Stretching is so important for the health of our muscles. You may have one or more muscle groups that are extremely tight. Daily stretching helps improve the elasticity of your muscles.
The most common book I recommend to my patients is "Stretching" by Bob Anderson.
Here is a link to the book on Amazon :
https://www.amazon.com/dp/0936070463/ref=as_sl_pc_qf_sp_asin_til?tag=dradamrosen20-20&linkCode=w00&linkId=cd978fa288de370279a6c55f739f7770&creativeASIN=0936070463
As with any activity check with your health provider to make sure that it is safe for you to participate.
https://www.DrAdamRosen.com