That familiar feeling when the workday seems to be over, but your head feels heavy, your eyes burn, and even after a normal night’s sleep there is still no energy? Physically, it seems like you have not really been working – the whole day was spent in a comfortable chair in front of a monitor, yet by evening you feel completely drained. Most people put it down to overwork or a lack of vitamins, but the real reason lies in how our body reacts to sitting in front of a screen every day.