Load-bearing disorder refers to pain from load on the joint. Lifting may not be the main factor. Sitting in one position for long periods of time is more likely the problem load.
It's really true that motion is lotion. Joints stiffen up without regular, rhythmic movement. Muscles must contract and relax in order to move blood along and get rid of any toxins that build up from inactivity.
Nontraumatic neck pain can be classified as a load bearing disorder or a movement impairment disorder. The difference is based on what causes the painful symptoms: load or movement?
With load-bearing disorders, you are more likely to have pain but full motion when you do move your neck. With movement impairment, there's pain and a loss of motion. According to a recent study on neck pain patients in Australia, you can expect a faster recovery with a load-bearing disorder compared to movement impairment disorder.