Final answer:
The muscle trait characterized by the ability to shorten and initiate movement upon stimulation is known as contractility, which is essential for muscle function including the contraction phase.
Step-by-step explanation:
The muscle trait that has the ability to shorten and produce movement when stimulated is known as contractility. This is a fundamental property of muscle tissue that allows it to pull on its attachment points and shorten with force. The process in which muscle fibers use their protein filaments, actin and myosin, to slide past one another leading to shortening of the muscle is called contraction. This property is vital for all types of muscle tissues including skeletal muscle, smooth muscle, and voluntary muscle, and plays a crucial role during the contraction phase. Various phases of contraction include the twitch contraction phase when tension increases, and it's essential for producing movement and maintaining posture and stability.