I have a problem! How can I get to do 75 sit-ups in one sitting??? Right now I can only knock out about 40 and I have no idea why. Either my abs or my thighs start to burn way too soon. I have till the beggining of April to get to 75. Any advice??? Oh and I'm not fat or have a gut, I do have ab diffinition but obviously that doesnt matter. Thanks in advance kids!