What is a modification for any long sitting series, including arm sitting series and spine twist?

Bending the knees during a long sitting series, including arm sitting series and spine twist, serves as an effective modification for individuals experiencing hamstring tightness. When someone has tight hamstrings, sitting with the legs fully extended can create strain, leading to discomfort or poor posture during the exercise. By bending the knees, the participant reduces this tension and can focus on proper alignment and movement without compromising their comfort or risking injury. This adjustment enables them to engage more effectively with the core and upper body movements while maintaining a balanced position.

The other options do not address the needs of someone with hamstring tightness effectively. Raising the arms higher may increase strain on the shoulders or the back without alleviating the discomfort caused by tight hamstrings. Crossing the legs could also shift the focus away from the intended exercise and might not provide stability for the lower back. Finally, keeping the back straight and rigid could lead to additional tension and discomfort, especially if the hamstrings are tight, which may hinder the overall effectiveness of the exercise series.