The human body is designed for movement.  Our society has become more and more sedentary as a result of our job demands, lifestyle changes, and technology.  Holding any one posture for a prolonged period of time increases stiffness and tension.  As a result, sitting is a common cause of low back and neck pain.
The interesting thing is that manufacturers and various stores advertise that their chair will prevent back and neck pain.  To some degree they are correct.  We have several different styles, qualities, and structural chairs that may be better for one than another, however, there is no perfect chair, except the one you get out of frequently!
As a general rule you should avoid sitting for longer than 20 minutes without getting up.  The technique is simple.  By name it is only a micro-break.  However, if you sit for hours, then any length break may not be sufficient to help you avoid developing a neck or back problem. 
Perfect Posture
It is hard to avoid the negative effects of sitting for long periods of time and not aquire a poor posture position.  Just take a look at workers leaving an office building at the end of the day.  They look exhausted and all slumped forward.  Ideal posture is either vertical or slightly backwards in a rocking chair, but as a result of prolonged, constrained sitting postures the following occurs:  Upper back rolls forward, shoulders become shrugged, head pushed forward, chin pokes out, and chest breathing predominates over belly breathing.  It is no wonder that office workers have chronic mid back, neck pain, headaches, TMJ discomfort, rotator cuff syndromes, carpal tunnel syndromes, and breathing difficulties just to name a few. 
What can an individual begin to do in order to correct the poor postures.  First, be aware that our bodies adapt to demands placed upon them.  So, as you teach your body to be in a correct position, it may be uncomfotable at first.  Don't let this discourage you, continue through unless the ache turns in to other symptoms.  Second, there is a technique that will help you.  Perch at the edge of your chair, have your feet be slightly farther apart than your hips, tuck your chin in as if nodding "yes", rotate your arms outwards (palms forward or turned out), and breathe in/out in a slow, consistent pattern.  This can be performed once or twice for every 20-30 minutes of prolonged sitting.  A suggestion would be upon your return from a micro-break.

For a restful night, try these strategies:

  • Relieve lower-back pressure by putting a pillow under your knees. The pillow comfortably flexes your lower spine.
  • Try a pillow made with down instead of a foam pillow. You want a pillow that is low enough to support your head without flexing your neck, to avoid neck and shoulder aches. Orthopedic pillows with a scooped-out hollow for your head help support the neck and can also be helpful, especially if you have chronic neck problems.
  • Put enough blankets on your bed to stay warm. You may otherwise unconsciously curl up to keep warm, which can leave you with a sore back.
  • Allow yourself enough room to be able to move your arms and legs and roll over during the night. This is a natural way to prevent your joints from getting stiff.                          
                                                                                                                                    MSN Health & Fitness