Final answer:
The index for static posture, which is crucial for power training and good posture, involves aligning the center of gravity directly above the hips to avoid back strain and optimize power during athletic start-offs.
Step-by-step explanation:
The index for static posture that is also an important factor for power training refers to the body's center of gravity and its relationship to the hips pivot point. Good posture is characterized by someone standing or sitting with their center of gravity directly above the hip's pivot point, which is crucial to avoid back strain and disk damage. This alignment also plays a significant role during the start-offs in races for swimmers and athletes, as maintaining balance and posture affects the initial burst of power and performance in competitions.