a little background about me: im 5'7", 187lb. im well over 20% bf and pretty obese. however, i am fairly strong and been lifting weights for a good 5 months now. but i am no means a person with a great core level. as some of you may know already i have a difficult time running 1.5mi within 14min which, im currently working on. aside the running, i need to improve my abdominal work, sit-ups. my goal is to perform 38 sit-ups with arms crossed over chest within 1 minute. on my first attempt, i finished only at 22 sit-ups within the minute . i want to know what other exercises i should consider to improve my core level? i have the fitness ball laying around but havent used it ever since i joined the gym (5 months ago). so far, i been doing crunches/paced sit-ups and other abdominal machines to get my body used to it. so id like to ask what exercises or movements would you suggest for my goal? how many sets/reps/etc.