Final answer:
Feet elevated push-up is a variation of the traditional push-up; other variations also include weighted push-ups, ring push-up, and push-up holds, each with different challenges regarding the force exerted on the center of gravity and muscle engagement.
Step-by-step explanation:
The exercise that is a variation of the push-up is A) Feet elevated push-up. Other variations such as weighted push-ups, ring push-up, and push-up holds also offer different levels of intensity or stability challenges, but the core movement is derived from the traditional push-up. In each of these exercises, the forces involved in doing push-ups come into play, where a person's weight acts as a force exerted downward on their center of gravity (CG). The variations can affect how this force is distributed and what muscles are targeted or engaged more intensively.
For instance, with feet elevated push-ups, changing the angle of the body increases the force required from the upper body and shoulders due to a higher percentage of body weight being shifted towards the arms. Weighted push-ups would increase the overall force exerted downward, requiring more strength to push up. In-ring push-ups, the instability of the rings increases the challenge for the core and shoulder stabilizers. Finally, push-up holds focus on maintaining a static position, emphasizing the muscles' isometric strength.