Why does sitting at a desk all day make us so tired? Do you feel fatigued, sore or head achy after a long day's work behind a computer? Osteopath Etienne explains the physical mechanics and pitfalls of an immobile and faulty posture at work. What is it? How unpleasant is it to feel physically run down or achy after spending a day at work being immobile most of the time. As a result symptoms often are chronic lower back pain (dull ache, soreness, tightness, stiffness, etc..),