Is caused by a number of reasons, it is however exaggerated by tight muscles & poor flexibility.
Main cause of back pain:
If you are sitting in a fixed position for a long period of time. Your body will adapt to this position by tightening your muscles.
The problem of this however is your back will then be stiff and painful when you are in other positions.
Unfortunately we can’t expect our body’s to be flexible, upright and able to move freely if we spend the majority of our time sat or laying down.
The solution is to be more active and stretch daily. A daily stretching plan after some activity like a walk or jog will massively reduce back pain. Yoga is also perfect for this.
Please take it slowly and build up gradually, also consult your doctor or physio if you have a injury.