I had my right leg in the chair and reclined my chair wondering if this position would stretch my right hamstring and or left hip flexor. Thoughts? But while reclined I flexed my core / ab area and held it. I know it only looks like I'm lifting my head and shoulders but my core area was working hard to hold the position. This video was my 3rd set of holding it for 100 seconds. Thoughts? Is this exercise worth adding to my routine? If so what would the benefits and gains possibilities be and how many days a week and how many sets? And would both legs up stretch both hamstrings? Appreciate all feedback and ideas. https://youtu.be/NaBSf2p9Rv8