Change in velocity of a body over time, expressed in linear (m/s^2) and angular (degrees/s^2) terms

Slight, passive, nonvolitional movements allowed in most joints (also called "joint play")

Push or pull generated by stimulated muscle

Motion caused by stimulated muscle

Muscle or muscle group that is more directly related to the initiation and execution of a particular movement

Angle formed between a tendon of a muscle and the long axis of the bone to which it inserts

Muscle or muscle group that has the action opposite to a particular agonist muscle

Motions of roll, slide, and spin that occur between the articular surfaces of joints

An imaginary line extending through a joint about which rotation occurs (also called the pivot point or the center of rotation)

Angular motion of an object in a direction perpendicular to its longitudinal axis, often used to describe a motion in the horizontal plane

Effort of a force that deforms a material at right angles to its long axis. A bent tissue is compressed on its concave side and placed under tension on its convex side.

A quantitative measure of a bend. Similar to a torque, a bending moment is the product of the bending force and the perpendicular distance between the force and the axis of rotation of the bend.

Point at the exact center of an object's mass (also referred to as  center of gravity when considering the weight of the mass)

Unique position within most joints of the body where the articular surfaces are most congruent, and the ligaments are maximally taut.

Activated muscle that shortens as it produces a force

A progressive strain of a material when exposed to a constant load over time

Number of independent movements allowed at a joint. A joint can have up to 3 degrees of translation and 3 degrees of rotation.

Change in the linear or angular position of an object

Type of movement in which the distal segment of a joint rotates relative to a fixed proximal segment (also called an open kinematic chain).

Movement of two objects away from one another

Activated muscle that is elongating as it is producing a force

Property of a material demonstrated by its ability to return to its original length after the removal of a deforming force

Push or pull produced by sources located outside the body. These typically include gravity and physical contact applied against the body.

Distance between the axis of rotation and the perpendicular intersection with an external force

Product of an external force and its external moment arm (also called external moment)

A push or a pull that produces, arrests, or modifies a motion

Interaction of two or more muscles acting in different linear directions, but producing a torque in the same rotary direction

Potential acceleration of a body to the center of the earth due to gravity

Resistance to movement between two contacting surfaces

Distance between the axis of rotation and the perpendicular intersection with a muscle (internal) force

Product of an internal force and its internal moment arm

Activated muscle that maintains a constant length as it produces a force

Push or pull produced by one joint surface against another, usually for the purpose of maintaining static linear equilibrium of a joint and associated bones

Branch of mechanics that describes the motion of a body, without regard to the forces or torques that may produce the motion

Series of articulated segmented links, such as the connected pelvis, thigh, leg, and foot of the lower extremity

Branch of mechanics that describes the effects of forces on the body

Relative moment arm length possessed by a particular force

Direction of a muscle's force

Direction of the gravitational pull on a body

General term that describes the application of a force to a body

Axis that extends within and parallel to a long bone or body segment

Places within most joints of the body where the articular surfaces are least congruent, and the ligaments are slackened

Quantity of matter in an object

Ratio of the internal moment arm to the external moment arm

Potential of a muscle to produce an internal torque within a particular plane of motion and rotary direction (also called joint action when referring specifically to a muscle's potential to rotate a joint).

-flexion, extension, pronation, supination, etc

Motion of bones relative to the 3 cardinal, or principal, planes

Push or pull generated by sources other than stimulated muscle, such as tension in stretched periarticular connective tissues, physical contact, and so forth

Motion produced by a source other than activated muscle

Property of a material demonstrated by remaining permanently deformed after the removal of a force

Force divided by a surface area (also called stress)

Phenomenon in which relatively low-level tension within stretched connective tissues performs a useful function

Type of movement in which the proximal segment of a joint rotates relative to a fixed distal segment (also referred to as a closed kinematic chain)

Multiple points along one rotating articular surface contact multiple points on another articular surface (also referred to as a closed kinematic chain)

Angular motion in which a rigid body moves in a circular path about a pivot point or an axis of rotation

Quantity, such as speed and temperature, that is completely specified by its magnitude and has no direction

Any part of a body or limb

Forces on a material that act in opposite but parallel directions (like the action of a pair of scissors)

Ability to dissipate forces

Single point on one articular surface contacts multiple points on another articular surface (also called glide)

Single point on one articular surface rotates on a single point on another articular surface (like a toy top)

State of a body at rest in which the sum of all foces is equal to zero

State of a body at rest in which the sum of all torques is equal to zero

Ratio of stress (force) to strain (elongation) within an elastic material

Ratio of a tissue's deformed length to its original length

Forces generated as a tissue resists deformation, divided by its cross-sectional area (also called pressure)

Two muscles that cooperate to execute a particular movement

Application of one or more forces that pulls apart or separates a material. (Also called a distraction force.) Used to denote the internal stress within a tissue as it resists being stretched.

Application of a force that twists a material about its longitudinal force

Linear motion in which all parts of a rigid body move parallel to and in the same direction as every other point in the body

Quantity, such as velocity or force, that is completely specified by its magnitude and direction

Change in position of a body over time, expressed in linear (m/s) and angular (degrees/s) terms

Property of a material expressed by a changing stress-strain relationship over time

Gravitational force acting on a mass