Long periods of tension, like long periods of exercise, create a kind of conditioning. These tensions tax the body and form the bodily basis for job stress, burnout, and medical consequences. This kind of self-conditioning also creates carpal tunnel syndrome. Thoracic Outlet Syndrome, which involves burning sensations and numbness down the arms, has the same origins. Lack of movement leads to stiffness.
Movement interrupts tension habits.
Conversely, lack of movement while under tension leads to conditioning into a state of tension. They get stiff on the job. The position most people adopt when working at the keyboard involves suspending their arms with bent elbows, hands over the keyboard. This position places strain on the muscles of the back and shoulders below the shoulder blades, which prevent the shoulders from rolling forward. Those muscles get tired and sore and produce mid-back pain.