Cable rows form?

Mellouk89

Is doing the cable rows like this dangerous? I thought about doing it in this matter to stretch the back muscles and also for the purpose of strengthening my lower back. I tried it yesterday and I didn't feel any pain on the contrary I felt an increase in flexibility in my lower back, what are your thoughts?

https://www.youtube.com/watch?v=QGnC_iXKtdQ&list=FLJn_6E-fCZzr9UFJvoDQNDQ

Mellouk89