I am gererally very healthy person, very rarely sick and if i get a cold, i get a croaky throat and little phlem and after a few days of cold and flu tablets I m fine. My company also every year gives us the flu shot. I have now had the flu for about 6 days, was most sever on day 3, it is tapering down and i m back to work today, however on about day 5 i found my upper and lower legs and my buttocks were sore as if i d just ran 20km s and stayed tight and sore still, also they appear to be so tight they are bigger and seem to have grown or i am retaining water or something.. Any thoughts?