprises many motor units; all-or-none activation at sarcomeres
    • Fascia and noncontractile tissue; balance of flaccidity and hypertonia
  • Regulation of Muscle Tone
    • Muscle spindles: sense changes in length; provide length information and stretch reflex
    • Phasic stretch reflex: activates agonist muscle
    • Golgi tendon organs: at muscle–tendon junction; detect tension; more sensitive than spindles
  • Muscle Fibers and Types
    • Slow-twitch (Type I): low force; fatigue resistant
    • Fast-twitch (Type II): high force; faster fatigue
  • Muscle Actions and Coordination
    • Agonist: prime mover
    • Antagonist: opposite motion
    • Fixators: stabilize origin
    • Synergists: assist prime mover
    • Force couple: muscles that work together in different directions to produce a motion or stabilize a joint
  • Single- vs Multi-Joint Muscles
    • Some cross one joint (e.g., brachialis); some cross multiple joints (e.g., FDP)
    • Example: FDP crosses wrist and finger joints to contribute to multiple flexion actions
  • Muscle Contractions
    • Isometric: no length change
    • Isotonic: length changes with joint motion
    • Eccentric: lengthening
    • Concentric: shortening
  • Load Rate and Insufficiency
    • Load rate: speed of force application
    • Passive insufficiency: muscle cannot lengthen enough to allow full ROM
    • Active insufficiency: muscle cannot shorten further at the cross joints
  • Joints: Design and Function
    • Joint (articulation): bones connect via synovial, fibrous, or cartilaginous joints
    • Synovial joints: mobile; fibrous joints: little mobility; cartilaginous joints: stability with limited mobility
  • Close-Pack vs Open-Pack Joints
    • Close-pack: maximal joint surface contact; maximal ligament tension
    • Open-pack: minimal contact; greater laxity; more mobility
  • Ball-and-Socket Joint
    • Spherical surface fits into a socket; most mobile; three-axis rotation (e.g., glenohumeral)
  • Ellipsoid Joint
    • Oval-convex to elliptical concave; two-axis motion (e.g., radiocarpal)
  • Hinge Joint
    • One axis; flexion/extension; collateral ligaments stabilize; e.g., humeroulnar
  • Saddle Joint
    • Modified ellipsoid; two axes; e.g., CMC of thumb
  • Gliding Joint
    • Flat surfaces; least movement; translation; e.g., carpal bones
  • Pivot Joint
    • One axis; rotation around another; e.g., atlantoaxial joint
  • Osteokinematics and Arthrokinematics
    • Osteokinematics: gross bone motion relative to each other
    • Arthrokinematics: joint surface motions (accessory motions) not produced by voluntary muscle action
    • Translation: gliding; compression; distraction; spin
  • Arthrokinematics Rules
    • Convex-on-concave: distal bone glides opposite to joint rotation (e.g., wrist flexion: dorsal carpal glide while flexing)
    • Concave-on-convex: distal bone glides with the rotation
    • Examples: wrist (convex-on-concave) vs MCP joints (concave-on-convex)