Study Notes on Kinesiology Mechanics

Introduction to Kinesiology Mechanics

  • Definition and significance of kinesiology.

    • Etymology: Derived from Greek roots

    • "kinesia" (movement) + "ology" (study of a subject).

    • Kinesiology as a multidisciplinary science encompassing:

    • Musculoskeletal system

    • Nervous system

    • Respiratory system

    • Circulatory system.

    • Focus on how the body responds to internal and external forces.

    • Importance of integrated knowledge for understanding human movement.

Understanding Kinesiology Scope

  • Integration of multiple physiological systems necessary for movement:

    • Musculoskeletal system provides physical support (bones as levers, joints as fulcrums, muscles as engines).

    • Nervous system coordinates and controls muscle actions, ensuring purposeful movements.

    • Respiratory and circulatory systems supply energy and remove waste, critical for muscle function.

  • Recognition that limitations in heart or lungs affect mobility as much as musculoskeletal limitations.

Fundamental Forces in Human Movement

  • Muscular Force:

    • Internal power generated through muscle contraction.

    • Types of Contractions:

    • Concentric Contraction:

      • Muscle shortening, generating upward motion, e.g. lifting limbs.

    • Eccentric Contraction:

      • Muscle lengthening under tension, acting as a brake against gravity, e.g. lowering oneself into a seat.

  • Gravitational Force:

    • Constant downward pull of Earth affecting body segments.

    • Interaction with muscular force for both movement and control.

  • Frictional Force:

    • Resists movement, essential for stability and propulsion.

    • Example: Walking requires friction between shoes and ground to prevent slipping.

  • Tensile Force:

    • Resistance from biological structures when subjected to stretching.

    • Components: ligaments and joint capsules providing stability and protecting against excessive movement.

The Concept of Tensile Force

  • Definition of Tensile Force:

    • Internal resistance to stretching in connective tissues.

    • Critical for joint stability and protection against injury.

    • Ligament analogy: high tension cable resisting joint displacement.

Joint Stability and Packing Positions

  • Closed Pack Position:

    • Joint structures maximally stretched, providing high stability, minimal accessory motion.

    • Best for resisting external forces; less mobility.

  • Loose Pack Position:

    • Ligaments relaxed, allowing greater movement.

    • Provides necessary mobility but at the cost of joint stability.

    • Understanding joint packing essential for clinicians to balance stability and mobility.

Joint Cohesion Factors

  • Cohesion:

    • Forces and structures maintaining joint alignment under stress.

    • Critical structures include:

    • Ligaments: Fibrous tissue connecting bones, limiting excessive movement.

      • Different types: collateral ligaments provide medial/lateral stability.

    • Joint Capsule: Fibrous structure enclosing joint cavity, assisting in stability.

Muscle Tension in Joint Cohesion

  • Active role of muscle tension in joint stability particularly in shallow socket joints (e.g., shoulder).

  • Tendons:

    • Connect muscles to bones, contributing to joint stability through tensile resistance.

  • Fascia:

    • Elastic connective tissue enclosing muscles, providing containment and structural support.

Non-Obvious Factors Affecting Joint Stability

  • Negative Pressure:

    • Vacuum effect in some joints (e.g., hip) aiding in joint cohesion.

  • Weight Bearing:

    • Compression of joint surfaces increasing stability during movement.

Mechanics Facilitating Joint Movement

  • Muscle Contraction:

    • Driving factor for joint movement, dictated by line of pull.

    • Relationship between attachment points defines movement direction.

  • Joint Structures:

    • Geometry of joints constrains possible motion (e.g., hinge vs. ball-and-socket).

      • Hinge joint (elbow) allows motion along one axis.

      • Ball-and-socket joint (shoulder) allows multi-axis motion, increasing mobility but decreasing stability.

Reducing Friction in Joint Movement

  • Hyaline Cartilage:

    • Smooth tissue lining bones in joints, critical for low-friction movement.

    • Lacks blood supply; health maintenance is crucial.

  • Synovial Fluid:

    • Viscous fluid that lubricates joints and reduces friction.

    • Its viscosity changes with movement; aids in joint efficiency.

  • Bursae:

    • Fluid-filled sacs acting as cushions between moving structures and bony prominences.

    • Categories based on location (tendon-bone, skin-bone interfaces).

Clinical Application: Manual Muscle Testing (MMT)

  • Purpose:

    • Assessment tool for evaluating muscle strength and recruitment by the nervous system.

  • Types of Muscle Testing:

    • Gross Muscle Testing:

    • Evaluates strength of muscle groups performing collective actions, used early in rehabilitation.

    • Fine Muscle Testing:

    • Isolates individual muscles for a sensitive assessment of nerve and muscle integrity.

Grading Manual Muscle Testing

  • Grading system assessing:

    • Body position relative to gravity.

    • Available range of motion under gravity.

    • Manual resistance from the clinician.

  • Grading Scale:

    • Grade 0: No visible contraction

    • Grade 1: Flicker of contraction, no movement

    • Grade 2: Full range in gravity eliminated position (poor grade)

    • Grade 3: Full range against gravity (fair grade)

    • Grade 4: Full range against gravity with moderate resistance (good grade)

    • Grade 5: Full strength against maximal resistance (normal grade)

  • Documentation of results as fractions or letters, supported by observations of pain or compensatory movements.

Nuances in Muscle Grading

  • Key distinctions among grades (particularly poor and fair) vital for tracking progress.

  • Importance of comprehensive documentation and communication with patients during assessments.