Any clinical trial has the problem that the doctor and patient experience the treatment as a blessing which changes how the patient perceives their condition and how the doctor perceives the patient. That's the magic of blessings!
In general pain is a signal that you should take it easy on the affected part, but that's not true of back pain most of the time. There probably is a real lesion or a mechanical conflict [1] but the brain plays a big role in interpreting their signals and can make emotional conflicts about work and other duties explode.
The old advice that you should get bed rest is terrible because it leads to muscle wasting and loss of flexibility and degrades the performance of the back as a system, almost any kind of activity that doesn't bring up emotional conflicts is a win.
[1] see https://www.amazon.com/dp/0987650408 -- at risk of putting words in his mouth, McKenzie thinks back pain is often a lack of flexibility, you feel uncomfortable because your muscles are pushing against each other. I've had good luck stretching my lower back with "The Cobra" exercise from yoga but I like Lowen's "Bioenergetic arch" even better.