| acromioclavicular joint | irregular joint between the acromion process of the scapula and the distal clavicle |
| active insufficiency | condition occurring when a two-joint muscle cannot shorten enough to cause full range of motion at both joints it crosses at the same time |
| 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 |
| 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 |
| 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 | a person’s ability to control equilibrium |
| ballistic stretching | a series of quick, bouncing-type stretches |
| base of support | area bound by the outermost regions of contact between a body and support surface or surfaces |
| bending | asymmetric loading that produces tension on one side of a body’s longitudinal axis and compression on the other side |
| Bernoulli principle | an expression of the inverse relationship between relative velocity and relative pressure in a fluid flow |
| biomechanics | application of mechanical principles in the study of living organisms |
| bone atrophy | decrease ... |