Extension

Extension is a straightening movement that moves bones apart, as when the hand moves away from the shoulder. An exception applies to the shoulder joint: extension there is the return movement from shoulder-joint flexion. Source attributes the movement terminology to Thompson (1989).

Page 148 pairs this shoulder-joint exception with its representative exercises: "Extension — extends the humerus, draws the arm downward to the side. Exercise: dips, push-ups."

• Extension = straightening; moving bones apart.
• Example: hand moving away from the shoulder.
• Shoulder exception: extension is the return movement from shoulder flexion.
• Shoulder-joint extension's representative exercises: dips, push-ups (page 148).

• flexion — the opposite (bending) movement.
• spinal-column — spine performs extension as one of its movements.
• dip / push-up — the shoulder-joint-extension exercises page 148 pairs with this definition.