contortionist hanbook exercises + pilates is a good start for most but not all people
conortionist handbook shows how to start at a beginner level and work your way up to a contortionist level gradually and safely
There are various editions online and it is free
Problem with statistics is they do not work on an individual level
What they might do is take the average pain level of a group of individuals who did an exercise vs a control group who did not do the exercise
They then compare the average pain level and if it increased or decreased over a certain amount of time and if the control group saw a similar change
The problem is the repeatedly doing same exercise might increase pain for 1 person in the group a month later but decrease pain for another person but they just go by the average
Once you found a exercise routine that decreases in pain from the first week to the second week when duration, intensity and frequency is the same then you can gradually increase duration by 10% per week aa long as the intensity of the pain remains the same or decreases but if the intensity of the pain increases then you should do a different exercise
Once you can not increase duration due to time limits you can increase intensity and lower the duration and start over again