― How to strengthen the hip flexors and abdominal muscles without spending money? How to have flat stomach? The answer is do sit ups. This exercise is very good for women. Sit-ups can be carried out wherever you are, sit ups is easy to do but one of the benefit is to get flat stomach. Here are pictures collection of Sit Ups and how to do it. ∙ Source: colombiaherida.org via Megami on Pinterest ∙ Source: fatburningtips4women.com via Megami on Pinterest ∙ Source: [...].