This study estimated the difficulty of various sit-ups tests using an item response theory (IRT) model, the Rasch Poisson Counts model. Scores were obtained on 18 sit-ups tests. All tests were thought to vary in difficulty based on clinical observations. Item difficulty was defined by the Poisson model as the difficulty of Step 1, where the difficulty of a step represented the difficulty of completing a sit-up. The difficulty values of the tests ranged from -4.02 to -3.57. The easiest test was executed with hands on thighs and feet anchored. Most tests had good fit values. The results demonstrated that a variety of sit-ups tests can provide a range of difficulties and variety in forming a sit-ups test bank.