Introduction to Kinesiological Concepts in Physical Therapy

Kinesiology

The study of movement

Biomechanics

The application of the principles of mechanics to the study of biological systems

Kinematics

The set of concepts that describes the motion of a body, without regard to the forces that cause that motion.

Kinetics

The description of the effects of forces on the body

Linear motion

Translation: All parts of the body move parallel and in the same direction as every other part of the body.

Angular motion

Rotation: A rigid body moves in a circular path around a pivot point. All points move in the same direction (clockwise or counterclockwise). Motion is measured in degrees or radians.

Osteokinematics

The motion of bones relative to the three cardinal planes of the body: sagittal, frontal and horizontal.

Sagittal Plane

Common motion in this plane is flexion/extension.

Frontal (Coronal) Plane

Common motion: abduction/adduction.

Transverse (Horizontal) Plane

Internal/external rotation.

Axes of Motion

Usually located through the convex bone of the joint. Axes run perpendicular to the plane of motion.

X-axis

Medial-lateral axis.

Y-axis

Superior-inferior axis.

Z-axis

Anterior-posterior axis.

Degrees of Freedom

The number of planes through which a joint can be voluntarily moved.

Glenohumeral joint

Movement in 3 planes.

Instantaneous Axis of Rotation

Not stationary; moves slightly throughout the motion.

Open Chain

One joint can move independently of the others; the distal segment is free to move; usually NWB

Closed Chain

Distal end of the chain is fixed or stabilized on a support surface and motion occurs at the proximal segments; usually WB

Forces

Internal forces and external forces that can make us move

Body Weight

A type of external force calculated as Force = mass x acceleration (F=m x a) or Weight = mass x gravity (W=m x g)

Gravity

The force that pulls objects toward the center of the Earth

Center of Mass

Point where the mass is evenly distributed in all directions

Center of Gravity

Point in the body through which the resultant force of gravity acts

Line of Gravity

Always vertically downward from the Center of Mass (COM)

Base of Support

The area beneath an object or person that includes every point of contact that the object or person makes with the supporting surface

Tissue Mechanics

The mechanics of materials of human connective tissue (bones, ligaments, cartilage, and tendons)

Load

In tissue mechanics, we refer to force as a load

Types of Load

Tension, Compression, Bending, Shear, Torsion

COM Location

Each body segment has a Center of Mass (COM) approximately at the midpoint of the segment

COM Variation

The COM of the body or the lower extremity will change depending upon the spatial orientation of the individual segments