These two questions have a lot in common. Obviously, only a health care professional can determine the source of your neck stiffness or pain. If there is no apparent trauma involved (like whiplash, a fall, or a sports injury), and if other conditions (tumor, infection, arthritis, etc.) have been ruled out, one of the most likely causes for chronic neck pain is poor posture.
Your body is similar to a moving chain, with your head, body, arms and legs linked together by joints, and supported by bones and soft tissues (muscles, ligaments, etc.). Movement at one joint influences movement at other joints in the chain.1 In fact, your feet can have a big influence on the rest of your body, especially if they are not in balance. Postural imbalance places stress and strain on body parts higher up, which can cause pain. Besides a foot problem, obesity can also contribute to postural conditions. Being overweight can cause stress pain to an area like the neck, as soft tissues must work all day against the downward pull of gravity.
Don't forget, your body has several postures, including a standing/walking posture, a sitting posture, and a reclining posture. Many "painful, disabling conditions of the soft tissues of the musculoskeletal system are directly or indirectly related to posture in standing, walking, moving, lying, sitting, bending, or lifting". 2 Relaxation of soft tissues during sleep puts the cervical spine (neck) at risk due to stress from poorly controlled movement and improper support. Improper sleep posture represents a form of sustained stress, which can lead to problems with the neck muscles and spine. For example, a person who sleeps on his/her stomach, or who sleeps on a pillow or stack of pillows that do not support the neck properly, can put excessive pressure on muscles and ligaments. To prevent spinal instability, these soft tissues have to work harder all night; as a result, they can be fatigued or irritated by morning.
Once you have been examined and your postural status evaluated, your healthcare professional can determine what treatment will best relieve your neck pain and help prevent your postural stresses from reoccurring. You may require spinal manipulation to restore your neck to its proper alignment and relieve stress pain.