We all know that when we are sick or feverish we also have headaches. General discomfort can also do the same. I know of a case of a girl who had tensions gripping her head when she meditates. It went off after regular exercise. It seems that she seldom exercised before.
Health is indeed a very important factor for good meditation.
On another occasion I discovered how one notes is also important. There is this person who fixes his eyes firmly as he walked. Even when sitting with eyes closed, he will still strain his eye muscles when he tries to concentrate. As a result stress builds up at the region of his forehead and eyes. Last but not least there is also the case of Kammic retribution.