-- Posted by Anonymous at 4:36 pm on June 29, 2008 ok so ive been doing alot of warmup rountines and trampolining and things but today my stomach looks alot slimmer and my belly is really sore in certain ways i move is this the muscles or can anyone help what it could be -- Posted by morik at 4:38 pm on June 29, 2008 By tramplolining a lot you are probably using muscles you haven't used much before. Therefore making them tired. Slow down a bit. -- Posted by MXfreak at 4:38 pm on June 29, 2008 your body is building more muscle -- Posted by nyc93 at 4:39 pm on June 29, 2008 ur just working out muscles ur body isn't normally working out -- Posted by chicklover at 4:41 pm on June 29, 2008 when you work out more then your use to you feel really sore afterwards then muslce builds -- Posted by brown eyed girl at 5:26 pm on June 29, 2008 you are using muscles you don't use often.