Back pain during the sleep can have different origins. There are 2 possible explanations for your pain. One explanation could be that a vertebral disc is irritated and that the inflammation process, which is most active during the night, makes you experience pain. The disc also bulges more when the back is rested. The increased in bulging may increase the pressure to the spinal nerves which brings on the pain.
The second possibilit is when your back is hyperlordotic (this means that the inward curve of your lower back is greater than it should be), the pressure on the facet joints are increased. Most people who have a hyperlordotic lower back experience pain or discomfort when lying prone on their stomach or supine on their back.
In prone-lying this is due to the fact that gravity is putting more weight on the joints. When laying on your back, shorterned muscles in your lower back could pull your facet joints towards each other. Both positions will irritate the surface of the joint and cause you discomfort. Lying on the side with the legs slightly curl may be a more comfortable position.
Like in all joints of the body, movement relieves pain due to the production of a lubricating fluid that is there to avoid this friction. When you wake up, you start moving your back more than during your sleep, which explains why the pain starts wearing off.
The longer you sleep, the stiffer your joints become which makes it more uncomfortable for you when waking up.
The second point you mention about going to the gym in the past is very interesting. Like I mentioned before, shortened muscles in the lower back increases the hyperlordosis. When the abdominal muscles are weakened in comparison with the lower back muscles, it puts the back into further lordosis, increasing the pressure on the joints.
Before, when you were going to the gym on frequent base, you were probably training your abdominal muscles more. These abdominal exercises created tension from the front of your body which decreased the hyperlordosis in your back. Now that you have stopped doing these exercises, you lower back muscles are getting dominant and are having the possibility to pull your back even more in lordosis.
What you can try doing to see if this theory is right, is strengthening your lower abdominal muscles and releasing the tension of your lower back muscles with stretches and deep tissue massage. Do this consistently for about a month and this will probably have a positive effect on your night pain.
With kind regards,
Luc Ortelli Read More At : ...