In this pose, the challenge is not the position itself, so much as its relationship to gravity. If it were rotated 45 degrees, it would just be the work of sitting vertically in dandasana (which can certainly present its own challenges).

Ideally, the weight in this pose is distributed between the sitting bones and the tailbone. All the weight should not be borne on the sacrum, because that would create a destabilizing counternutation in the sacroiliac joints.

If dandasana is a challenge because of tight hamstrings, that tightness will make it impossible to support this pose correctly with the legs straight. In this case, bending the knees so that the spine can remain neutral is a good option.

It is an interesting challenge to have to work hard to maintain a neutral spine, as posted to working to get the spine into flexion, extension, or rotation.

This asana is often described as working the abdominal muscles. This is true; however, the abdominal muscles do not hold the weight of the pose. Rather, they are modulators of the action, creating hip flexion, which is mainly performed by the psoas major and iliacus. If the psoas is difficult to access it is possible to overwork the rectus femoris and tensor fascia late. in this pose.

Just as bending the knees makes this pose easier by shortening the length of the lower lever arm, stretching the arms overhead would make it more difficult by lengthening the upper lever arm.