My father has had problems with his muscles ever since he was young, but it has, apparently, worsened with age, despit his muscular built. What could it be?
His muscles seem to have trouble getting rid of lactic acid, which was measured in an exam and was extremely (and unusually) high after going up and down the stairs, for a prolonged period of time. This produces cramps and makes the muscles feel stiff, even to touch. When he was younger this would happen whenever he excercised, with a much higher intensity than normal. Now that he's on his early 50's, he can get it from repetitive movement, for example, opening bottles or even zapping. His muscles become stiff and go sloooowly back to normal.
He also has hypertension.
Any ideas of what illnesses could be causing this? None of his sisters or daughters have had this. He has no male direct relatives besides his deceased father, who, apparently (we never asked directly), didnt suffer from this, but had several back problems and even went through surgeries for it. His mother has hypertension, and it runs in the family.