Hi @mayblin, On Nov 7 in an email , Dr. Fishman wrote that doing Supta Padangusthasana I three times a day improved the lumbar spine of two participants:

SURPRISE!
Doing Supta Padangusthasana I three times a day has improved these two people's spines quite a bit more than what we usually see.
We had thought it would be best for the femur or hip: it is good for them, but its greatest benefit appears to be for the spine!

FYI,
Teri