Is physical therapy the best remedy for a back, lumbar strain, and/or sprain injury?

It is a good one: I guess that depends on who is answering this question but it is an appropriate choice & a good one, it is not the best as there are other options including, rest, activity modification, medication, massage, heat and/or ice applications, a simple back support or chiropractic as well as even acupuncture. It is a good way to learn back exercises & correct biomechanics to avoid a recurrence.