@sjam
Can you share with us the isometric ab exercises and hip flexor stretches you used?
I did any ab exercise that I felt like doing: all kind of planks, ab-wheel rollouts, L-sit, hollow body holds, etc. The idea was to activate my abs, not to increase strength, size, or anything. With only one set close to failure I could feel my core more tight.
Regarding hip flexor stretches, I did mostly two: the couch stretch and the standing quad stretch. Whichever you chose, remember to do them with a posterior pelvic tilt.
Any recommended reading to learn the fundamentals of creating a similar routine? I would love to create something similar for bridge work but have no clue what to do/where to start.
This is a synthesis of years of disorganized learning. I do recommend
Cirque Physio, several Youtube channels (Emmet Louis, Kit Laughlin, Ian Markow, etc.) and doing research in scientific journals. There's relatively few information on how to increase flexibility, compared to how to gain size or strength.
BTW, I wouldn't use this approach for bridges. The pike involves only one joint; the bridge involves many, including the spine. It's more dangerous to do something like this. However, you could use this routine as a template for increasing hip extension or shoulder flexion, and I think you'd see good results.
