Maybe you are pregnant? Bloated? Muscle typically takes up less space than fat so.... I am at a loss. Biking for me definately made me lose thigh and rump spread. If you have been riding and exercising for a short period of time, I would not worry just yet. But definately look into all aspects of what you are doing, including eating habits, caffiene intake, salt intake, etc. I know for me if I OD on salt and or caffiene, my otherwise loose pants feel abit snug.....