Which of the following is a modification of the basic swan exercise?

The modification of the basic swan exercise that involves legs down is significant because it alters the level of extension and engagement of the back extensors. In the standard swan exercise, the legs are typically lifted to enhance the challenge to the back muscles and promote proper pelvic alignment. By keeping the legs down, the exercise becomes more accessible, allowing individuals to focus on spine extension and engaging the core without the added difficulty of leg lift. This modification can be particularly beneficial for beginners or those with limited range of motion, as it reduces the intensity while still promoting the essential principles of Pilates.

The other options, such as extending the arms further, looking upward, or increasing the speed, may exacerbate the challenge of the exercise rather than modifying its intensity or accessibility. These approaches could lead to improper form or strain and do not serve the purpose of tailoring the exercise for various fitness levels or needs. Therefore, the choice of legs down effectively addresses the need for modifications in the swan exercise.