I am having trouble doing sit ups.  I am crossing my arms across my chest and its hard for me to raise up to my knees.  I am wondering what I could do.  I have about 20 days to get into shape for a physical agility test and I can do everything but the sit ups.  I can barely get my shoulder off the ground.  The only way I could do them is put my feet under the couch and then its really hard.  Anyone have any suggestions let me know.
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