Martin seems to play too much on his devices. Furthermore, it isn't shocking to hear his back hurts. I would advise him to cut the game time he exerts in a row. In other words, he needs to stop playing games for that long straight. He should not play for 9 hours straight.
The main reason Martin's back aches is because of the lack of movement and placing his back on a surface for an extended amount of time.
If he takes breaks between his 6-hour game time, he would have done other activities causing him to move around.