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Absolute angle Angular orientation of a body segment with respect to a fixed line of reference

Acromioclavicular joint Irregular joint between the acromion process of the scapula and the distal clavicle

Active insufficiency Limited ability of a two-joint muscle to produce force when joint position places the muscle on slack

Active stretching Stretching of muscles, tendons, and ligaments produced by active development of tension in the antagonist muscles

Acute loading Application of a single force of sufficient magnitude to cause injury to a biological tissue

Agonist Role played by a muscle acting to cause a movement

Amenorrhea Cessation of menses

Anatomical reference position Erect standing position with all body parts, including the palms of the hands, facing forward; considered the starting position for body segment movements

Angle of attack Angle between the longitudinal axis of a body and the direction of the fluid flow

Angle of projection The direction at which a body is projected with respect to the horizontal

Angular Involving rotation around a central line or point

Angular acceleration Rate of change in angular velocity

Angular displacement Change in the angular position or orientation of a line segment

Angular impulse Change in angular momentum equal to the product of torque and time interval over which the torque acts

Angular momentum Quantity of angular motion possessed by a body; measured as the product of moment of inertia and angular velocity

Angular velocity Rate of change in the angular position or orientation of a line segment

Anisotropic Exhibiting different mechanical properties in response to loads from different directions

Annulus fibrosus Thick, fibrocartilaginous ring that forms the exterior of the intervertebral disc

Antagonist Role played by a muscle acting to slow or stop a movement

Anteroposterior axis Imaginary line around which frontal plane rotations occur

Anthropometric Related to the dimensions and weights of body segments

Apex The highest point in the trajectory of a projectile

Appendicular skeleton Bones composing the body appendages

Archimedes’ principle Physical law stating that the buoyant force acting on a body is equal to the weight of the fluid displaced by the body

Articular capsule Double-layered membrane that surrounds every synovial joint

Articular cartilage Protective layer of dense white connective tissue covering the articulating bone surfaces at diarthrodial joints

Articular fibrocartilage Soft-tissue discs or menisci that intervene between articulating bones

Average Occurring over a designated time interval

Axial Directed along the longitudinal axis of a body

Axial skeleton The skull, vertebrae, sternum, and ribs

Axis of rotation Imaginary line perpendicular to the plane of rotation and passing through the center of rotation

Balance Ability to control equilibrium

Ballistic stretching A series ...

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