Kinesiology and Biomechanics

Kinesiology

The study of human movement.

Biomechanics

The application of mechanics to human movement.

Optimize performance, prevent injury, restore function.

Goals of biomechanics

Planes of motion

Frontal (Coronal), Sagittal, Transverse (Horizontal).

Movements in the frontal plane

Abduction, adduction, lateral flexion, radial/ulnar deviation, inversion/eversion.

Movements in the sagittal plane

Flexion, extension, dorsiflexion, plantar flexion.

Movements in the transverse plane

Rotation, pronation, supination, horizontal abduction/adduction.

Agonist muscle

The prime mover responsible for motion.

Antagonist muscle

The muscle that opposes movement.

Stabilizer muscle

A muscle that holds a joint steady.

Neutralizer muscle

A muscle that prevents unwanted movement.

Law of Inertia

An object remains at rest or in motion unless acted upon by an external force.

Law of Acceleration

→ Force = Mass × Acceleration (F = ma).

Example: A heavier barbell requires more force to lift.

Law of Action-Reaction

→ For every action, there is an equal and opposite reaction.

Osteokinematics

The study of bone movement at a joint.

Arthrokinematics

The study of small joint movements (roll, glide, spin).

Concave-convex rule

Convex on concave → Moves in the opposite direction. Concave on convex → Moves in the same direction.

Active Range of Motion (AROM)

Movement performed by the individual using their own muscles.

Passive Range of Motion (PROM)

Movement assisted by an external force.

Factors affecting ROM

Joint structure, ligament elasticity, muscle tightness, pain, injury.

Force

A push or pull that causes displacement.

Net force

The overall effect of all forces acting on a body.

weight (W)

= mass × gravity (9.81 m/s²).

Torque (T)

The rotational force applied to an object

Compression

A squeezing force on the body

Tension

A pulling force (e.g., muscles pulling on bones).

Shear

A sliding force (e.g., knee joint during landing).
* force parallel to surface

Torsion

A twisting force (e.g., pronation & supination of the forearm).

Three types of levers

First-class (EAR), Second-class (ERA), Third-class (REA).

First-class lever (EAR) example

Seesaw, head nodding.

Second-class lever (ERA) example

Plantar flexion (calf raise).

Third-class lever (REA) example

Bicep curl (most common in the body).

Open Kinematic Chain (OKC)

Distal end moves freely (e.g., leg extension).

Closed Kinematic Chain (CKC)

Distal end is fixed (e.g., squats, push-ups).