Kin Exam 1

Kinesiology

The study of human movement, focusing on anatomic and biomechanical interactions within the musculoskeletal system.

Kinematics

The branch of mechanics that describes motion without considering the forces that cause it.

Translational Motion

Rectilinear (straight path) and curvilinear (curved path).

Rotation in Kinematics

Circular motion around a pivot point (axis of rotation), with orientation constantly changing.

General Motion

A combination of translation and rotation.

Active Motion

caused by muscle contraction

Passive motion

caused by external forces like gravity or another person

Planes of Motion and Axes

Sagittal → medial-lateral axis; Frontal → anterior-posterior axis; Horizontal → vertical axis.

Degrees of Freedom in Joints

The number of independent directions of movement allowed at a joint.

Arthrokinematics

The motion between articular surfaces of joints (roll, slide, spin).

Convex-Concave Rule

Convex-on-concave → roll and slide opposite; Concave-on-convex → roll and slide in same direction.

Closed-Packed Joint Position

most stable fit of surfaces, ligaments taut

Loose-Packed Joint Position

slack ligaments, more accessory movement.

Torque

A rotary force causing angular motion, equal to force × moment arm.

Muscle Activation Types

Isometric (no length change), Concentric (shortening), Eccentric (lengthening).

Lever in Biomechanics

A rigid rod across a fulcrum; body uses 1st, 2nd, and 3rd class levers.

Arthrology

The study of joint classification, structure, and function.

Main Joint Categories by Movement Potential

Synarthroses (little/no movement) and Diarthroses (freely movable, synovial).

Examples of Fibrous Joints

Skull sutures, distal tibiofibular joint.

Examples of Cartilaginous Joints

Symphysis pubis, intervertebral discs.

Seven Elements of Synovial Joints

Capsule, synovial membrane, cartilage, sensory nerves, synovial fluid, ligaments, blood vessels.

Synovial Joint Types with DOF

Plane (0), Hinge (1), Pivot (1), Ellipsoid (2), Saddle (2), Condyloid (2), Ball-and-socket (3).

Periarticular Connective Tissues (PCT)

Capsule, ligament, tendon, cartilage, and fibrocartilage.

Main Fibrous Proteins in PCT

Collagen (Type I = stiff, Type II = framework) and elastin (stretchy).

Collagen

Type I = stiff, Type II = framework

Elastin

Stretchy fibrous protein

Wolff's Law

Bone is laid down in areas of high stress and resorbed in areas of low stress

Compact bone

Outer cortex of bone

Cancellous bone

Inner portion of bone

Sarcomere

Basic functional unit of muscle (actin + myosin)

Actin

Thin filament in muscle

Myosin

Thick filament that binds to actin to produce force

Titin

Structural protein that produces passive tension when stretched

Pennation angle

Angle between muscle fibers and tendon; affects force transmission

Fusiform muscles

Muscles with fibers arranged parallel

Pennate muscles

Muscles with oblique fibers, allowing more fibers and greater force

Passive tension

Resistance when muscle is stretched

Active tension

Produced by crossbridge cycling in muscle

Sliding filament theory

Muscles shorten when actin and myosin slide past each other

Force-velocity curve principle

Concentric force decreases with faster shortening; eccentric force increases with faster lengthening

Motor unit

A single motor neuron and the muscle fibers it innervates

Henneman's size principle

Motor units are recruited from smallest (slow-twitch) to largest (fast-twitch)

Electromyography (EMG)

Recording and interpreting electrical activity from activated skeletal muscle

Muscle fatigue causes

ATP depletion, glycogen loss, increased hydrogen ions, reduced motor unit activity

Hypertrophy

Increase in muscle size

Atrophy

Decrease in muscle size from disuse

Biomechanics

The study of forces applied to the body and its reaction

Newton's 1st Law (Inertia)

A body stays at rest or uniform motion unless acted on by external force/torque

Newton's 3rd Law (Reaction)

For every action, there is an equal and opposite reaction

Free body diagram (FBD)

A simplified sketch showing all forces acting on a body segment

Coordinate system

Used to specify the location of a point or segment (2D or 3D Cartesian)

Vector resolution

Breaking down a vector into perpendicular components

Static analysis

System in equilibrium (no acceleration)

Dynamic analysis

Includes acceleration

Force plate

Device to measure ground reaction force

Isokinetic dynamometer

Measures external torque while keeping constant angular velocity

Anthropometry

Measures body design features like mass, length, and center of mass