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Rotation and supination do not increase or decrease the angle between bones.
To increase the angle of a joint is extension. To decrease the angle of a joint is flexion. (plato users the answer is A.)
Flexion decreases the angle between two bones in a joint. Extension increases that angle.
flexion decreases in angle between articulating bones extension increases in angle between articulation bones
To extend a muscle A MOTION IS MADE TO INCREASE AN ANGLE BETWEEN TWO BONES.
Extension.
Flexion is the general term for movements that decrease the angle between two bones; however, in the sagittal plane, the special term "adduction" is used for movements that decrease the angle between the limb and the midline.
Muscles move by contraction. When the cells shorten, the muscle pulls on the ligaments that connect the bones and the movable body parts. Depending on how a skeletal muscle acts, it may be classified as a flexor (decreases angle to joint) or an extensor (increases angle, straightening the joint).
Cartilage in joints REDUCE friction.
Concentric isometric contraction
Flexion is the act of bringing two bones closer together, decreasing the angle between the two bones. Extension is the act of increasing the angle between two bones, resulting in a straightening motion.
Muscles are attached to two different bones. When a muscle contracts, it shortens. When it shortens, the shortens the angle between the two bones causing movement.